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Author name code: harra
ADS astronomy entries on 2022-09-14
author:"Harra, Louise K."
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Title: What drives decayless kink oscillations in active region
coronal loops on the Sun?
Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter,
Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David;
Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle,
Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis;
Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel;
Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J.
2022arXiv220904251M Altcode:
We study here the phenomena of decayless kink oscillations in a system
of active region (AR) coronal loops. Using high resolution observations
from two different instruments, namely the Extreme Ultraviolet Imager
(EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly
(AIA) on board the Solar Dynamics Observatory, we follow these AR
loops for an hour each on three consecutive days. Our results show
significantly more resolved decayless waves in the higher-resolution
EUI data compared with the AIA data. Furthermore, the same system of
loops exhibits many of these decayless oscillations on Day-2, while on
Day-3, we detect very few oscillations and on Day-1, we find none at
all. Analysis of photospheric magnetic field data reveals that at most
times, these loops were rooted in sunspots, where supergranular flows
are generally absent. This suggests that supergranular flows, which
are often invoked as drivers of decayless waves, are not necessarily
driving such oscillations in our observations. Similarly, our findings
also cast doubt on other possible drivers of these waves, such as a
transient driver or mode conversion of longitudinal waves near the loop
footpoints. In conclusion, through our analysis we find that none of
the commonly suspected sources proposed to drive decayless oscillations
in active region loops seems to be operating in this event and hence,
the search for that elusive wave driver needs to continue.
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Title: Spatial distribution of jets in solar active regions
Authors: Odermatt, J.; Barczynski, K.; Harra, L. K.; Schwanitz, C.;
Krucker, S.
2022A&A...665A..29O Altcode: 2022arXiv220709923O
Context. Solar active regions are known to have jets. These jets are
associated with heating and the release of particles into the solar
wind. <BR /> Aims: Our aim is to understand the spatial distribution
of coronal jets within active regions to understand if there is a
preferential location for them to occur. <BR /> Methods: We analysed
five active regions using Solar Dynamics Observatory Atmospheric
Imaging Assembly data over a period of 2-3.5 days when the active
regions were close to disk centre. Each active region had a different
age, magnetic field strength, and topology. We developed a methodology
for determining the position and length of the jets. <BR /> Results:
Jets are observed more frequently at the edges of the active regions
and are more densely located around a strong leading sunspot. The
number of coronal jets for our active regions is dependent on the
age of the active region. The older active regions produce more jets
than younger ones. Jets were observed dominantly at the edges of the
active regions, and not as frequently in the centre. The number of
jets is independent of the average unsigned magnetic field and total
flux density in the whole active region. The jets are located around
the edges of the strong leading sunspot.
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Title: The Solaris Solar Polar MIDEX-Class Mission Concept: Revealing
the Mysteries of the Sun's Poles
Authors: Hassler, Donald M.; Harra, Louise K.; Gibson, Sarah; Thompson,
Barbara; Gusain, Sanjay; Berghmans, David; Linker, Jon; Basu, Sarbani;
Featherstone, Nicholas; Hoeksema, J. Todd; Viall, Nicholeen; Newmark,
Jeffrey; Munoz-Jaramillo, Andres; Upton, Lisa A.
2022cosp...44.1528H Altcode:
Solaris is an exciting, innovative & bold mission of discovery to
reveal the mysteries of the Sun's poles. Solaris was selected for Phase
A development as part of NASA's MIDEX program. Solaris builds upon
the legacy of Ulysses, which flew over the solar poles, but Solaris
provides an entirely new feature remote sensing, or IMAGING. Solaris
will be the first mission to image the poles of the Sun from ~75
degrees latitude and provide new insight into the workings of the
solar dynamo and the solar cycle, which are at the foundation of our
understanding of space weather and space climate. Solaris will also
provide enabling observations for improved space weather research,
modeling and prediction with time series of polar magnetograms and
views of the ecliptic from above, providing a unique view of the
corona, coronal dynamics, and CME eruption. To reach the Sun's poles,
Solaris will first travel to Jupiter, and use Jupiter's gravity to
slingshot out of the ecliptic plane, and fly over the Sun's poles
at ~75 degrees latitude. Just as our understanding of Jupiter &
Saturn were revolutionized by polar observations from Juno and Cassini,
our understanding of the Sun will be revolutionized by Solaris.
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Title: Plasma flows in different magnetic environments on the Sun
Authors: Harra, Louise K.
2022cosp...44.2408H Altcode:
The Sun, as a magnetic star, has dynamics and complex structures on
all scales. There are flows throughout the solar atmosphere from the
surface to the outer solar atmosphere (and into the solar wind). In
this review, we will discuss from the smallest scale flows seen,
to the most dramatic flows in coronal mass ejections. The smallest
scale phenomena such as jets, plumes and small brightenings such as
those seen in the Solar Orbiter 'campfires' all have possibilities to
flow into the solar wind. The latest results from Parker Solar Probe
has provided tantalising predictions of when the magnetic switchbacks
seen in the solar wind originate - on the network boundaries where
many of these small-scale flows are seen. Moving to the large size
scale flows, with the large flares, and coronal mass ejections, the
flows start in the pre-trigger phase on a small size scale, and expand
across the Sun, creating a huge impact in the solar wind. The current
status will be reviewed.
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Title: A spectral solar irradiance monitor (SoSpIM) on the JAXA
Solar-C (EUVST) space mission
Authors: Harra, Louise K.; Watanabe, Kyoko; Haberreiter, Margit;
Hori, Tomoaki; Hara, Hirohisa; Kretzschmar, Matthieu; Woods, Thomas;
Shimizu, Toshifumi; Krucker, Samuel; Berghmans, David; Jin, Hidekatsu;
Dominique, Marie; Eparvier, Francis G.; Gissot, Samuel; Leng Yeo, Kok;
Pfiffner, Dany; Milligan, Ryan; Thiemann, Edward; Miyoshi, Yoshizumi;
Imada, Shinsuke; Kawate, Tomoko; Chamberlin, Phillip; Rozanov, Eugene;
Silvio Koller, -.; Barczynski, Krzysztof; Nozomu; Nishitani; Ieda,
Akimasa; Langer, Patrick; Meier, Leandro; Tye, Daniel; Alberti, Andrea
2022cosp...44..834H Altcode:
The JAXA Solar-C (EUVST) mission (Shimizu et al., 2020) is designed
to comprehensively understand how mass and energy are transferred
throughout the solar atmosphere. The EUV High-Throughput Spectroscopic
Telescope (EUVST) onboard does this by observing all the temperature
regimes of the atmosphere from the chromosphere to the corona
simultaneously. To enhance the EUVST scientific capabilities,
there will be a Solar Spectral Irradiance Monitor (SoSpIM). SoSpIM
will work hand-in-hand scientifically with EUVST, by providing the
full Sun irradiance at sub-second time cadence combined with the
spatially resolved spectroscopy from EUVST. The SoSPIM instrument
will specifically address two aspects. These are: · Understand how
the solar atmosphere becomes unstable, releasing the energy that
drives solar flares - achieved through probing fast time cadence
solar flare variations. · Measuring solar irradiance that impacts
the Earth's thermosphere and the mesosphere, linking to spatially
resolved measurements of the solar atmosphere with EUVST. SoSpIM will
provide high time resolution measurements in 2 channels (a) in the
corona through channel 1 (EUV) and (b) in the lower atmosphere through
channel 2 (Lyman alpha). Each channel impacts different layers of the
Earth's atmosphere.
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Title: How Can Solar-C/SOSPIM Contribute to the Understanding of
Quasi-Periodic Pulsations in Solar Flares?
Authors: Dominique, Marie; Harra, Louise K.; Watanabe, Kyoko; Hara,
Hirohisa; Zhukov, Andrei; Shimizu, Toshifumi; Berghmans, David;
Dolla, Laurent; Gissot, Samuel; Pfiffner, Dany; Imada, Shinsuke;
Silvio Koller, -.; Meier, Leandro; Tye, Daniel; Alberti, Andrea
2022cosp...44.2524D Altcode:
Quasi-periodic pulsations (QPPs) refer to nearly-periodic oscillations
that are often observed in irradiance time series during solar flares
and have also been reported in several stellar flares. In the last
years, several statistical studies based on Soft X-ray measurements
have reached the conclusion that QPPs are present in most solar
flares of class M and above. Still, as of today, we are still unsure
of what causes QPPs. Several models could explain the presence of
QPPs with periods matching the ones observed. More detailed analysis
of the observational signatures of QPPs might help determine which
of those models are actually playing a role in the generation of
QPPs. However, as QPPs is a small timescale process (the period of
QPPs is often reported to be less than a minute), such an analysis
requires instruments with a good signal-to-noise and high sampling
rate. In this context, the spectral solar irradiance monitor SOSPIM,
that will be part of the JAXA SOLAR C mission and that will complement
the EUVST spectrograph measurements, could be a valuable asset. SOSPIM
will observe the solar chromosphere and corona in the Lyman-alpha
and EUV spectral ranges at high cadence. In this presentation, we
review the current knowledge of QPPs and describe what could be the
contribution of SOSPIM to push their understanding one step forward.
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Title: Heating during small solar flares with Solar Orbiter STIX,
Hinode and SDO.
Authors: Harra, Louise K.; Reeves, Kathy; Krucker, Sam; Barczynski,
Krzysztof; Battaglia, Andrea; Collier, Hannah
2022cosp...44.2525H Altcode:
One of the key aspects of solar flares is how, where and how fast
plasma is heated. Spectroscopic observations are constrained by the
duration it takes to build up an image and hence the time resolution
is often of the order of 5 minutes during a flare. To obtain higher
cadence spectroscopic information, it is also possible to use the wide
slot (260") - or 'overlappogram' data. An observing campaign (HOP361)
was carried out in October using Hinode EIS, XRT and coordinating
with Solar Orbiter STIX. The campaign was carried out at high time
cadence and was telemetry intensive. SDO is also of key interest to
these observations. On the 8th October, a B2 classfication flare took
place, and was observed by all instruments. The EIS 'overlappogram'
allows high time cadence observations (10 secs) of the whole active
region. During this flare, it is possible to extract information on
the hot plasma from Fe XXIV, STIX and XRT. There was a smaller flare
which wasn't registered by GOES that followed, that provides a contrast
example that doesn't show clear hot emission.
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Title: Automatic detection of small-scale EUV brightenings observed
by the Solar Orbiter/EUI
Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.;
Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin,
É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.;
Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti,
S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.;
Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N.
2022A&A...663A.128A Altcode: 2022arXiv220404027A
Context. Accurate detections of frequent small-scale extreme ultraviolet
(EUV) brightenings are essential to the investigation of the physical
processes heating the corona. <BR /> Aims: We detected small-scale
brightenings, termed campfires, using their morphological and
intensity structures as observed in coronal EUV imaging observations
for statistical analysis. <BR /> Methods: We applied a method based
on Zernike moments and a support vector machine (SVM) classifier
to automatically identify and track campfires observed by Solar
Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA). <BR /> Results: This method
detected 8678 campfires (with length scales between 400 km and 4000 km)
from a sequence of 50 High Resolution EUV telescope (HRI<SUB>EUV</SUB>)
174 Å images. From 21 near co-temporal AIA images covering the same
field of view as EUI, we found 1131 campfires, 58% of which were
also detected in HRI<SUB>EUV</SUB> images. In contrast, about 16%
of campfires recognized in HRI<SUB>EUV</SUB> were detected by AIA. We
obtain a campfire birthrate of 2 × 10<SUP>−16</SUP> m<SUP>−2</SUP>
s<SUP>−1</SUP>. About 40% of campfires show a duration longer than 5
s, having been observed in at least two HRI<SUB>EUV</SUB> images. We
find that 27% of campfires were found in coronal bright points and
the remaining 73% have occurred out of coronal bright points. We
detected 23 EUI campfires with a duration greater than 245 s. We found
that about 80% of campfires are formed at supergranular boundaries,
and the features with the highest total intensities are generated at
network junctions and intense H I Lyman-α emission regions observed
by EUI/HRI<SUB>Lya</SUB>. The probability distribution functions for
the total intensity, peak intensity, and projected area of campfires
follow a power law behavior with absolute indices between 2 and 3. This
self-similar behavior is a possible signature of self-organization,
or even self-organized criticality, in the campfire formation
process. <P />Supplementary material (S1-S3) is available at <A
href="https://www.aanda.org/10.1051/0004-6361/202243257/olm">https://www.aanda.org</A>
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Title: Searching for a Solar Source of Magnetic-Field Switchbacks
in Parker Solar Probe's First Encounter
Authors: de Pablos, D.; Samanta, T.; Badman, S. T.; Schwanitz, C.;
Bahauddin, S. M.; Harra, L. K.; Petrie, G.; Mac Cormack, C.; Mandrini,
C. H.; Raouafi, N. E.; Martinez Pillet, V.; Velli, M.
2022SoPh..297...90D Altcode:
Parker Solar Probe observations show ubiquitous magnetic-field reversals
closer to the Sun, often referred to as "switchbacks". The switchbacks
have been observed before in the solar wind near 1 AU and beyond, but
their occurrence was historically rare. PSP measurements below ∼ 0.2
AU show that switchbacks are, however, the most prominent structures
in the "young" solar wind. In this work, we analyze remote-sensing
observations of a small equatorial coronal hole to which PSP was
connected during the perihelion of Encounter 1. We investigate whether
some of the switchbacks captured during the encounter were of coronal
origin by correlating common switchback in situ signatures with remote
observations of their expected coronal footpoint. We find strong
evidence that timescales present in the corona are relevant to the
outflowing, switchback-filled solar wind, as illustrated by strong
linear correlation. We also determine that spatial analysis of the
observed region is optimal, as the implied average solar-wind speed
more closely matches that observed by PSP at the time. We observe that
hemispherical structures are strongly correlated with the radial proton
velocity and the mass flux in the solar wind. The above findings suggest
that a subpopulation of the switchbacks are seeded at the corona and
travel into interplanetary space.
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Title: Constraining Global Coronal Models with Multiple Independent
Observables
Authors: Badman, Samuel T.; Brooks, David H.; Poirier, Nicolas;
Warren, Harry P.; Petrie, Gordon; Rouillard, Alexis P.; Nick Arge,
C.; Bale, Stuart D.; de Pablos Agüero, Diego; Harra, Louise; Jones,
Shaela I.; Kouloumvakos, Athanasios; Riley, Pete; Panasenco, Olga;
Velli, Marco; Wallace, Samantha
2022ApJ...932..135B Altcode: 2022arXiv220111818B
Global coronal models seek to produce an accurate physical
representation of the Sun's atmosphere that can be used, for example, to
drive space-weather models. Assessing their accuracy is a complex task,
and there are multiple observational pathways to provide constraints
and tune model parameters. Here, we combine several such independent
constraints, defining a model-agnostic framework for standardized
comparison. We require models to predict the distribution of coronal
holes at the photosphere, and neutral line topology at the model's outer
boundary. We compare these predictions to extreme-ultraviolet (EUV)
observations of coronal hole locations, white-light Carrington maps of
the streamer belt, and the magnetic sector structure measured in situ
by Parker Solar Probe and 1 au spacecraft. We study these metrics for
potential field source surface (PFSS) models as a function of source
surface height and magnetogram choice, as well as comparing to the more
physical Wang-Sheeley-Arge (WSA) and the Magnetohydrodynamic Algorithm
outside a Sphere (MAS) models. We find that simultaneous optimization
of PFSS models to all three metrics is not currently possible, implying
a trade-off between the quality of representation of coronal holes
and streamer belt topology. WSA and MAS results show the additional
physics that they include address this by flattening the streamer belt
while maintaining coronal hole sizes, with MAS also improving coronal
hole representation relative to WSA. We conclude that this framework
is highly useful for inter- and intra-model comparisons. Integral to
the framework is the standardization of observables required of each
model, evaluating different model aspects.
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Title: Observation of Magnetic Switchback in the Solar Corona
Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco;
Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta,
Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman;
Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia;
Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto;
Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania;
Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero;
Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati,
Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio;
Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère,
Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise;
Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna;
Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo;
Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N.
2022arXiv220603090T Altcode:
Switchbacks are sudden, large radial deflections of the solar wind
magnetic field, widely revealed in interplanetary space by the Parker
Solar Probe. The switchbacks' formation mechanism and sources are still
unresolved, although candidate mechanisms include Alfvénic turbulence,
shear-driven Kelvin-Helmholtz instabilities, interchange reconnection,
and geometrical effects related to the Parker spiral. This Letter
presents observations from the Metis coronagraph onboard Solar Orbiter
of a single large propagating S-shaped vortex, interpreted as first
evidence of a switchback in the solar corona. It originated above
an active region with the related loop system bounded by open-field
regions to the East and West. Observations, modeling, and theory provide
strong arguments in favor of the interchange reconnection origin of
switchbacks. Metis measurements suggest that the initiation of the
switchback may also be an indicator of the origin of slow solar wind.
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Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.;
Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.;
Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.;
Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long,
D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca,
L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.;
Jacques, L.; Berghmans, D.
2021A&A...656A..35Z Altcode: 2021arXiv210902169Z
Context. The three-dimensional fine structure of the solar atmosphere
is still not fully understood as most of the available observations
are taken from a single vantage point. <BR /> Aims: The goal of the
paper is to study the three-dimensional distribution of the small-scale
brightening events ("campfires") discovered in the extreme-UV quiet Sun
by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter. <BR />
Methods: We used a first commissioning data set acquired by the EUI's
High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and
we combined it with simultaneous data taken by the Atmospheric Imaging
Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171
Å passband. The two-pixel spatial resolution of the two telescopes
is 400 km and 880 km, respectively, which is sufficient to identify
the campfires in both data sets. The two spacecraft had an angular
separation of around 31.5° (essentially in heliographic longitude),
which allowed for the three-dimensional reconstruction of the campfire
position. These observations represent the first time that stereoscopy
was achieved for brightenings at such a small scale. Manual and
automatic triangulation methods were used to characterize the campfire
data. <BR /> Results: The height of the campfires is located between
1000 km and 5000 km above the photosphere and we find a good agreement
between the manual and automatic methods. The internal structure of
campfires is mostly unresolved by AIA; however, for a particularly
large campfire, we were able to triangulate a few pixels, which are
all in a narrow range between 2500 and 4500 km. <BR /> Conclusions: We
conclude that the low height of EUI campfires suggests that they belong
to the previously unresolved fine structure of the transition region and
low corona of the quiet Sun. They are probably apexes of small-scale
dynamic loops heated internally to coronal temperatures. This work
demonstrates that high-resolution stereoscopy of structures in the
solar atmosphere has become feasible.
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Title: Linking solar activity to solar wind: challenges and future
observations.
Authors: Harra, Louise
2021AGUFMSH15D2052H Altcode:
The current era of solar physics missions is opening up new ways to
view the Sun, from the sources of solar wind, to direct measurements at
varying distances from the Sun. Parker Solar Probe (PSP) has already
reached closer to the Sun than ever before. Solar Orbiter will start
its nominal science mission in December 2021. In this review, I will
discuss the activity on the Sun, from the smallest scales, that could
be contributing to the solar wind. I will discuss the attempts made to
link remote sensing and in-situ observations, and the challenges that
are faced. Spectroscopic observations hold particular value due to
the measurements of speeds and abundances, but have a small field of
view. Combined with imaging data and modelling efforts, understanding
what could flow into the solar wind is a key task for the solar and
heliospheric communities in the next years. Higher resolutions, and
new datatypes open new ways to explore the sources of the solar wind.
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Title: Probing Upflowing Regions in the Quiet Sun and Coronal Holes
Authors: Schwanitz, Conrad; Harra, Louise; Raouafi, Nour E.; Sterling,
Alphonse C.; Moreno Vacas, Alejandro; del Toro Iniesta, Jose Carlos;
Orozco Suárez, David; Hara, Hirohisa
2021SoPh..296..175S Altcode: 2021arXiv211012753S
Recent observations from Parker Solar Probe have revealed that the
solar wind has a highly variable structure. How this complex behaviour
is formed in the solar corona is not yet known, since it requires
omnipresent fluctuations, which constantly emit material to feed
the wind. In this article we analyse 14 upflow regions in the solar
corona to find potential sources for plasma flow. The upflow regions
are derived from spectroscopic data from the EUV Imaging Spectrometer
(EIS) on board Hinode determining their Doppler velocity and defining
regions which have blueshifts stronger than −6 kms−<SUP>1</SUP>. To
identify the sources of these blueshift data from the Atmospheric
Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI),
on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope
(XRT), on board Hinode, are used. The analysis reveals that only 5 out
of 14 upflows are associated with frequent transients, like obvious
jets or bright points. In contrast to that, seven events are associated
with small-scale features, which show a large variety of dynamics. Some
resemble small bright points, while others show an eruptive nature, all
of which are faint and only live for a few minutes; we cannot rule out
that several of these sources may be fainter and, hence, less obvious
jets. Since the complex structure of the solar wind is known, this
suggests that new sources have to be considered or better methods used
to analyse the known sources. This work shows that small and frequent
features, which were previously neglected, can cause strong upflows in
the solar corona. These results emphasise the importance of the first
observations from the Extreme-Ultraviolet Imager (EUI) on board Solar
Orbiter, which revealed complex small-scale coronal structures.
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Title: How Can Solar-C/SOSPIM Contribute to the Understanding of
Quasi-Periodic Pulsations in Solar Flares?
Authors: Dominique, Marie; Dolla, Laurent; Zhukov, Andrei; Alberti,
Andrea; Berghmans, David; Gissot, Samuel; Hara, Hirohisa; Harra,
Louise; Imada, Shinsuke; Koller, Silvio; Meier, Leandro; Pfiffner,
Daniel; Shimizu, Toshifumi; Tye, Daniel; Watanabe, Kyoko
2021AGUFMSH25E2124D Altcode:
Quasi-periodic pulsations (QPPs) refer to nearly-periodic oscillations
that are often observed in irradiance time series during solar flares
and have also been reported in several stellar flares. In the last
years, several statistical studies based on Soft X-ray measurements
have reached the conclusion that QPPs are present in most solar flares
of class M and above. Still, the mechanism at the origin of QPPs is
under debate. Are they caused by waves or periodic fluctuations of the
magnetic reconnection driving the flare? Analyzing the characteristics
of QPPs and their evolution during the flare could help identifying
their origin. However, QPPs sometimes exhibit very different
periodicities, and do not always happen during the same phase of the
flare. All this could point to the coexistence of QPPs with different
origin mechanism, and indicates the need for more observations. In this
context, the spectral solar irradiance monitor SOSPIM, that will be
part of the JAXA SOLAR C mission and that will complement the EUVST
spectrograph measurements, could be a valuable asset. SOSPIM will
observe the solar chromosphere and corona in the Lyman-alpha and EUV
spectral ranges at high cadence. In this presentation, we review the
current knowledge of QPPs and describe what could be the contribution
of SOSPIM to push their understanding one step forward.
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Title: Full Vector Velocity Reconstruction Using Solar Orbiter
Doppler Map Observations.
Authors: Podladchikova, Olena; Harra, Louise; Barczynski, Krzysztof;
Mandrini, Cristina; Auchere, F.; Berghmans, David; Buchlin, Eric;
Dolla, Laurent; Mierla, Marilena; Parenti, Susanna; Rodriguez, Luciano
2021AGUFMNG35B0432P Altcode:
The Solar Orbiter mission opens up opportunities forthe
combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different space spectrometerswill
be located at wide angles to each other, allowing three-dimensional
(3D) spectroscopy of the solar atmosphere.The aim of this work is to
prepare the methodology to facilitate the reconstruction of 3D vector
velocities from two stereoscopicLOS Doppler velocity measurements using
the Spectral Imaging of the Coronal Environment (SPICE) on board the
Solar Orbiter andthe near-Earth spectrometers, while widely separated in
space. We develop the methodology using the libraries designed earlier
for the STEREO mission but applied to spectroscopicdata from the Hinode
mission and the Solar Dynamics Observatory. We use well-known methods
of static and dynamic solar rotationstereoscopy and the methods of
EUV stereoscopic triangulation for optically-thin coronal EUV plasma
emissions. We develop new algorithms using analytical geometry in
space to determine the 3D velocity in coronal loops. We demonstrate
our approach with the reconstruction of 3D velocity vectors in plasma
flows along "open" and "closed"magnetic loops. This technique will be
applied first to an actual situation of two spacecraft at different
separations with spectrometers onboard (SPICE versus the Interface
Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer)
during the Solar Orbiternominal phase. We summarise how these
observations can be coordinated.
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Title: Stereoscopy of extreme UV quiet Sun brightenings observed by
Solar Orbiter/EUI
Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot,
Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester,
Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin,
Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith,
Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David;
Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca,
Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre;
Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David
2021AGUFMSH21A..03Z Altcode:
We study the three-dimensional distribution of small-scale brightening
events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun
by the EUI telescope onboard the Solar Orbiter mission. We use one of
the first commissioning data sets acquired by the HRI_EUV telescope of
EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous
SDO/AIA dataset taken in the very similar 171 A passband. The spatial
resolution of the two telescopes is sufficient to identify the campfires
in both datasets. The angular separation between the two spacecraft of
around 31.5 degrees allowed for the three-dimensional reconstruction
of the position of campfires. This is the first time that stereoscopy
was achieved for structures at such a small scale. Manual and automatic
triangulation methods were used. The height of campfires is between 1000
km and 5000 km above the photosphere, and there is a good agreement
between the results of manual and automatic methods. The internal
structure of campfires is mostly not resolved by AIA, but for a large
campfire we could triangulate a few pixels, which are all in a narrow
height range between 2500 and 4500 km. The low height of campfires
suggests that they belong to the previously unresolved fine structure
of the transition region and low corona of the quiet Sun. They are
probably apexes of small-scale dynamic loops internally heated to
coronal temperatures. This work demonstrates that high-resolution
stereoscopy of structures in the solar atmosphere has become possible.
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Title: Extreme-UV quiet Sun brightenings observed by the Solar
Orbiter/EUI
Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.;
Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.;
Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.;
Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.;
Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.;
Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.;
Inhester, B.
2021A&A...656L...4B Altcode: 2021arXiv210403382B
Context. The heating of the solar corona by small heating events
requires an increasing number of such events at progressively smaller
scales, with the bulk of the heating occurring at scales that are
currently unresolved. <BR /> Aims: The goal of this work is to study the
smallest brightening events observed in the extreme-UV quiet Sun. <BR />
Methods: We used commissioning data taken by the Extreme Ultraviolet
Imager (EUI) on board the recently launched Solar Orbiter mission. On
30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its
High Resolution EUV telescope (HRI<SUB>EUV</SUB>, 17.4 nm passband)
reached an exceptionally high two-pixel spatial resolution of 400
km. The size and duration of small-scale structures was determined
by the HRI<SUB>EUV</SUB> data, while their height was estimated
from triangulation with simultaneous images from the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory
mission. This is the first stereoscopy of small-scale brightenings
at high resolution. <BR /> Results: We observed small localised
brightenings, also known as `campfires', in a quiet Sun region with
length scales between 400 km and 4000 km and durations between 10 s and
200 s. The smallest and weakest of these HRI<SUB>EUV</SUB> brightenings
have not been previously observed. Simultaneous observations from the
EUI High-resolution Lyman-α telescope (HRI<SUB>Lya</SUB>) do not show
localised brightening events, but the locations of the HRI<SUB>EUV</SUB>
events clearly correspond to the chromospheric network. Comparisons with
simultaneous AIA images shows that most events can also be identified
in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA,
although they appear weaker and blurred. Our differential emission
measure analysis indicated coronal temperatures peaking at log T ≈
6.1 − 6.15. We determined the height for a few of these campfires to
be between 1000 and 5000 km above the photosphere. <BR /> Conclusions:
We find that `campfires' are mostly coronal in nature and rooted in the
magnetic flux concentrations of the chromospheric network. We interpret
these events as a new extension to the flare-microflare-nanoflare
family. Given their low height, the EUI `campfires' could stand as a
new element of the fine structure of the transition region-low corona,
that is, as apexes of small-scale loops that undergo internal heating
all the way up to coronal temperatures.
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Title: First observations from the SPICE EUV spectrometer on Solar
Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest,
S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.;
Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest,
C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.;
Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.;
Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.;
Chitta, L. P.
2021A&A...656A..38F Altcode: 2021arXiv211011252F
<BR /> Aims: We present first science observations taken during the
commissioning activities of the Spectral Imaging of the Coronal
Environment (SPICE) instrument on the ESA/NASA Solar Orbiter
mission. SPICE is a high-resolution imaging spectrometer operating at
extreme ultraviolet (EUV) wavelengths. In this paper we illustrate
the possible types of observations to give prospective users a
better understanding of the science capabilities of SPICE. <BR />
Methods: We have reviewed the data obtained by SPICE between April
and June 2020 and selected representative results obtained with
different slits and a range of exposure times between 5 s and 180
s. Standard instrumental corrections have been applied to the raw
data. <BR /> Results: The paper discusses the first observations
of the Sun on different targets and presents an example of the full
spectra from the quiet Sun, identifying over 40 spectral lines from
neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur,
magnesium, and iron. These lines cover the temperature range between
20 000 K and 1 million K (10 MK in flares), providing slices of the
Sun's atmosphere in narrow temperature intervals. We provide a list
of count rates for the 23 brightest spectral lines. We show examples
of raster images of the quiet Sun in several strong transition region
lines, where we have found unusually bright, compact structures in the
quiet Sun network, with extreme intensities up to 25 times greater
than the average intensity across the image. The lifetimes of these
structures can exceed 2.5 hours. We identify them as a transition
region signature of coronal bright points and compare their areas and
intensity enhancements. We also show the first above-limb measurements
with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and
far off limb measurements in the equatorial plane in Mg IX, Ne VIII,
and O VI lines. We discuss the potential to use abundance diagnostics
methods to study the variability of the elemental composition that can
be compared with in situ measurements to help confirm the magnetic
connection between the spacecraft location and the Sun's surface,
and locate the sources of the solar wind. <BR /> Conclusions: The
SPICE instrument successfully performs measurements of EUV spectra
and raster images that will make vital contributions to the scientific
success of the Solar Orbiter mission.
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Title: Stereoscopic measurements of coronal Doppler velocities
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C. H.; Auchère, F.; Berghmans, D.; Buchlin, É.; Dolla, L.; Mierla,
M.; Parenti, S.; Rodriguez, L.
2021A&A...655A..57P Altcode: 2021arXiv210802280P
Context. The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time different space spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere. <BR /> Aims: The aim of this
work is to prepare a methodology to facilitate the reconstruction
of 3D vector velocities from two stereoscopic line of sight (LOS)
Doppler velocity measurements using the Spectral Imaging of the
Coronal Environment (SPICE) on board the Solar Orbiter and the
near-Earth spectrometers, while widely separated in space. <BR />
Methods: We developed the methodology using the libraries designed
earlier for the STEREO mission, but applied to spectroscopic data
from the Hinode mission and the Solar Dynamics Observatory. We used
well-known methods of static and dynamic solar rotation stereoscopy and
the methods of extreme ultraviolet (EUV) stereoscopic triangulation
for optically thin coronal EUV plasma emissions. We developed new
algorithms using analytical geometry in space to determine the 3D
velocity in coronal loops. <BR /> Results: We demonstrate our approach
with the reconstruction of 3D velocity vectors in plasma flows along
`open' and `closed' magnetic loops. This technique will be applied
to an actual situation of two spacecraft at different separations
with spectrometers on board during the Solar Orbiter nominal phase:
SPICE versus the Interface Region Imaging Spectrograph (IRIS) and
Hinode imaging spectrometer. We summarise how these observations can
be coordinated. <P />Movies associated to Fig. 1 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140457/olm">https://www.aanda.org</A>
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Title: The Formation and Lifetime of Outflows in a Solar Active Region
Authors: Brooks, David H.; Harra, Louise; Bale, Stuart D.; Barczynski,
Krzysztof; Mandrini, Cristina; Polito, Vanessa; Warren, Harry P.
2021ApJ...917...25B Altcode: 2021arXiv210603318B
Active regions are thought to be one contributor to the slow solar
wind. Upflows in EUV coronal spectral lines are routinely observed at
their boundaries, and provide the most direct way for upflowing material
to escape into the heliosphere. The mechanisms that form and drive these
upflows, however, remain to be fully characterized. It is unclear how
quickly they form, or how long they exist during their lifetimes. They
could be initiated low in the atmosphere during magnetic flux emergence,
or as a response to processes occurring high in the corona when the
active region is fully developed. On 2019 March 31 a simple bipolar
active region (AR 12737) emerged and upflows developed on each side. We
used observations from Hinode, SDO, IRIS, and Parker Solar Probe (PSP)
to investigate the formation and development of the upflows from the
eastern side. We used the spectroscopic data to detect the upflow,
and then used the imaging data to try to trace its signature back to
earlier in the active region emergence phase. We find that the upflow
forms quickly, low down in the atmosphere, and that its initiation
appears associated with a small field-opening eruption and the onset
of a radio noise storm detected by PSP. We also confirmed that the
upflows existed for the vast majority of the time the active region
was observed. These results suggest that the contribution to the solar
wind occurs even when the region is small, and continues for most of
its lifetime.
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Title: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
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Title: Comparison of active region upflow and core properties using
simultaneous spectroscopic observations from IRIS and Hinode
Authors: Barczynski, Krzysztof; Harra, Louise; Kleint, Lucia; Panos,
Brandon; Brooks, David H.
2021A&A...651A.112B Altcode: 2021arXiv210410234B
Context. The origin of the slow solar wind is still an open issue. It
has been suggested that upflows at the edge of active regions are
a possible source of the plasma outflow and therefore contribute
to the slow solar wind. <BR /> Aims: We investigate the origin and
morphology of the upflow regions and compare the upflow region and
the active region core properties. <BR /> Methods: We studied how the
plasma properties of flux, Doppler velocity, and non-thermal velocity
change throughout the solar atmosphere, from the chromosphere via the
transition region to the corona in the upflow region and the core
of an active region. We studied limb-to-limb observations of the
active region (NOAA 12687) obtained from 14 to 25 November 2017. We
analysed spectroscopic data simultaneously obtained from IRIS and
Hinode/EIS in the six emission lines Mg II 2796.4Å, C II 1335.71Å,
Si IV 1393.76Å, Fe XII 195.12Å, Fe XIII 202.04Å, and Fe XIV
270.52Å and 274.20Å. We studied the mutual relationships between the
plasma properties for each emission line, and we compared the plasma
properties between the neighbouring formation temperature lines. To
find the most characteristic spectra, we classified the spectra in
each wavelength using the machine learning technique k-means. <BR />
Results: We find that in the upflow region the Doppler velocities of
the coronal lines are strongly correlated, but the transition region
and coronal lines show no correlation. However, their fluxes are
strongly correlated. The upflow region has a lower density and lower
temperature than the active region core. In the upflow region, the
Doppler velocity and non-thermal velocity show a strong correlation in
the coronal lines, but the correlation is not seen in the active region
core. At the boundary between the upflow region and the active region
core, the upflow region shows an increase in the coronal non-thermal
velocity, the emission obtained from the DEM, and the domination
of the redshifted regions in the chromosphere. <BR /> Conclusions:
The obtained results suggest that at least three parallel mechanisms
generate the plasma upflow: (1) The reconnection between closed loops
and open magnetic field lines in the lower corona or upper chromosphere;
(2) the reconnection between the chromospheric small-scale loops and
open magnetic field; and (3) the expansion of the magnetic field lines
that allows the chromospheric plasma to escape to the solar corona.
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Title: Vector Velocities Measurements with the Solar Orbiter SPICE
Spectrometer
Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini,
C.; Auchère, F.; Berghmans, D.; Buchlin, E.; Dolla, L.; Mierla, M.;
Parenti, S.; Rodriguez, L.
2021AAS...23831312P Altcode:
The Solar Orbiter mission, with an orbit outside the Sun-Earth
line and leaving the ecliptic plane, opens up opportunities for
the combined analysis of measurements obtained by solar imagers and
spectrometers. For the first time, different spectrometers will be
located at wide angles to each other, allowing three-dimensional (3D)
spectroscopy of the solar atmosphere. Here we develop a methodology to
prepare for this kind of analysis, by using data from the Hinode mission
and the Solar Dynamics Observatory, respectively. We employ solar
rotation to simulate measurements of spectrometers with different views
of the solar corona. The resulting data allow us to apply stereoscopic
tie-pointing and triangulation techniques designed for the STEREO
spacecraft pair, and to perform 3D analysis of the Doppler shifts of
a quasi-stationary active region. Our approach allows the accurate
reconstruction of 3D velocity vectors in plasma flows along "open" and
"closed" magnetic loops. This technique will be applied to the actual
situation of two spacecraft at different separations with spectrometers
on board (the Solar Orbiter Spectral Imaging of the Coronal Environment
versus the Interface Region Imaging Spectrograph (IRIS) and Hinode
imaging spectrometer) and we summarise how these observations can be
coordinated to assess vector velocity measurements. This 3D spectroscopy
method will facilitate the understanding of the complex flows that
take place throughout the solar atmosphere.
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Title: The active region source of a type III radio storm observed
by Parker Solar Probe during encounter 2
Authors: Harra, L.; Brooks, D. H.; Bale, S. D.; Mandrini, C. H.;
Barczynski, K.; Sharma, R.; Badman, S. T.; Vargas Domínguez, S.;
Pulupa, M.
2021A&A...650A...7H Altcode: 2021arXiv210204964H
Context. We investigated the source of a type III radio burst storm
during encounter 2 of NASA's Parker Solar Probe (PSP) mission. <BR />
Aims: It was observed that in encounter 2 of NASA's PSP mission there
was a large amount of radio activity and, in particular, a noise storm
of frequent, small type III bursts from 31 March to 6 April 2019. Our
aim is to investigate the source of these small and frequent bursts. <BR
/> Methods: In order to do this, we analysed data from the Hinode EUV
Imaging Spectrometer, PSP FIELDS, and the Solar Dynamics Observatory
Atmospheric Imaging Assembly. We studied the behaviour of active region
12737, whose emergence and evolution coincides with the timing of the
radio noise storm and determined the possible origins of the electron
beams within the active region. To do this, we probed the dynamics,
Doppler velocity, non-thermal velocity, FIP bias, and densities,
and carried out magnetic modelling. <BR /> Results: We demonstrate
that although the active region on the disc produces no significant
flares, its evolution indicates it is a source of the electron beams
causing the radio storm. They most likely originate from the area
at the edge of the active region that shows strong blue-shifted
plasma. We demonstrate that as the active region grows and expands,
the area of the blue-shifted region at the edge increases, which is
also consistent with the increasing area where large-scale or expanding
magnetic field lines from our modelling are anchored. This expansion
is most significant between 1 and 4 April 2019, coinciding with the
onset of the type III storm and the decrease of the individual burst's
peak frequency, indicating that the height at which the peak radiation
is emitted increases as the active region evolves.
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Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
2021SoPh..296...70R Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
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Title: Matching Temporal Signatures of Solar Features to Their
Corresponding Solar-Wind Outflows
Authors: de Pablos, D.; Long, D. M.; Owen, C. J.; Valori, G.; Nicolaou,
G.; Harra, L. K.
2021SoPh..296...68D Altcode: 2021arXiv210309077D
The role of small-scale coronal eruptive phenomena in the generation
and heating of the solar wind remains an open question. Here, we
investigate the role played by coronal jets in forming the solar wind
by testing whether temporal variations associated with jetting in EUV
intensity can be identified in the outflowing solar-wind plasma. This
type of comparison is challenging due to inherent differences between
remote-sensing observations of the source and in-situ observations
of the outflowing plasma, as well as travel time and evolution
of the solar wind throughout the heliosphere. To overcome these,
we propose a novel algorithm combining signal filtering, two-step
solar-wind ballistic back-mapping, window shifting, and Empirical
Mode Decomposition. We first validate the method using synthetic data,
before applying it to measurements from the Solar Dynamics Observatory
and Wind spacecraft. The algorithm enables the direct comparison of
remote-sensing observations of eruptive phenomena in the corona to
in-situ measurements of solar-wind parameters, among other potential
uses. After application to these datasets, we find several time windows
where signatures of dynamics found in the corona are embedded in
the solar-wind stream, at a time significantly earlier than expected
from simple ballistic back-mapping, with the best-performing in-situ
parameter being the solar-wind mass flux.
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Title: Upflows in the Upper Solar Atmosphere
Authors: Tian, Hui; Harra, Louise; Baker, Deborah; Brooks, David H.;
Xia, Lidong
2021SoPh..296...47T Altcode: 2021arXiv210202429T
Spectroscopic observations at extreme- and far-ultraviolet wavelengths
have revealed systematic upflows in the solar transition region and
corona. These upflows are best seen in the network structures of
the quiet Sun and coronal holes, boundaries of active regions, and
dimming regions associated with coronal mass ejections. They have been
intensively studied in the past two decades because they are likely to
be closely related to the formation of the solar wind and heating of the
upper solar atmosphere. We present an overview of the characteristics
of these upflows, introduce their possible formation mechanisms, and
discuss their potential roles in the mass and energy transport in the
solar atmosphere. Although past investigations have greatly improved
our understanding of these upflows, they have left us with several
outstanding questions and unresolved issues that should be addressed
in the future. New observations from the Solar Orbiter mission, the
Daniel K. Inouye Solar Telescope, and the Parker Solar Probe will
likely provide critical information to advance our understanding of
the generation, propagation, and energization of these upflows.
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Title: Stereoscopic Measurements of Coronal Doppler Velocities aboard
Solar Orbiter
Authors: Podladchikova, Olena; Harra, Louise K.; Mandrini, Cristina
H.; Rodriguez, Luciano; Parenti, Susanna; Dolla, Laurent; Buchlin,
Eric; Auchere, Frederic; Mierla, Marilena; Barczynski, Krzysztof
2021cosp...43E.957P Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region.We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI), the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
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Title: Coronal 'camp-fires' in the quiet Sun as observed by Solar
Orbiter EUV Imagers
Authors: Harra, Louise K.
2021cosp...43E.950H Altcode:
The quiet Sun is known to be extremely dynamic, with an array of
small-scale energy releases occurring in features such as network
and internetwork, bright points, and are observed throughout
the solar atmosphere - from the photosphere to the corona. The
Interface Region Imaging Spectrograph (IRIS) data shows UV bursts
(e.g. Young et al., 2018), that have at least an order of magnitude
enhancement in intensity, show strong flows, and are on spatial scales
of 500-1000km. These are often associated with opposite polarity
magnetic fragments that cancel, and are observed in the transition
region. Similar phenomena are seen in the optical bands called Ellerman
bombs or more recently quiet Sun Ellerman-like brightenings (QSEB, van
der Voort et al., 2016). Coronal brightenings are also readily observed
and there is significant interest in these, to understand whether
they contribute to the heating of the corona. Statistical studies
of these coronal brightenings have shown a power-law behaviour, and
this has found to be around 1.8 (e.g. Aschwanden et al., 2000). There
is a strong interesting in understanding the smaller-scale events to
determine if they can indeed heat the corona. To do this the spatial
resolution must be high. The Hi-C rocket flights have observed with
spatial resolutions of 100 km, and small-scale brightenings have been
seen at the se size scales (e.g. Winbarger et al., 2013). The EUV
Imagers (EUI) on Solar Orbiter has taken the first commissioning data
in 2020, and in this presentation, we describe the smallest features
yet seen in the EUV that have been coined 'camp-fires'. We describe
their characteristics, and discuss future observations once we're in
the true science phase of the mission at the end of 2021.
---------------------------------------------------------
Title: The Extreme ultraviolet imager onboard Solar Orbiter
Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere,
Frederic; Long, David; Schuehle, Udo; Rochus, Pierre
2021cosp...43E.949B Altcode:
The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
instrument package of the ESA/NASA Solar Orbiter mission that will
explore the inner heliosphere and observe the Sun from vantage points
close to the Sun and out of the ecliptic. With EUI we aim to improve our
understanding of the structure and dynamics of the solar atmosphere,
globally as well as at high resolution, and from high solar latitude
perspectives. The EUI consists of three telescopes, the Full Sun Imager
(FSI) and two High Resolution Imagers (HRIs), which are optimised
to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a
coverage from chromosphere up to corona. The EUI instrument design
will be reviewed, and its scientific objectives and plans will be
discussed. Early results of the EUI commissioning will be presented.
---------------------------------------------------------
Title: The creation of blue-shifted regions in an active region that
lead to the onset of a radio nise storm.
Authors: Harra, Louise K.
2021cosp...43E.958H Altcode:
On 31st March 2019, a new simple bipolar active region emerged in the NE
of the Sun. This region formed from a small bright point, and developed
through expansion. For the first time, we observe the development and
expansion of the loops with time, and with magnetic modelling see how
the region at the edge of the active region form an increasing number
of open magnetic field lines. We see the development of the region
where blue-shifts form. These blue-shifted regions are always seen at
the edges of active regions as observed by the Hinode EUV Imagining
Spectrometer (EIS), and we discuss how they are formed. Alongside these
observations, Parker Solar Probe observed a radio noise storm. We track
how the blue-shifted and the radio data increase as the active region
develops in its first few days of life. The blue-shifted regions on
the active region seems to be the source of the radio noise storm,
confirming their importance as a contributor to the solar wind.
---------------------------------------------------------
Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE
Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado,
R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra,
L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca,
L.; Thompson, W. T.; Williams, D.
2020AGUFMSH038..09Z Altcode:
Linking solar activity on the surface and in the corona to the inner
heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer
SPICE (SPectral Imaging of the Coronal Environment) will provide
relative abundance measurements which will be key in this quest
as different structures on the Sun have different abundances as a
consequence of the FIP (First Ionization Potential) effect. Solar
Orbiter's unique combination of remote sensing and in-situ instruments
coupled with observation from other missions such as Parker Solar
Probe will allow us to compare in-situ and remote sensing composition
data. With the addition of modeling, these new results will allow us
to trace back the source of heliospheric plasma. As high telemetry
will not always be available with SPICE, we have developed a method
for measuring relative abundances that is both telemetry efficient
and reliable. Unlike methods based on Differential Emission Measure
(DEM) inversion, the Linear Combination Ratio (LCR) method does not
require a large number of spectral lines. This new method is based
on linear combinations of UV spectral lines. The coefficients of
the combinations are optimized such that the ratio of two linear
combinations of radiances would yield the relative abundance of two
elements. We present some abundance diagnostics tested on different
combinations of spectral lines observable by SPICE.
---------------------------------------------------------
Title: Dynamics and thermal structure in the quiet Sun seen by SPICE
Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.;
Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.;
Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams,
D.; Young, P. R.
2020AGUFMSH038..03P Altcode:
We will present some of the early data of the Spectral Imaging of the
Coronal Environment (SPICE) instrument on Solar Orbiter. One of the
unique features of SPICE is its capability to record a wide range of
wavelengths in the extreme UV with the possibility to record spectral
lines giving access to a continuous plasma temperature range from 10.000
K to well above 1 MK. The data taken so far were for commissioning
purposes and they can be used for a preliminary evaluation of the
science performance of the instrument. Here we will concentrate on
sample spectra covering the whole wavelength region and on the early
raster maps acquired in bright lines in the quiet Sun close to disk
center. Looking at different quiet Sun features we investigate the
thermal structure of the atmosphere and flow structures. For this
we apply fits to the spectral profiles and check the performance in
terms of Doppler shifts and line widths to retrieve the structure of
the network in terms of dynamics. While the amount of data available
so far is limited, we will have a first look on how quiet Sun plasma
responds to heating events. For this, we will compare spectral lines
forming at different temperatures recorded at strictly the same time.
---------------------------------------------------------
Title: A Journey of Exploration to the Polar Regions of a Star:
Probing the Solar Poles and the Heliosphere from High Helio-Latitude
Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.;
Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.;
Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi,
S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.;
Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.;
Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli,
M.; Sekii, T.; Spadaro, D.; Veronig, A.
2020AGUFMSH0110005F Altcode:
A mission to view the solar poles from high helio-latitudes (above
60°) will build on the experience of Solar Orbiter as well as a long
heritage of successful solar missions and instrumentation (e.g. SOHO,
STEREO, Hinode, SDO), but will focus for the first time on the solar
poles, enabling scientific investigations that cannot be done by
any other mission. One of the major mysteries of the Sun is the solar
cycle. The activity cycle of the Sun drives the structure and behaviour
of the heliosphere and is, of course, the driver of space weather. In
addition, solar activity and variability provides fluctuating input
into the Earth climate models, and these same physical processes
are applicable to stellar systems hosting exoplanets. One of the
main obstructions to understanding the solar cycle, and hence all
solar activity, is our current lack of understanding of the polar
regions. We describe a mission concept that aims to address this
fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.
---------------------------------------------------------
Title: A Comparison of the Active Region Upflow and Core Morphologies
Using Simultaneous Spectroscopic Observations from IRIS and Hinode.
Authors: Barczynski, K.; Harra, L. K.; Kleint, L.; Panos, B.
2020AGUFMSH004..05B Altcode:
The origin of the slow solar wind is still an open issue. It has
been suggested that upflows at the edge of the active region are the
source of the plasma outflow, and therefore contribute to the slow
solar wind . However, the origin and morphology of the upflow region
remain open questions. We investigated how the plasma properties
(flux, Doppler velocity, and non-thermal velocity) change throughout
the solar atmosphere, from the chromosphere via the transition
region to the corona. We compared the upflow region and the core of
an active region. We studied limb-to-limb observation of the active
region (NOAA 12687) obtained between 14th and 25th November 2017. We
analyzed spectroscopic data simultaneously obtained from Hinode/EIS
and IRIS in six wavelengths (MgII, CII, SiIV, FeXII, FeXIII, and
FeXIV). After the high-precision alignment (accuracy of the Hinode
pixel size) of the raster maps, we studied the mutual relation between
the plasma properties for each line, as well as compared the plasma
properties in the close formation temperature lines. To find the most
characteristic spectra, we classified the spectra in each wavelength
using the machine learning technique k-means . We found that the
fluxes of the lines formed in the close temperatures are highly
correlated in the chromosphere via transition region to the corona. In
the corona, the Doppler velocities are well correlated too. Despite
high-correlation between the transition region and coronal fluxes,
the Doppler velocities are independent in our active region. In
coronal lines, the average non-thermal velocity is higher in the
upflow region than the active region core. In the transition region,
the velocities are similar; thus the non-thermal motions are essential
in the coronal upflow. We found several mutual relations between the
plasma parameters in different spectral lines. These relations and
the spectra classification results suggest that the plasma upflow
begins in the solar corona, but the nature of the upflow region can
be determined from the underlying layers.
---------------------------------------------------------
Title: Analysis of time-domain correlations between EUV and in-situ
observations of coronal jets
Authors: de Pablos, D.; Owen, C. J.; Long, D.; Harra, L. K.; Valori,
G.; Nicolaou, G.
2020AGUFMSH0290018D Altcode:
The role of small-scale coronal eruptive phenomena in the origin and
heating of the solar wind remains an open question. In this work we
attempt to determine the role played by coronal jets in forming the
solar wind. This is a challenging problem due to inherent differences
between remote-sensing observations of the source and in-situ
observations of the outflowing plasma, as well as its travel time and
evolution throughout the heliosphere. To overcome these challenges,
we propose the use of Empirical Mode Decomposition to enable direct
comparison of temporal signatures within remote sensing observations of
eruptive phenomena in the corona and in-situ measurements of the solar
wind. The technique is first validated using artificial data before
being applied to measurements from the Solar Dynamics Observatory and
Wind spacecraft. We discuss the potential reasons for discrepancies
between results from the artificial data and observations at 1 AU,
and their implications on the solar wind nature.
---------------------------------------------------------
Title: Observation of Smallest Ever Detected Brightening Events with
the Solar Orbiter EUI HRI-EUV Imager
Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere,
F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado,
R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
2020AGUFMSH038..01P Altcode:
The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter
acquired its first images in May 2020. The passband of the 17.4 nm
High Resolution Imager (HRI-EUV) is dominated by emission lines of
Fe IX and Fe X, that is the 1 million degree solar corona. The solar
atmosphere at this temperature is dynamic at all scales, down to the
highest spatial resolution available from instruments priori to Solar
Orbiter. During the Commissioning phase, HRI-EUV acquired several high
temporal resolution (a few seconds) sequences at quiet Sun regions at
disk center. The instrument revealed a multitude of brightenings at
the smallest-ever detectable spatial scales which, at that time, was
about 400 km (two pixels). These events appear to be present everywhere
all the time. We present the first results of the analysis of these
sequences with the aim of understanding the role of these small scale
events in the heating of the solar corona.
---------------------------------------------------------
Title: Stereoscopic Measurements of Coronal Doppler Velocities
Authors: Podladchikova, O.; Harra, L. K.; Barczynski, K.; Mandrini,
C. H.; Auchere, F.; Buchlin, E.; Dolla, L.; Mierla, M.; Rodriguez, L.
2020AGUFMSH038..07P Altcode:
The Solar Orbiter mission, whose orbit is outside the Sun-Earth
line, opens up novel opportunities for the combined analysis of
measurements by solar imagers and spectrometers. For the first time
different spectrometers will be located at wide angles with each
other allowing 3D spectroscopy in the solar atmosphere. In order
to develop a methodology for these opportunities we make use of the
Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) and by employing solar
rotation we simulate the measurements of two spectrometers that have
different views of solar corona. The resulting data allows us to apply
stereoscopic tie-pointing and triangulation techniques designed for
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation)
imaging suite on the STEREO (Solar Terrestrial Relations Observatory)
spacecraft pair and perform three-dimensional analysis of Doppler shifts
of quasi-stationary active region. We present a technique that allows
the accurate reconstruction of the 3D velocity vector in plasma flows
along open and closed magnetic loops. This technique will be applied
to the real situation of two spacecraft at different separations with
spectrometers onboard. This will include the Solar Orbiter Spectral
Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme
Ultraviolet Imager (EUI),the Interface Region Imaging Spectrograph
(IRIS) and Hinode EIS spectrometers and we summarise how these can be
coordinated. This 3D spectroscopy is a new research domain that will
aid the understanding of the complex flows that take place throughout
the solar atmosphere.
---------------------------------------------------------
Title: Constraining Global Coronal Models with Multiple Independent
Observables
Authors: Badman, S. T.; Brooks, D.; Petrie, G. J. D.; Poirier, N.;
Warren, H.; Bale, S. D.; de Pablos, D.; Harra, L.; Rouillard, A. P.;
Panasenco, O.; Velli, M. C. M.
2020AGUFMSH032..08B Altcode:
Global coronal models seek to produce an accurate physical
representation of the Sun's atmosphere which can be used to probe
the dominant plasma physics processes, to connect remote and in situ
observations and operationally to predict space weather events which
can impact the Earth. Assessing their accuracy and usefulness is a
complex task and there are multiple observational pathways to provide
constraints on such models and tune their input parameters. In this
work, we aim to combine several such independent constraints in
a systematic fashion on coronal models. We study the intervals of
Parker Solar Probe's early solar encounters to leverage the unique in
situ observations taken close to the Sun, and the wealth of supporting
observations and prior work analyzing these time intervals. We require
our coronal models to predict the distribution of coronal holes on
the solar surface, and the neutral line topology. We compare these
predictions to (1) direct Extreme Ultraviolet (EUV) observations
of coronal hole locations, (2) white light Carrington maps of the
probable neutral line location at a few solar radii, (3) the magnetic
sector structure measured in situ by Parker Solar Probe as well as
1AU assets. For each of these constraints we compute a simple metric
to evaluate model agreement and compare and contrast these metrics
to evaluate and rank the overall accuracy of the models over a range
of input parameters. Initial results using the coronal hole metric
to analyze Potential Field Source Surface (PFSS) models indicate the
optimum source surface height (Rss) parameter varied from encounter to
encounter. Rss = 1.5 - 2.0 R_sun is shown to work best for Encounters
1 and 3, but higher (2.0-2.5 R_sun) for encounter 2, in agreement with
the magnetic sector structure metric and previous work (e.g. Panasenco
et al. 2020). We discuss the extension of these results to all three
metrics, assess differences in model accuracy among input photospheric
boundary conditions and investigate models with more physics than PFSS.
---------------------------------------------------------
Title: First Results From SPICE EUV Spectrometer on Solar Orbiter
Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest,
S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.;
Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik,
T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller,
D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson,
W. T.; Tustain, S.; Williams, D.; Young, P. R.
2020AGUFMSH038..02F Altcode:
SPICE (Spectral Imaging of Coronal Environment) is one of the remote
sensing instruments onboard Solar Orbiter. It is an EUV imaging
spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm
and 96.6-105.1 nm. SPICE is capable of recording full spectra in these
bands with exposures as short as 1s. SPICE is the only Solar Orbiter
instrument that can measure EUV spectra from the disk and low corona
of the Sun and record all spectral lines simultaneously. SPICE uses
one of three narrow slits, 2"x11', 4”x11', 6”x11', or a wide slit
30”x14'. The primary mirror can be scanned in a direction perpendicular
to the slit, allowing raster images of up to 16' in size. <P />We
present an overview of the first SPICE data taken on several days
during the instrument commissioning carried out by the RAL Space team
between 2020 April 21 and 2020 June 14. We also include results from
SPICE observations at the first Solar Orbiter perihelion at 0.52AU,
taken between June 16-21<SUP>st</SUP>. We give examples of full spectra
from the quiet Sun near disk centre and provide a list of key spectral
lines emitted in a range of temperatures between 10,000 K and over 1
million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen,
neon, sulphur and magnesium. We show examples of first raster images
in several strong lines, obtained with different slits and a range
of exposure times between 5s and 180s. We describe the temperature
coverage and density diagnostics, determination of plasma flows, and
discuss possible applications to studies of the elemental abundances
in the corona. We also show the first off-limb measurements with SPICE,
as obtained when the spacecraft pointed at the limb.
---------------------------------------------------------
Title: The Solar-C (EUVST) mission: the latest status
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko; Suematsu,
Yoshinori; Hara, Hirohisa; Tsuzuki, Toshihiro; Katsukawa, Yukio; Kubo,
Masahito; Ishikawa, Ryoko; Watanabe, Tetsuya; Toriumi, Shin; Ichimoto,
Kiyoshi; Nagata, Shin'ichi; Hasegawa, Takahiro; Yokoyama, Takaaki;
Watanabe, Kyoko; Tsuno, Katsuhiko; Korendyke, Clarence M.; Warren,
Harry; De Pontieu, Bart; Boerner, Paul; Solanki, Sami K.; Teriaca,
Luca; Schuehle, Udo; Matthews, Sarah; Long, David; Thomas, William;
Hancock, Barry; Reid, Hamish; Fludra, Andrzej; Auchère, Frederic;
Andretta, Vincenzo; Naletto, Giampiero; Poletto, Luca; Harra, Louise
2020SPIE11444E..0NS Altcode:
Solar-C (EUVST) is the next Japanese solar physics mission to
be developed with significant contributions from US and European
countries. The mission carries an EUV imaging spectrometer with
slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic
Telescope) as the mission payload, to take a fundamental step towards
answering how the plasma universe is created and evolves and how the
Sun influences the Earth and other planets in our solar system. In
April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA
(Japan Aerospace Exploration Agency) has made the final down-selection
for this mission as the 4th in the series of competitively chosen
M-class mission to be launched with an Epsilon launch vehicle in mid
2020s. NASA (National Aeronautics and Space Administration) has selected
this mission concept for Phase A concept study in September 2019 and
is in the process leading to final selection. For European countries,
the team has (or is in the process of confirming) confirmed endorsement
for hardware contributions to the EUVST from the national agencies. A
recent update to the mission instrumentation is to add a UV spectral
irradiance monitor capability for EUVST calibration and scientific
purpose. This presentation provides the latest status of the mission
with an overall description of the mission concept emphasizing on key
roles of the mission in heliophysics research from mid 2020s.
---------------------------------------------------------
Title: Dynamics and Flows in Active Region NOAA12737 that can
contribute to Type III Bursts observed by Parker Solar Probe during
Encounter 2.
Authors: Harra, L.; Brooks, D.; Barczynski, K.; Mandrini, C. H.;
Vargas-Dominguez, S.; Bale, S.; Badman, S. T.; Raouafi, N. E.;
Rouillard, A. P.
2020AGUFMSH0240001H Altcode:
We have analysed solar activity on the Sun during encounter 2 of the
Parker Solar Probe mission. We studied the period from 30<SUP>th</SUP>
March to 4<SUP>th</SUP> April when a small active region (NOAA 12737)
emerged. This active region showed no significant flaring. During this
time period there were however, an increasing number of type III bursts
measured by the FIELDS instrument. We analyse solar data from SDO-AIA,
SDO-HMI and Hinode EIS to determine what the potential sources of
the type III bursts could be, which occur on timescales of tens of
seconds. The active region core shows small brightenings in EUV and
X-ray wavebands, but these are not continuous, and seem unlikely to be
connected. There are magnetic field changes due to the active region
emergence, which occur on timescales of hours rather than seconds. There
are small scale magnetic flux emergences but these are not frequent
enough to be linked to the continuous type III bursts. As the active
region emerges, we track the upflows at the edge of the active region
as they are created and evolve. We show evidence of variations in the
upflows that seem to be the most likely candidates for the sources of
the type III bursts.
---------------------------------------------------------
Title: Current Status of the Solar-C_EUVST Mission
Authors: Imada, S.; Shimizu, T.; Kawate, T.; Toriumi, S.; Katsukawa,
Y.; Kubo, M.; Hara, H.; Suematsu, Y.; Ichimoto, K.; Watanabe, T.;
Watanabe, K.; Yokoyama, T.; Warren, H.; Long, D.; Harra, L. K.;
Teriaca, L.
2020AGUFMSH056..05I Altcode:
Solar-C_EUVST (EUV High-Throughput Spectroscopic Telescope) is designed
to comprehensively understand the energy and mass transfer from the
solar surface to the solar corona and interplanetary space, and to
investigate the elementary processes that take place universally
in cosmic plasmas. As a fundamental step towards answering how the
plasma universe is created and evolves, and how the Sun influences
the Earth and other planets in our solar system, the proposed mission
is designed to comprehensively understand how mass and energy are
transferred throughout the solar atmosphere. Understanding the solar
atmosphere, which connects to the heliosphere via radiation, the solar
wind and coronal mass ejections, and energetic particles is pivotal
for establishing the conditions for life and habitability in the solar
system. <P />The two primary science objectives for Solar-C_EUVST are :
I) Understand how fundamental processes lead to the formation of the
solar atmosphere and the solar wind, II) Understand how the solar
atmosphere becomes unstable, releasing the energy that drives solar
flares and eruptions. Solar-C_EUVST will, A) seamlessly observe all
the temperature regimes of the solar atmosphere from the chromosphere
to the corona at the same time, B) resolve elemental structures of the
solar atmosphere with high spatial resolution and cadence to track their
evolution, and C) obtain spectroscopic information on the dynamics of
elementary processes taking place in the solar atmosphere. <P />In this
talk, we will first discuss the science target of the Solar-C_EUVST,
and then discuss the current status of the Solar-C_EUVST mission.
---------------------------------------------------------
Title: Calibrating optical distortions in the Solar Orbiter SPICE
spectrograph
Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.;
Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.;
Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.;
Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.;
Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams,
D.; Sidher, S.
2020AGUFMSH0360029T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument on
Solar Orbiter is a high-resolution imaging spectrometer operating
at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and
97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar
image onto the entrance slit of the spectrometer section. A Toroidal
Variable Line Space (TVLS) grating images the entrance slit onto a
pair of MCP-intensified APS detectors. Ray-tracing analysis prior
to launch showed that the instrument was subject to a number of
small image distortions which need to be corrected in the final data
product. We compare the ray tracing results with measurements made in
flight. Co-alignment with other telescopes on Solar Orbiter will also
be examined.
---------------------------------------------------------
Title: First results from the EUI and SPICE observations of Alpha
Leo near Solar Orbiter first perihelion
Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta,
V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.;
Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar
Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.;
Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.;
Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360024B Altcode:
On June 16th 2020 Solar Orbiter made a dedicated observing campaign
where the spacecraft pointed to the solar limb to allow some of the
high resolution instruments to observe the ingress (at the east limb)
and later the egress (west limb) of the occultation of the star Alpha
Leonis by the solar disk. The star was chosen because its luminosity and
early spectral type ensure high and stable flux at wavelengths between
100 and 122 nanometers, a range observed by the High Resolution EUI
Lyman alpha telescope (HRI-LYA) and by the long wavelength channel
of the SPICE spectrograph. Star observations, when feasible, allow
to gather a great deal of information on the instrument performances,
such as the radiometric performance and the instrument optical point
spread function (PSF). <P />We report here the first results from the
above campaign for the two instruments.
---------------------------------------------------------
Title: Probing Upflowing Plasma in Solar Coronal Holes to Categorise
the most frequent Events
Authors: Schwanitz, C.; Harra, L.
2020AGUFMSH0110002S Altcode:
Coronal holes have many dynamic events in them, such as jets, plumes,
and small filament eruptions. In addition, a class of jets has been
observed [Young P., 2015] that are only visible in line-of-sight Doppler
velocity measurements and tend to appear in the vicinity of coronal
holes. In this work solar polar blue-shifted regions are explored and
their sources classified. Doppler velocity maps are derived from the
Fe XII 195.2Å emission line in Hinode/EIS measurements and analysed in
combination with imaging data from SDO/AIA and SDO/XRT to characterise
the regions of upflowing plasma. Of the analysed blue-shift events,
some could be explained by weak standard jets, while other events
are connected to small flaring bright points. Some blue-shift events
do not leave any significant trace in the imaging instruments. Their
contribution to the solar wind is unknown yet, however recent findings
from Parker Solar Probe data show that there are frequent small-scale
dynamics in the wind, even during quiet times [Bale S.D., Badman S.T.,
Bonnell J.W. et al., 2019]. These findings emphasise the importance
of understanding all upflowing plasma events in coronal holes. Finally
future Solar Orbiter observations of polar coronal holes, particularly
during the out of ecliptic phase, are discussed.
---------------------------------------------------------
Title: Solar Orbiter: connecting remote sensing and in situ
measurements
Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.;
Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra,
L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.;
Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter,
H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.;
Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis,
Y.; Laker, R.
2020AGUFMSH038..10H Altcode:
A key science goal of the Solar Orbiter mission is to make connections
between phenomena on the Sun and their manifestations in interplanetary
space. To that end, the spacecraft carries a carefully tailored
payload of six remote sensing instruments and four making in situ
measurements. During June 2020, while the spacecraft was around 0.5
AU from the Sun, the remote sensing instruments operated for several
days. While this was primarily an engineering activity, the resulting
observations provided outstanding measurements and represent the ideal
first opportunity to investigate the potential for making connections
between the remote sensing and in situ payloads on Solar Orbiter. <P
/>We present a preliminary analysis of the available remote sensing and
in situ observations, showing how connections can be made, and discuss
the potential for further, more precise mapping to be performed as
the mission progresses.
---------------------------------------------------------
Title: First Images and Initial In-Flight Performance of the Extreme
Ultraviolet Imager On-Board Solar Orbiter.
Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra,
L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.;
Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C.
2020AGUFMSH0360025A Altcode:
The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is
composed of two High Resolution Imagers working at 121.6 (HRI-LYA,
H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one
dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition
region) and 17.4 nm (Fe IX/X, corona). During the commissioning period
following the launch of Solar Orbiter and two and a half months of
outgassing, EUI acquired its first solar images on May 12th, 2020 at
about 0.67 AU. Most of the capabilities of the instrument have been
tested during the following weeks, which revealed excellent overall
performance. HRI-EUV already provided images with an angular resolution
equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide
images of the Sun at Lyman alpha, which have been otherwise relatively
rare, with sub-second cadence capability. FSI will provide context for
connection science but it will also explore regions of the corona never
imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI
uses a complex on-board image processing system including advanced
image compression and event detection algorithms. In particular,
commissioning tests confirm the good performance of the compression,
which is critical given the limited total telemetry volume imposed by
the mission profile. In this paper, we present the main characteristics
of the first images taken in each channel and we provide an initial
assessment of the in-flight performance.
---------------------------------------------------------
Title: First results from combined EUI and SPICE observations of
Lyman lines of Hydrogen and He II
Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.;
Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.;
Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus,
P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest,
C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp,
E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.;
Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R.
2020AGUFMSH0360003T Altcode:
The Solar Orbiter spacecraft carries a powerful set of remote
sensing instruments that allow studying the solar atmosphere with
unprecedented diagnostic capabilities. Many such diagnostics require
the simultaneous usage of more than one instrument. One example of that
is the capability, for the first time, to obtain (near) simultaneous
spatially resolved observations of the emission from the first three
lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact,
the SPectral Imaging of the Coronal Environment (SPICE) spectrometer
can observe the Lyman beta and gamma lines in its long wavelength
(SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope
of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in
the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take
images dominated by the Lyman alpha line of ionized Helium at 30.4 nm
(FSI-304). Being hydrogen and helium the main components of our star,
these very bright transitions play an important role in the energy
budget of the outer atmosphere via radiative losses and the measurement
of their profiles and radiance ratios is a fundamental constraint to
any comprehensive modelization effort of the upper solar chromosphere
and transition region. Additionally, monitoring their average ratios
can serve as a check out for the relative radiometric performance of
the two instruments throughout the mission. Although the engineering
data acquired so far are far from ideal in terms of time simultaneity
(often only within about 1 h) and line coverage (often only Lyman beta
was acquired by SPICE and not always near simultaneous images from all
three telescopes are available) the analysis we present here still
offers a great opportunity to have a first look at the potential of
this diagnostic from the two instruments. In fact, we have identified
a series of datasets obtained at disk center and at various positions
at the solar limb that allow studying the Lyman alpha to beta radiance
ratio and their relation to He II 30.4 as a function of the position
on the Sun (disk center versus limb and quiet Sun versus coronal holes).
---------------------------------------------------------
Title: Very high-resolution observations of the solar atmosphere
in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard
Solar Orbiter
Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot,
S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.;
Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C.
2020AGUFMSH0360026A Altcode:
The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of
three telescopes, the Full Sun Imager (FSI) and two High Resolution
Imagers (HRIs). The two HRI telescopes provide images of the base
of the corona, near to the chromosphere, and of the 1 million K
corona. In fact, the HRI-EUV telescope operates around 17.4 nm to
obtain images dominated by emission from lines generated from Fe-IX
and X ions, formed at about 1 MK, while the HRI-LYA telescope provides
narrow band images dominated by the H I Lyman alpha line at 121.6 nm,
formed in the upper chromosphere/lower transition region of the solar
atmosphere around 20,000 K. Thus, the two imagers provide a powerful
diagnostics of the solar structural organization, in terms of loop
hierarchies and connectivity. Here we present an analysis of the first
two near-simultaneous (within 15s) high-resolution images of the solar
quiet atmosphere obtained near disk center by the two high-resolution
telescopes on May 30th 2020, during the commissioning phase of the
mission , when Solar Orbiter was at about 0.56 AU from the Sun.
---------------------------------------------------------
Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
2020A&A...642A...6A Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements. <BR /> Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together. <BR /> Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis. <BR /> Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.
---------------------------------------------------------
Title: The Solar Orbiter Science Activity Plan. Translating solar
and heliospheric physics questions into action
Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.;
Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra,
A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.;
Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.;
Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.;
Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.;
Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.;
Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio,
L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun,
A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso,
F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.;
Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.;
Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.;
van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi,
L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine,
D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot,
S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham,
G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler,
D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier,
K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins,
J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis,
I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.;
Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis,
G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.;
Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.;
Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis,
K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien,
H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.;
Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.;
Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines,
J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.;
Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.;
Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.;
Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.;
Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.;
Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula,
G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio,
A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.;
Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann,
T.; Young, P. R.; Zhukov, A. N.
2020A&A...642A...3Z Altcode: 2020arXiv200910772Z
Solar Orbiter is the first space mission observing the solar plasma
both in situ and remotely, from a close distance, in and out of the
ecliptic. The ultimate goal is to understand how the Sun produces
and controls the heliosphere, filling the Solar System and driving
the planetary environments. With six remote-sensing and four in-situ
instrument suites, the coordination and planning of the operations are
essential to address the following four top-level science questions:
(1) What drives the solar wind and where does the coronal magnetic field
originate?; (2) How do solar transients drive heliospheric variability?;
(3) How do solar eruptions produce energetic particle radiation that
fills the heliosphere?; (4) How does the solar dynamo work and drive
connections between the Sun and the heliosphere? Maximising the
mission's science return requires considering the characteristics
of each orbit, including the relative position of the spacecraft
to Earth (affecting downlink rates), trajectory events (such
as gravitational assist manoeuvres), and the phase of the solar
activity cycle. Furthermore, since each orbit's science telemetry
will be downloaded over the course of the following orbit, science
operations must be planned at mission level, rather than at the level
of individual orbits. It is important to explore the way in which those
science questions are translated into an actual plan of observations
that fits into the mission, thus ensuring that no opportunities are
missed. First, the overarching goals are broken down into specific,
answerable questions along with the required observations and the
so-called Science Activity Plan (SAP) is developed to achieve this. The
SAP groups objectives that require similar observations into Solar
Orbiter Observing Plans, resulting in a strategic, top-level view of
the optimal opportunities for science observations during the mission
lifetime. This allows for all four mission goals to be addressed. In
this paper, we introduce Solar Orbiter's SAP through a series of
examples and the strategy being followed.
---------------------------------------------------------
Title: Observations of the Solar Corona from Space
Authors: Antonucci, Ester; Harra, Louise; Susino, Roberto; Telloni,
Daniele
2020SSRv..216..117A Altcode:
Space observations of the atmosphere of the Sun, obtained in half a
century of dedicated space missions, provide a well established picture
of the medium and large-scale solar corona, which is highly variable
with the level of solar activity through a solar cycle and evolves
with the long-term evolution of the magnetic cycles. In this review,
we summarize the physical properties and dynamics of the medium and
large-scale corona, consisting primarily of active regions, streamers
and coronal holes; describe the dependence of coronal patterns on
the magnetic field patterns changing through the solar cycle and the
properties of the regions of open magnetic flux channeling the solar
wind; the ubiquitous presence of fluctuations in the outer corona; the
rotational properties of the large-scale corona; and the persistent
hemispheric asymmetries in the emergence of magnetic fields and the
distribution of the coronal emission.
---------------------------------------------------------
Title: Understanding the origins of the heliosphere: integrating
observations and measurements from Parker Solar Probe, Solar Orbiter,
and other space- and ground-based observatories
Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron,
N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.;
St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; Auchère, F.;
Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker,
S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli,
M.; Solanki, S. K.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper,
J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.;
De Groof, A.; Williams, D.
2020A&A...642A...4V Altcode:
Context. The launch of Parker Solar Probe (PSP) in 2018, followed
by Solar Orbiter (SO) in February 2020, has opened a new window in
the exploration of solar magnetic activity and the origin of the
heliosphere. These missions, together with other space observatories
dedicated to solar observations, such as the Solar Dynamics Observatory,
Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations
from WIND and ACE, and ground based multi-wavelength observations
including the DKIST observatory that has just seen first light,
promise to revolutionize our understanding of the solar atmosphere
and of solar activity, from the generation and emergence of the Sun's
magnetic field to the creation of the solar wind and the acceleration of
solar energetic particles. <BR /> Aims: Here we describe the scientific
objectives of the PSP and SO missions, and highlight the potential for
discovery arising from synergistic observations. Here we put particular
emphasis on how the combined remote sensing and in situ observations of
SO, that bracket the outer coronal and inner heliospheric observations
by PSP, may provide a reconstruction of the solar wind and magnetic
field expansion from the Sun out to beyond the orbit of Mercury in the
first phases of the mission. In the later, out-of-ecliptic portions of
the SO mission, the solar surface magnetic field measurements from SO
and the multi-point white-light observations from both PSP and SO will
shed light on the dynamic, intermittent solar wind escaping from helmet
streamers, pseudo-streamers, and the confined coronal plasma, and on
solar energetic particle transport. <BR /> Methods: Joint measurements
during PSP-SO alignments, and magnetic connections along the same
flux tube complemented by alignments with Earth, dual PSP-Earth,
and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will
allow a better understanding of the in situ evolution of solar-wind
plasma flows and the full three-dimensional distribution of the
solar wind from a purely observational point of view. Spectroscopic
observations of the corona, and optical and radio observations,
combined with direct in situ observations of the accelerating solar
wind will provide a new foundation for understanding the fundamental
physical processes leading to the energy transformations from solar
photospheric flows and magnetic fields into the hot coronal plasma
and magnetic fields and finally into the bulk kinetic energy of the
solar wind and solar energetic particles. <BR /> Results: We discuss
the initial PSP observations, which already provide a compelling
rationale for new measurement campaigns by SO, along with ground-
and space-based assets within the synergistic context described above.
---------------------------------------------------------
Title: The Solar Orbiter mission. Science overview
Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.;
Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.;
Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic,
M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.;
Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.;
Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.;
Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.;
Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D.
2020A&A...642A...1M Altcode: 2020arXiv200900861M
<BR /> Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision
2015-2025 programme and a mission of international collaboration between
ESA and NASA, will explore the Sun and heliosphere from close up and
out of the ecliptic plane. It was launched on 10 February 2020 04:03
UTC from Cape Canaveral and aims to address key questions of solar and
heliospheric physics pertaining to how the Sun creates and controls
the Heliosphere, and why solar activity changes with time. To answer
these, the mission carries six remote-sensing instruments to observe
the Sun and the solar corona, and four in-situ instruments to measure
the solar wind, energetic particles, and electromagnetic fields. In
this paper, we describe the science objectives of the mission, and how
these will be addressed by the joint observations of the instruments
onboard. <BR /> Methods: The paper first summarises the mission-level
science objectives, followed by an overview of the spacecraft and
payload. We report the observables and performance figures of each
instrument, as well as the trajectory design. This is followed by a
summary of the science operations concept. The paper concludes with a
more detailed description of the science objectives. <BR /> Results:
Solar Orbiter will combine in-situ measurements in the heliosphere
with high-resolution remote-sensing observations of the Sun to address
fundamental questions of solar and heliospheric physics. The performance
of the Solar Orbiter payload meets the requirements derived from the
mission's science objectives. Its science return will be augmented
further by coordinated observations with other space missions and
ground-based observatories. <P />ARRAY(0x207ce98)
---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
2020A&A...642A...8R Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere. <BR /> Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives. <BR />
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor. <BR /> Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products. <BR /> Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
---------------------------------------------------------
Title: The Solaris Solar Polar Mission
Authors: Hassler, Donald M.; Newmark, Jeff; Gibson, Sarah; Harra,
Louise; Appourchaux, Thierry; Auchere, Frederic; Berghmans, David;
Colaninno, Robin; Fineschi, Silvano; Gizon, Laurent; Gosain, Sanjay;
Hoeksema, Todd; Kintziger, Christian; Linker, John; Rochus, Pierre;
Schou, Jesper; Viall, Nicholeen; West, Matt; Woods, Tom; Wuelser,
Jean-Pierre
2020EGUGA..2217703H Altcode:
The solar poles are one of the last unexplored regions of the solar
system. Although Ulysses flew over the poles in the 1990s, it did
not have remote sensing instruments onboard to probe the Sun's polar
magnetic field or surface/sub-surface flows.We will discuss Solaris,
a proposed Solar Polar MIDEX mission to revolutionize our understanding
of the Sun by addressing fundamental questions that can only be answered
from a polar vantage point. Solaris uses a Jupiter gravity assist to
escape the ecliptic plane and fly over both poles of the Sun to >75
deg. inclination, obtaining the first high-latitude, multi-month-long,
continuous remote-sensing solar observations. Solaris will address key
outstanding, breakthrough problems in solar physics and fill holes in
our scientific understanding that will not be addressed by current
missions.With focused science and a simple, elegant mission design,
Solaris will also provide enabling observations for space weather
research (e.g. polar view of CMEs), and stimulate future research
through new unanticipated discoveries.
---------------------------------------------------------
Title: Earth Energy Imbalance
Authors: Finsterle, W.; Haberreiter, M.; Harra, L.
2020LPICo2241.5126F Altcode:
We will present requirement studies regarding accuracy and precision
to successfully measure the Earth's outgoing radiation from the lunar
south polar area and discuss the technical challenges to achieve this
with an absolute radiometer.
---------------------------------------------------------
Title: Solar physics in the 2020s: DKIST, parker solar probe, and
solar orbiter as a multi-messenger constellation
Authors: Martinez Pillet, V.; Tritschler, A.; Harra, L.; Andretta, V.;
Vourlidas, A.; Raouafi, N.; Alterman, B. L.; Bellot Rubio, L.; Cauzzi,
G.; Cranmer, S. R.; Gibson, S.; Habbal, S.; Ko, Y. K.; Lepri, S. T.;
Linker, J.; Malaspina, D. M.; Matthews, S.; Parenti, S.; Petrie, G.;
Spadaro, D.; Ugarte-Urra, I.; Warren, H.; Winslow, R.
2020arXiv200408632M Altcode:
The National Science Foundation (NSF) Daniel K. Inouye Solar Telescope
(DKIST) is about to start operations at the summit of Haleakala
(Hawaii). DKIST will join the early science phases of the NASA
and ESA Parker Solar Probe and Solar Orbiter encounter missions. By
combining in-situ measurements of the near-sun plasma environment and
detail remote observations of multiple layers of the Sun, the three
observatories form an unprecedented multi-messenger constellation to
study the magnetic connectivity inside the solar system. This white
paper outlines the synergistic science that this multi-messenger
suite enables.
---------------------------------------------------------
Title: Serial Flaring in an Active Region: Exploring Why Only One
Flare Is Eruptive
Authors: Woods, Magnus M.; Inoue, Satoshi; Harra, Louise K.; Matthews,
Sarah A.; Kusano, Kanya
2020ApJ...890...84W Altcode:
Over a four hour period between 2014 June 12-13 a series of three flares
were observed within AR 12087. This sequence of flares started with a
non-eruptive M-class flare, followed by a non-eruptive C-class flare,
and finally ended with a second C-class flare that had an associated
filament eruption. In this paper we combine spectroscopic analysis of
Interface Region Imaging Spectrometer observations of the Si IV line
during the three flares along with a series of nonlinear force-free
field (NLFFF) extrapolations in order to investigate the conditions that
lead the final flare to be eruptive. From this analysis it is found to
be unlikely that the eruption was triggered by either kink instability
or by tether-cutting reconnection, allowing the flux rope to rise into a
region where it would be susceptible to the torus instability. The NLFFF
modeling does, however, suggest that the overlying magnetic field has a
fan-spine topology, raising the possibility that breakout reconnection
occurring during the first two flares weakened the overlying field,
allowing the flux rope to erupt in the subsequent third flare.
---------------------------------------------------------
Title: Locating Hot Plasma in Small Flares using Spectroscopic
Overlappogram Data from the Hinode EUV Imaging Spectrometer
Authors: Harra, Louise; Matthews, Sarah; Long, David; Hasegawa,
Takahiro; Lee, Kyoung-Sun; Reeves, Katharine K.; Shimizu, Toshifumi;
Hara, Hirohisa; Woods, Magnus
2020SoPh..295...34H Altcode: 2020arXiv200302908H
One of the key processes associated with the "standard" flare model is
chromospheric evaporation, a process during which plasma heated to high
temperatures by energy deposition at the flare footpoints is driven
upwards into the corona. Despite several decades of study, a number
of open questions remain, including the relationship between plasma
produced during this process and observations of earlier "superhot"
plasma. The Extreme ultraviolet Imaging Spectrometer (EIS) onboard
Hinode has a wide slot, which is often used as a flare trigger in the
He II emission-line band. Once the intensity passes a threshold level,
the study will switch to one focussed on the flaring region. However,
when the intensity is not high enough to reach the flare trigger
threshold, these datasets are then available during the entire flare
period and provide high-cadence spectroscopic observations over a
large field of view. We make use of data from two such studies of a
C4.7 flare and a C1.6 flare to probe the relationship between hot Fe
XXIV plasma and plasmas observed by the Reuven Ramaty High Energy Solar
Spectroscopic Imager (RHESSI) and the X-ray Telescope (XRT) to track
where the emission comes from and when it begins. The flare trigger
slot data used in our analysis has one-minute cadence. Although the
spatial and spectral information are merged in the wide-slot data,
it is still possible to extract when the hot plasma appears, through
the appearance of the Fe Xxiv spectral image. It is also possible
to derive spectrally pure Fe XXIV light curves from the EIS data,
and compare them with those derived from hard X-rays, enabling a full
exploration of the evolution of hot emission. The Fe XXIV emission
peaks just after the peak in the hard X-ray lightcurve; consistent with
an origin in the evaporation of heated plasma following the transfer
of energy to the lower atmosphere. A peak was also found for the C4.7
flare in the RHESSI peak temperature, which occurred before the hard
X-rays peaked. This suggests that the first peak in hot-plasma emission
is likely to be directly related to the energy-release process.
---------------------------------------------------------
Title: A Two-Sided-Loop X-Ray Solar Coronal Jet and a Sudden
Photospheric Magnetic-field Change, Both Driven by a Minifilament
Eruption
Authors: Sterling, A. C.; Harra, L. K.; Moore, R. L.; Falconer, D. A.
2019AGUFMSH11D3382S Altcode:
Most of the commonly discussed solar coronal jets are of the
type consisting of a <P />single spire extending approximately
vertically from near the solar surface into the <P />corona. Recent
research shows that eruption of a miniature filament (minifilament)
<P />drives at least many such single-spire jets, and concurrently
generates a miniflare at the <P />eruption site. A different type of
coronal jet, identified in X-ray images during the <P />Yohkoh era, are
two-sided-loop jets, which extend from a central excitation location <P
/>in opposite directions, along two opposite low-lying coronal loops
that are more-or-less <P />horizontal to the surface. We observe such
a two-sided-loop jet from the edge of active <P />region (AR) 12473,
using data from Hinode XRT and EIS, and SDO AIA and HMI. Similar <P />to
single-spire jets, this two-sided-loop jet results from eruption of a
minifilament, which <P />accelerates to over 140 km/s before abruptly
stopping upon striking overlying <P />nearly-horizontal magnetic field
at ∼ 30,000 km altitude and producing the two-sided-loop <P />jet
via interchange reconnection. Analysis of EIS raster scans show that
a hot <P />brightening, consistent with a small flare, develops in the
aftermath of the eruption, <P />and that Doppler motions (∼ 40 km/s)
occur near the jet-formation region. As with <P />many single-spire
jets, the trigger of the eruption here is apparently magnetic <P />flux
cancelation, which occurs at a rate of ∼ 4×10^18 Mx/hr, comparable
to the rate <P />observed in some single-spire AR jets. An apparent
increase in the (line-of-sight) <P />flux occurs within minutes of
onset of the minifilament eruption, consistent with the <P />apparent
increase being due to a rapid reconfiguration of low-lying magnetic
field <P />during the minifilament eruption. Details appear in Sterling
et al. (2019, ApJ, 871, 220).
---------------------------------------------------------
Title: Genesis and impulsive evolution of the fast CME associated
with the X8.2 flare on 2017 September 10
Authors: Veronig, A.; Podladchikova, T.; Dissauer, K.; Temmer, M.;
Seaton, D. B.; Long, D.; Guo, J.; Vrsnak, B.; Harra, L. K.; Kliem, B.
2019AGUFMSH13A..02V Altcode:
The X8.2 event of 2017 September 10 provides unique observations to
study the genesis, magnetic morphology, impulsive dynamics and shock
formation in a very fast coronal mass ejection (CME). As will be
discussed in this presentation, fundamental insight in the processes
of magnetic reconnection, CME acceleration and shock formation are
provided through EUV observations of the middle corona. <P />Combining
the large field-of-view and high-cadence imagery from GOES-16/SUVI
and SDO/AIA EUV, respectively, we identify a hot (T ≈ 10-15 MK)
bright rim around a quickly expanding cavity, embedded inside a much
larger CME shell (T ≈ 1-2 MK). The CME shell develops from a dense
set of large AR loops (>0.5Rs) and seamlessly evolves into the
CME front observed in LASCO C2. The strong lateral overexpansion
of the CME shell acts as a piston initiating the fast and globally
propagating EUV shock wave. The hot cavity rim is demonstrated to be
a manifestation of the dominantly poloidal flux and frozen-in plasma
added to the rising flux rope by magnetic reconnection in the current
sheet beneath. The same structure is later observed as the core of the
white-light CME, challenging the traditional interpretation of the CME
three-part morphology (Veronig et al. 2018). <P />The large amount of
added magnetic flux suggested by these observations can explain the
extreme accelerations of the radial and lateral expansion of the CME
shell and cavity, all reaching values up to 5-10 km s<SUP>-2</SUP>. The
acceleration peaks occur simultaneously with the first RHESSI 100-300
keV hard X-ray burst of the associated flare, further underlining the
importance of the reconnection process for the impulsive CME evolution
in the low and middle corona.
---------------------------------------------------------
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz,
W. K.; Schühle, U.
2019AGUFMSH21D3291R Altcode:
The Extreme Ultraviolet Imager (EUI) is part of the remote sensing
instrument package of the ESA/NASA Solar Orbiter mission that will
explore the inner heliosphere and observe the Sun from vantage points
close to the Sun and out-of-the-ecliptic. <P />EUI aims at improving our
understanding of the structure and dynamics of the solar atmosphere. EUI
will take images of the solar atmosphere, globally as well as at high
resolution, and from high solar latitude perspectives. <P />EUI consists
of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm
and 30.4 nm to provide a coverage from chromosphere up to corona. EUI
is designed to cope with the strong constraints that Solar Orbiter has
as a deep space mission. Limited telemetry availability is compensated
by state-of-the-art image compression, on board image processing and
event selection. The imposed power limitations and potentially harsh
radiation environment lead to the usage of novel CMOS sensors. As
the unobstructed field of view of the telescopes needs to protrude
through the spacecraft heat shield, the apertures were kept as small as
possible. This lead to a systematic effort to optimize the throughput
of every optical element and the reduction of noise levels in the
sensor. <P />In this paper we review the design of the two elements of
the EUI instrument: the Optical Bench System and the Common Electronic
Box. Particular attention is also given to the on board software,
the intended operations, the ground software and the foreseen data
products. <P />EUI will bring unique science opportunities thanks to its
specific design, its viewpoint and thanks to the planned synergies with
the other Solar Orbiter instruments. We highlight in particular science
opportunities brought by the out-of-ecliptic vantage point of the solar
poles, the high resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
---------------------------------------------------------
Title: Active Region Modulation of Coronal Hole Solar Wind
Authors: Macneil, Allan R.; Owen, Christopher J.; Baker, Deborah;
Brooks, David H.; Harra, Louise K.; Long, David M.; Wicks, Robert T.
2019ApJ...887..146M Altcode:
Active regions (ARs) are a candidate source of the slow solar wind
(SW), the origins of which are a topic of ongoing research. We present
a case study that examines the processes by which SW is modulated in
the presence of an AR in the vicinity of the SW source. We compare
properties of SW associated with a coronal hole (CH)-quiet Sun boundary
to SW associated with the same CH but one Carrington rotation later,
when this region bordered the newly emerged NOAA AR 12532. Differences
found in a range of in situ parameters are compared between these
rotations in the context of source region mapping and remote sensing
observations. Marked changes exist in the structure and composition of
the SW, which we attribute to the influence of the AR on SW production
from the CH boundary. These unique observations suggest that the
features that emerge in the AR-associated wind are consistent with an
increased occurrence of interchange reconnection during SW production,
compared with the initial quiet Sun case.
---------------------------------------------------------
Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
2019PASJ...71R...1H Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.
---------------------------------------------------------
Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
2019SPIE11118E..07S Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
---------------------------------------------------------
Title: A Two-Sided-Loop X-Ray Solar Coronal Jet and a Sudden
Photospheric Magnetic-field Change, Both Driven by a Minifilament
Eruption
Authors: Sterling, Alphonse C.; Harra, Louise; Moore, Ronald L.;
Falconer, David
2019AAS...23431701S Altcode:
Most of the commonly discussed solar coronal jets are of the type
consisting of a single spire extending approximately vertically from
near the solar surface into the corona. Recent research shows that
eruption of a miniature filament (minifilament) drives at least many
such single-spire jets, and concurrently generates a miniflare at the
eruption site. A different type of coronal jet, identified in X-ray
images during the Yohkoh era, are two-sided-loop jets, which extend
from a central excitation location in opposite directions, along two
opposite low-lying coronal loops that are more-or-less horizontal
to the surface. We observe such a two-sided-loop jet from the edge
of active region (AR) 12473, using data from Hinode XRT and EIS, and
SDO AIA and HMI. Similar to single-spire jets, this two-sided-loop jet
results from eruption of a minifilament, which accelerates to over 140
km/s before abruptly stopping upon striking overlying nearly-horizontal
magnetic field at ∼30,000 km altitude and producing the two-sided-loop
jet via interchange reconnection. Analysis of EIS raster scans show
that a hot brightening, consistent with a small flare, develops in
the aftermath of the eruption, and that Doppler motions (∼40 km/s)
occur near the jet-formation region. As with many single-spire jets, the
trigger of the eruption here is apparently magnetic flux cancelation,
which occurs at a rate of ∼4×10<SUP>18</SUP> Mx/hr, comparable to the
rate observed in some single-spire AR jets. An apparent increase in the
(line-of-sight) flux occurs within minutes of onset of the minifilament
eruption, consistent with the apparent increase being due to a rapid
reconfiguration of low-lying magnetic field during the minifilament
eruption. Details appear in Sterling et al. (2019, ApJ, 871, 220).
---------------------------------------------------------
Title: Comprehensive Determination of the Hinode/EIS Roll Angle
Authors: Pelouze, Gabriel; Auchère, Frédéric; Bocchialini, Karine;
Harra, Louise; Baker, Deborah; Warren, Harry P.; Brooks, David H.;
Mariska, John T.
2019SoPh..294...59P Altcode: 2019arXiv190311923P
We present a new coalignment method for the EUV Imaging Spectrometer
(EIS) on board the Hinode spacecraft. In addition to the pointing
offset and spacecraft jitter, this method determines the roll angle
of the instrument, which has never been systematically measured, and
which is therefore usually not corrected. The optimal pointing for EIS
is computed by maximizing the cross-correlations of the Fe XII 195.119
Å line with images from the 193 Å band of the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory (SDO). By
coaligning 3336 rasters with high signal-to-noise ratio, we estimate
the rotation angle between EIS and AIA and explore the distribution
of its values. We report an average value of (−0.387<SUP>±0.007 )
∘</SUP>. We also provide a software implementation of this method
that can be used to coalign any EIS raster.
---------------------------------------------------------
Title: Genesis, magnetic morphology and impulsive evolution of
the coronal mass ejection associated with the X8.2 flare on 2017
September 10
Authors: Veronig, Astrid; Podladchikova, Tatiana; Dissauer, Karin;
Temmer, Manuela; Seaton, Daniel; Long, David; Guo, Jingnan; Vrsnak,
Bojan; Harra, Louise; Kliem, Bernhard
2019EGUGA..21.9243V Altcode:
The extreme X8.2 event of 2017 September 10 provides unique observations
to study the genesis, magnetic morphology, impulsive dynamics and
shock formation in a very fast coronal mass ejection (CME). Combining
GOES-16/SUVI and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15
MK) bright rim around a quickly expanding cavity, embedded inside a
much larger CME shell (T ≈ 1-2 MK). The CME shell develops from a
dense set of large AR loops (>0.5Rs) and seamlessly evolves into
the CME front observed in LASCO C2. The strong lateral overexpansion
of the CME shell acts as a piston initiating the fast EUV shock
wave. The hot cavity rim is demonstrated to be a manifestation of
the dominantly poloidal flux and frozen-in plasma added to the rising
flux rope by magnetic reconnection in the current sheet beneath. The
same structure is later observed as the core of the white-light CME,
challenging the traditional interpretation of the CME three-part
morphology. The large amount of added magnetic flux suggested by these
observations explains the extreme accelerations of the radial and
lateral expansion of the CME shell and cavity, all reaching values
up to 5-10 km s-2. The acceleration peaks occur simultaneously with
the first RHESSI 100-300 keV hard X-ray burst of the associated flare,
further underlining the importance of the reconnection process for the
impulsive CME evolution. Finally, the much higher radial propagation
speed of the flux rope in relation to the CME shell causes a distinct
deformation of the white-light CME front and shock.
---------------------------------------------------------
Title: Origins and Properties of Active Region Solar Wind
Authors: Macneil, Allan; Owen, Christopher; Baker, Deborah; Harra,
Louise; Long, David; Wicks, Robert
2019EGUGA..21.9712M Altcode:
A primary goal of both the recently-launched Parker Solar Probe (PSP)
and upcoming Solar Orbiter (SolO) missions is to identify and explain
the origins of the solar wind. Recent studies have suggested that
active regions (ARs) are the source of a significant fraction of the
solar wind. Of particular interest is the AR contribution to the slow
solar wind; the origins of which are still largely unknown. We present
a case study of a rare opportunity to explain how the solar wind may
emerge from, or be otherwise altered by, an AR, and also to identify the
properties resulting from such a process. A simple backmapping procedure
is applied to combine EUV remote sensing (SDO-AIA and Hinode-EIS) and
in situ (ACE and WIND) observations of the corona and solar wind for
two consecutive Carrington rotations. Contrasting observations during
the latter rotation, when an AR is present at a trailing coronal hole
(CH) boundary, to those during the former, when the AR is yet to emerge,
allows us to isolate the influence of the AR on the solar wind from the
CH boundary in a unique way. This observational strategy is particularly
timely, as the combination of in situ and remote sensing observations,
often from multiple spacecraft, will be critical to the identification
of solar wind origins with PSP and SolO. With this methodology we find
that, as a result of the presence of the AR, there is significant
alteration of solar wind features such as velocity, composition,
structure, and magnetic field orientation. The changes observed when
the AR is present are consistent with the occurrence of interchange
reconnection between AR and CH magnetic fields, which we argue is the
likely mechanism by which the AR solar wind is produced.
---------------------------------------------------------
Title: A Two-sided Loop X-Ray Solar Coronal Jet Driven by a
Minifilament Eruption
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.;
Falconer, David A.
2019ApJ...871..220S Altcode: 2018arXiv181105557S
Most of the commonly discussed solar coronal jets are the type that
consist of a single spire extending approximately vertically from
near the solar surface into the corona. Recent research supports
that eruption of a miniature filament (minifilament) drives many such
single-spire jets and concurrently generates a miniflare at the eruption
site. A different type of coronal jet, identified in X-ray images during
the Yohkoh era, are two-sided loop jets, which extend from a central
excitation location in opposite directions, along low-lying coronal
loops that are more-or-less horizontal to the surface. We observe
such a two-sided loop jet from the edge of active region (AR) 12473,
using data from Hinode X-Ray Telescope (XRT) and Extreme Ultraviolet
Imaging Spectrometer (EIS), and from Solar Dynamics Observatory’s
(SDO) Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic
Imager (HMI). Similar to single-spire jets, this two-sided loop jet
results from eruption of a minifilament, which accelerates to over 140
km s<SUP>-1</SUP> before abruptly stopping after striking an overlying
nearly horizontal-loop field at ∼30,000 km in altitude and producing
the two-sided loop jet. An analysis of EIS raster scans shows that a hot
brightening, consistent with a small flare, develops in the aftermath
of the eruption, and that Doppler motions (∼40 km s<SUP>-1</SUP>)
occur near the jet formation region. As with many single-spire jets, the
magnetic trigger here is apparently flux cancelation, which occurs at
a rate of ∼4 × 10<SUP>18</SUP> Mx hr<SUP>-1</SUP>, broadly similar
to the rates observed in some single-spire quiet-Sun and AR jets. An
apparent increase in the (line-of-sight) flux occurs within minutes of
the onset of the minifilament eruption, consistent with the apparent
increase being due to a rapid reconfiguration of low-lying fields
during and soon after the minifilament-eruption onset.
---------------------------------------------------------
Title: Genesis and Impulsive Evolution of the 2017 September 10
Coronal Mass Ejection
Authors: Veronig, Astrid M.; Podladchikova, Tatiana; Dissauer, Karin;
Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak,
Bojan; Harra, Louise; Kliem, Bernhard
2018ApJ...868..107V Altcode: 2018arXiv181009320V
The X8.2 event of 2017 September 10 provides unique observations
to study the genesis, magnetic morphology, and impulsive dynamics
of a very fast coronal mass ejection (CME). Combining GOES-16/SUVI
and SDO/AIA EUV imagery, we identify a hot (T ≈ 10-15 MK) bright
rim around a quickly expanding cavity, embedded inside a much larger
CME shell (T ≈ 1-2 MK). The CME shell develops from a dense set of
large AR loops (≳0.5R <SUB> s </SUB>) and seamlessly evolves into
the CME front observed in LASCO C2. The strong lateral overexpansion
of the CME shell acts as a piston initiating the fast EUV wave. The
hot cavity rim is demonstrated to be a manifestation of the dominantly
poloidal flux and frozen-in plasma added to the rising flux rope by
magnetic reconnection in the current sheet beneath. The same structure
is later observed as the core of the white-light CME, challenging the
traditional interpretation of the CME three-part morphology. The large
amount of added magnetic flux suggested by these observations explains
the extreme accelerations of the radial and lateral expansion of the CME
shell and cavity, all reaching values of 5-10 km s<SUP>-2</SUP>. The
acceleration peaks occur simultaneously with the first RHESSI 100-300
keV hard X-ray burst of the associated flare, further underlining
the importance of the reconnection process for the impulsive CME
evolution. Finally, the much higher radial propagation speed of the
flux rope in relation to the CME shell causes a distinct deformation
of the white-light CME front and shock.
---------------------------------------------------------
Title: The EUI instrument onboard Solar Orbiter: the EUV corona
imaged differently
Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric;
Harra, Louise; Schmutz, Werner; Schühle, Udo
2018csc..confE..73B Altcode:
The ESA Solar Orbiter mission is designed to determine how the Sun
creates and controls the heliosphere. The spacecraft will bring
a combination of in situ and remote sensing instruments out of the
ecliptic (>30°) and close to the sun (0.3 solar-radii). The launch
of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme
Ultraviolet Imager is part of the remote-sensing package of Solar
Orbiter, to be operating during 3 ten-day periods of each orbit around
the Sun, which last roughly half a year. These 3 periods will correspond
to perihelion and maximal solar latitude north and south. The Extreme
Ultraviolet Imager is itself a suite of three UV and EUV telescopes
that observe the solar atmosphere both globally as well as at very
high resolution. The two high-resolution imagers (HRIs) will image the
solar atmosphere in the chromospheric Lyman alpha line and the coronal
17nm pass band with a resolution of 0.5 arcsec. From perihelion, this
will correspond to a pixel footprint on the solar disc of (110km)^2
. The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV
passbands, will provide a global view of the solar atmosphere and is
therefore an essential building block for the "connection science"
of the Solar Orbiter mission. The FSI field of view is large enough
(228arcmin) that, even at perihelion and at maximal off-points by Solar
Orbiter, the full solar disk remains in the field of view. This large
FOV and the FSI's high sensitivity will allow to image the "transition
corona" where the topology of streamers and pseudo-streamers fades in
the solar wind. Furthermore, FSI will be the first to image all this
from out of the ecliptic. In this talk we will give an overview of the
EUI instrument. We will focus on the novel aspects of EUI that will
allow it to image beyond what previous EUV imagers could show us: EUV
imaging from the highest solar latitude, with the widest field-of-view
and at highest spatial resolution.
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Title: Evolution of flux rope, CME and associated EUV wave in the
10-Sep-2018 X8.2 event
Authors: Podladchikova, Tatiana; Veronig, Astrid M.; Dissauer, Karin;
Temmer, Manuela; Seaton, Daniel B.; Long, David; Guo, Jingnan; Vršnak,
Bojan; Harra, Louise; Kliem, Bernhard
2018csc..confE..38P Altcode:
We combine the high-cadence and large field-of-view EUV imagery of
the Atmospheric Imaging Assembly (AIA) onboard SDO and the Solar
Ultraviolet Imager (SUVI) onboard GOES-16 to study the origin and
impulsive evolution of the fast CME that originated in the September
10th 2017 X8.2 event as well as the initiation of the associated EUV
wave. In the LASCO field-of-view, the CME reveals speeds >3000
km/s. In the low-to-mid corona, it shows a distinct bubble in the EUV
imagery that reveals a significant lateral overexpansion. In addition,
is also shows a distinct expanding cavity that is interpreted as
manifestation of the flux rope driving the eruption. We present a method
to automatically identify and segment the CME bubble in SUVI images and
to derive its radial and lateral evolution up to about 2 solar radii,
in terms of velocity and acceleration. These measurements are set into
context with the evolution of the embedded flux rope/cavity observed by
AIA. The observations show clear signatures of new poloidal flux added
to the flux rope by magnetic reconnection in the current sheet beneath
the eruptive structure, which is important for the high accelerations
observed in this event. The radial propagation of the CME shell revealed
a peak value of the acceleration of about 5.3 km/s2, whereas the lateral
expansion reached a peak value of 10.1 km/s2, which is the largest value
reported so far. The flux rope/cavity reveals a radial acceleration of
6.7 km/s2 and lateral acceleration of 5.3 km/s2. We note that at this
early evolution phase, the speed of the cavity/flux rope is higher
than that of the CME bubble (front). The EUV wave associated with
this eruption was observed by AIA, SUVI and STEREO-A EUVI, which had
a separation angle with Earth of 128°, and the common field of view
of the spacecraft was 52°. AIA and SUVI images above the solar limb
reveal the initiation of the EUV wave by the accelerating flanks of
the CME bubble, followed by detachment and propagation of the wave
with a speed of 1100 km/s. The EUV wave shows a global propagation
over the full hemisphere visible to Earth view as well as into the
STEREO-A field-of-view. We study the propagation and kinematics of
the direct as well as the various reflected and refracted EUV wave
components on the solar sphere, finding speeds in the range from 370
to 1010 km/s. Finally, we note that this EUV wave is also distinct as
it reveals propagation and transmission through the polar coronal holes.
---------------------------------------------------------
Title: Coronal and chromospheric observations of pre- and post-flare
plasma evolution
Authors: Long, David; Reid, Aaron; Harra, Louise; Mathioudakis, Mihalis
2018csc..confE..16L Altcode:
Solar flares are among the most energetic and spectacular events
occurring in our solar system, produced by the release of stored
magnetic energy in the solar atmosphere through the reconnection
of twisted magnetic fields. Although the magnetic field itself is
difficult to observe in the solar atmosphere, we can gain vital
insights into the reconnection process by studying the evolution
of solar plasma prior to and following the flare. Here we present
contemporaneous spectroscopic and imaging observations of an X9.3 solar
flare from 2017-September-6. This was the largest flare of the current
solar cycle to date, and was well observed in the corona by SDO/AIA
and Hinode/EIS as well as in the chromosphere by instruments at the
ground-based Swedish Solar Telescope. This combination of observations
provides spectroscopic information throughout the solar atmosphere,
giving a unique insight into the evolution of plasma in the lead-up
to and following the flare.
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Title: Probing the evolution of a coronal cavity within a solar
coronal mass ejection.
Authors: Harra, Louise K.; Doschek, G. A.; Hara, Hirohisa; Long,
David; Warren, Harry; Matthews, Sarah; Lee, Kyoung-Sun; Jenkins, Jack
2018cosp...42E1381H Altcode:
On the 10 September 2017, an X-class solar flare erupted at the solar
limb. The associated coronal mass ejection (CME) had the classic three
part structure with a bright core surrounded by a dark cavity. This
event was captured perfectly by the Hinode EUV imaging spectrometer
(EIS). The EIS instrument captured spectroscopically the flaring
loops, the current sheet and the cavity for the first time. In the
'standard flare model', magnetic reconnection of coronal loops occurs
following the eruption of a magnetic flux rope. The flux rope is a key
element of the flare process and eruption but is inherently difficult
to observe. Dark cavities observed within a CME are assumed to be
flux ropes. The observations we describe here, provide an insight
into the characteristics of a cavity, and how the rapid injection of
energy from the flare underneath forces the rapid expansion of the
flux rope resulting in the eruption. Doppler shifts of over 200 km/s
are measured at either end of the cavity. There is mixed temperature
plasma - cool material in the centre that also has strong flows, and
hot FeXXIV emission being observed. SDO Atmospheric Imaging Assembly
(AIA) data shows that the cavity erupts rapidly, and is being driven
by the non-thermal energy input from the flare below as measured from
Fermi data.
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Title: The EUI flight instrument of Solar Orbiter: from optical
alignment to end-to-end calibration
Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.;
Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado,
R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.;
Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin,
M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli,
A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.;
Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P.
2018SPIE10699E..0HH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter
mission will image the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral
ranges. The development of the EUI instrument has been successfully
completed with the optical alignment of its three channels' telescope,
the thermal and mechanical environmental verification, the electrical
and software validations, and an end-toend on-ground calibration of
the two-units' flight instrument at the operating wavelengths. The
instrument has been delivered and installed on the Solar Orbiter
spacecraft, which is now undergoing all preparatory activities before
launch.
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Title: The Triggering of the 2014 March 29 Filament Eruption
Authors: Woods, Magnus M.; Inoue, Satoshi; Harra, Louise K.; Matthews,
Sarah A.; Kusano, Kanya; Kalmoni, Nadine M. E.
2018ApJ...860..163W Altcode: 2018arXiv180505976W
The X1 flare and associated filament eruption occurring in NOAA
Active Region 12017 on SOL2014-03-29 has been a source of intense
study. In this work, we analyze the results of a series of nonlinear
force-free field extrapolations of the flare’s pre- and post-flare
periods. In combination with observational data provided by the IRIS,
Hinode, and Solar Dynamics Observatory missions, we have confirmed the
existence of two flux ropes present within the active region prior
to flaring. Of these two flux ropes, we find that intriguingly only
one erupts during the X1 flare. We propose that the reason for this
is due to tether cutting reconnection allowing one of the flux ropes
to rise to a torus unstable region prior to flaring, thus allowing it
to erupt during the subsequent flare.
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Title: Mapping the Solar Wind to Its Source to Compare Coronal and
Heliospheric Boundaries
Authors: Macneil, Allan; Owen, Christopher; Wicks, Robert; Harra,
Louise; Long, David
2018EGUGA..2015465M Altcode:
We aim to understand the relationship between the observational
properties of coronal holes, particularly their boundaries, and the
composition of their associated solar wind. These are anomalous in that
while the coronal boundaries appear sharp, the associated transition in
solar wind ionisation and elemental abundance appears quite smooth. To
do so we employ the standard two-step solar wind mapping technique;
first assuming a constant and purely radial solar wind to map back to
the source surface of a potential field source surface (PFSS) model,
and then using field lines derived from this to select the likely source
region at 1 solar radius. Such mapping techniques are of increasing
importance as we approach the launch of Solar Orbiter, which aims to
establish an unprecedented link between in situ and remote sensing
observations. We find that despite its simplicity this technique maps
compositionally cool (low charge-state) solar wind plasma back to the
anticipated coronal hole source regions. Further, we test the agreement
of features in the solar wind with both structure from EUV coronal
images and the modelled magnetic field direction to test the quality
of the backmapping and make adjustments to the technique. We directly
compare heavy ion charge states observed in situ to coronal properties
inferred from EUV data. We will present results and offer explanations
for the evolution of solar wind charge state relative to the properties
across source regions, in particular for the anomalous coronal hole
boundaries. We will also analyse the viability of the chosen mapping
technique for this study, and for others with Solar Orbiter.
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Title: Plasma Evolution within an Erupting Coronal Cavity
Authors: Long, David M.; Harra, Louise K.; Matthews, Sarah A.; Warren,
Harry P.; Lee, Kyoung-Sun; Doschek, George A.; Hara, Hirohisa; Jenkins,
Jack M.
2018ApJ...855...74L Altcode: 2018arXiv180201391L
Coronal cavities have previously been observed to be associated
with long-lived quiescent filaments and are thought to correspond
to the associated magnetic flux rope. Although the standard flare
model predicts a coronal cavity corresponding to the erupting flux
rope, these have only been observed using broadband imaging data,
restricting an analysis to the plane-of-sky. We present a unique set of
spectroscopic observations of an active region filament seen erupting
at the solar limb in the extreme ultraviolet. The cavity erupted and
expanded rapidly, with the change in rise phase contemporaneous with an
increase in nonthermal electron energy flux of the associated flare. Hot
and cool filamentary material was observed to rise with the erupting
flux rope, disappearing suddenly as the cavity appeared. Although
strongly blueshifted plasma continued to be observed flowing from
the apex of the erupting flux rope, this outflow soon ceased. These
results indicate that the sudden injection of energy from the flare
beneath forced the rapid eruption and expansion of the flux rope,
driving strong plasma flows, which resulted in the eruption of an
under-dense filamentary flux rope.
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Title: Photospheric and Coronal Abundances in an X8.3 Class Limb Flare
Authors: Doschek, G. A.; Warren, H. P.; Harra, L. K.; Culhane, J. L.;
Watanabe, T.; Hara, H.
2018ApJ...853..178D Altcode:
We analyze solar elemental abundances in coronal post-flare
loops of an X8.3 flare (SOL2017-09-10T16:06) observed on the west
limb on 2017 September 10 near 18 UT using spectra recorded by
the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode
spacecraft. The abundances in the corona can differ from photospheric
abundances due to the first ionization potential (FIP) effect. In
some loops of this flare, we find that the abundances appear to be
coronal at the loop apices or cusps, but steadily transform from
coronal to photospheric as the loop footpoint is approached. This
result is found from the intensity ratio of a low-FIP ion spectral
line (Ca XIV) to a high-FIP ion spectral line (Ar XIV) formed at
about the same temperature (4-5 MK). Both lines are observed close in
wavelength. Temperature, which could alter the interpretation, does
not appear to be a factor based on intensity ratios of Ca XV lines
to a Ca XIV line. We discuss the abundance result in terms of the
Laming model of the FIP effect, which is explained by the action of
the ponderomotive force in magnetohydrodynamic (MHD) waves in coronal
loops and in the underlying chromosphere.
---------------------------------------------------------
Title: The First Decade of Hinode: Understanding Coronal Mass
Ejections
Authors: Harra, Louise
2018ASSL..449..149H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-thermal distributions and energy transport in the solar
flares
Authors: Matthews, Sarah; del Zanna, Guilio; Calcines, Ariadna;
Mason, Helen; Mathioudakis, Mihalis; Culhane, Len; Harra, Louise;
van Driel-Gesztelyi, Lidia; Green, Lucie; Long, David; Baker, Deb;
Valori, Gherardo
2017arXiv171200773M Altcode:
Determining the energy transport mechanisms in flares remains a central
goal in solar flares physics that is still not adequately answered
by the 'standard flare model'. In particular, the relative roles of
particles and/or waves as transport mechanisms, the contributions of low
energy protons and ions to the overall flare budget, and the limits of
low energy non-thermal electron distribution are questions that still
cannot be adequately reconciled with current instrumentation. In this
'White Paper' submitted in response to the call for inputs to the Next
Generation Solar Physics Mission review process initiated by JAXA,
NASA and ESA in 2016, we outline the open questions in this area and
possible instrumentation that could provide the required observations
to help answer these and other flare-related questions.
---------------------------------------------------------
Title: Fine Structure and Dynamics of the Solar Atmosphere
Authors: Vargas Domínguez, S.; Kosovichev, A. G.; Antolin, P.;
Harra, L.
2017IAUS..327.....V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Properties of Solar Active Regions that Govern Large
Solar Flares and Eruptions
Authors: Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise; Hudson,
Hugh S.; Nagashima, Kaori
2017SPD....4820001T Altcode:
Strong flares and CMEs are often produced from active regions (ARs). In
order to better understand the magnetic properties and evolutions of
such ARs, we conducted statistical investigations on the SDO/HMI and
AIA data of all flare events with GOES levels >M5.0 within 45 deg
from the disk center for 6 years from May 2010 (from the beginning to
the declining phase of solar cycle 24). Out of the total of 51 flares
from 29 ARs, more than 80% have delta-sunspots and about 15% violate
Hale’s polarity rule. We obtained several key findings including
(1) the flare duration is linearly proportional to the separation
of the flare ribbons (i.e., scale of reconnecting magnetic fields)
and (2) CME-eruptive events have smaller sunspot areas. Depending on
the magnetic properties, flaring ARs can be categorized into several
groups, such as spot-spot, in which a highly-sheared polarity inversion
line is formed between two large sunspots, and spot-satellite, where a
newly-emerging flux next to a mature sunspot triggers a compact flare
event. These results point to the possibility that magnetic structures
of the ARs determine the characteristics of flares and CMEs. In the
presentation, we will also show new results from the systematic flux
emergence simulations of delta-sunspot formation and discuss the
evolution processes of flaring ARs.
---------------------------------------------------------
Title: Measuring Velocities in the Early Stage of an Eruption:
Using “Overlappogram” Data from Hinode EIS
Authors: Harra, Louise K.; Hara, Hirohisa; Doschek, George A.;
Matthews, Sarah; Warren, Harry; Culhane, J. Leonard; Woods, Magnus M.
2017ApJ...842...58H Altcode:
In order to understand the onset phase of a solar eruption, plasma
parameter measurements in the early phases are key to constraining
models. There are two current instrument types that allow us to make
such measurements: narrow-band imagers and spectrometers. In the
former case, even narrow-band filters contain multiple emission lines,
creating some temperature confusion. With imagers, however, rapid
cadences are achievable and the field of view can be large. Velocities
of the erupting structures can be measured by feature tracking. In the
spectrometer case, slit spectrometers can provide spectrally pure images
by “rastering” the slit to build up an image. This method provides
limited temporal resolution, but the plasma parameters can be accurately
measured, including velocities along the line of sight. Both methods
have benefits and are often used in tandem. In this paper we demonstrate
for the first time that data from the wide slot on the Hinode EUV
Imaging Spectrometer, along with imaging data from AIA, can be used to
deconvolve velocity information at the start of an eruption, providing
line-of-sight velocities across an extended field of view. Using He
II 256 Å slot data at flare onset, we observe broadening or shift(s)
of the emission line of up to ±280 km s<SUP>-1</SUP>. These are seen at
different locations—the redshifted plasma is seen where the hard X-ray
source is later seen (energy deposition site). In addition, blueshifted
plasma shows the very early onset of the fast rise of the filament.
---------------------------------------------------------
Title: A study of the long term evolution in active region upflows
Authors: Harra, Louise K.; Ugarte-Urra, Ignacio; De Rosa, Marc;
Mandrini, Cristina; van Driel-Gesztelyi, Lidia; Baker, Deborah;
Culhane, J. Leonard; Démoulin, Pascal
2017PASJ...69...47H Altcode:
Since their discovery, upflows at the edges of active regions have
attracted a lot of interest, primarily as they could potentially
contribute to the slow solar wind. One aspect that has not been studied
yet is how the long term evolution of active regions impacts the
upflows. In this work, we analyze one active region that survives three
solar rotations. We track how the flows change with time. We use local
and global modeling of the decaying active region to determine how the
age of the active region will impact the extent of the open magnetic
fields, and then how some of the upflows could become outflows. We
finish with a discussion of how these results, set in a broader context,
can be further developed with the Solar Orbiter mission.
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Title: Turbulent Kinetic Energy in the Energy Balance of a Solar Flare
Authors: Kontar, E. P.; Perez, J. E.; Harra, L. K.; Kuznetsov, A. A.;
Emslie, A. G.; Jeffrey, N. L. S.; Bian, N. H.; Dennis, B. R.
2017PhRvL.118o5101K Altcode: 2017arXiv170302392K
The energy released in solar flares derives from a reconfiguration of
magnetic fields to a lower energy state, and is manifested in several
forms, including bulk kinetic energy of the coronal mass ejection,
acceleration of electrons and ions, and enhanced thermal energy that
is ultimately radiated away across the electromagnetic spectrum
from optical to x rays. Using an unprecedented set of coordinated
observations, from a suite of instruments, we here report on a
hitherto largely overlooked energy component—the kinetic energy
associated with small-scale turbulent mass motions. We show that the
spatial location of, and timing of the peak in, turbulent kinetic
energy together provide persuasive evidence that turbulent energy may
play a key role in the transfer of energy in solar flares. Although
the kinetic energy of turbulent motions accounts, at any given time,
for only ∼(0.5 - 1 )% of the energy released, its relatively rapid
(∼1 - 10 s ) energization and dissipation causes the associated
throughput of energy (i.e., power) to rival that of major components
of the released energy in solar flares, and thus presumably in other
astrophysical acceleration sites.
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Title: Observations and Modelling of the Pre-flare Period of the 29
March 2014 X1 Flare
Authors: Woods, M. M.; Harra, L. K.; Matthews, S. A.; Mackay, D. H.;
Dacie, S.; Long, D. M.
2017SoPh..292...38W Altcode: 2017arXiv170106457W
On 29 March 2014, NOAA Active Region (AR) 12017 produced an X1
flare that was simultaneously observed by an unprecedented number
of observatories. We have investigated the pre-flare period of this
flare from 14:00 UT until 19:00 UT using joint observations made
by the Interface Region Imaging Spectrometer (IRIS) and the Hinode
Extreme Ultraviolet Imaging Spectrometer (EIS). Spectral lines
providing coverage of the solar atmosphere from the chromosphere to
the corona were analysed to investigate pre-flare activity within the
AR. The results of the investigation have revealed evidence of strongly
blue-shifted plasma flows, with velocities up to 200 kms−<SUP>1</SUP>,
being observed 40 minutes prior to flaring. These flows are located
along the filament present in the active region and are both spatially
discrete and transient. In order to constrain the possible explanations
for this activity, we undertake non-potential magnetic field modelling
of the active region. This modelling indicates the existence of a
weakly twisted flux rope along the polarity inversion line in the region
where a filament and the strong pre-flare flows are observed. We then
discuss how these observations relate to the current models of flare
triggering. We conclude that the most likely drivers of the observed
activity are internal reconnection in the flux rope, early onset of the
flare reconnection, or tether-cutting reconnection along the filament.
---------------------------------------------------------
Title: Magnetic Properties of Solar Active Regions That Govern Large
Solar Flares and Eruptions
Authors: Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise K.;
Hudson, Hugh; Nagashima, Kaori
2017ApJ...834...56T Altcode: 2016arXiv161105047T
Solar flares and coronal mass ejections (CMEs), especially the larger
ones, emanate from active regions (ARs). With the aim of understanding
the magnetic properties that govern such flares and eruptions, we
systematically survey all flare events with Geostationary Orbiting
Environmental Satellite levels of ≥M5.0 within 45° from disk center
between 2010 May and 2016 April. These criteria lead to a total of 51
flares from 29 ARs, for which we analyze the observational data obtained
by the Solar Dynamics Observatory. More than 80% of the 29 ARs are found
to exhibit δ-sunspots, and at least three ARs violate Hale’s polarity
rule. The flare durations are approximately proportional to the distance
between the two flare ribbons, to the total magnetic flux inside the
ribbons, and to the ribbon area. From our study, one of the parameters
that clearly determine whether a given flare event is CME-eruptive
or not is the ribbon area normalized by the sunspot area, which may
indicate that the structural relationship between the flaring region
and the entire AR controls CME productivity. AR characterization shows
that even X-class events do not require δ-sunspots or strong-field,
high-gradient polarity inversion lines. An investigation of historical
observational data suggests the possibility that the largest solar
ARs, with magnetic flux of 2 × 10<SUP>23</SUP> Mx, might be able to
produce “superflares” with energies of the order of 10<SUP>34</SUP>
erg. The proportionality between the flare durations and magnetic
energies is consistent with stellar flare observations, suggesting a
common physical background for solar and stellar flares.
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Title: Fundamental Physics of the Slow Solar Wind - What do we Know?
Authors: Ofman, L.; Abbo, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. M.
2016AGUFMSH42A..01O Altcode:
Fundamental physical properties of the slow solar wind (SSW), such
as density, temperature, outflow speed, heavy ion abundances and
charges states were obtained from in-situ measurements at 1AU in
the past from WIND, ACE, and other spacecraft. Plasma and magnetic
field measurement are available as close as 0.3 AU from Helios data,
Spektr-R, and MESSENGER spacecraft. Remote sensing spectroscopic
measurements are available in the corona and below from SOHO/UVCS,
Hinode, and other missions. One of the major objectives of the Solar
Orbiter and Solar Probe Plus missions is to study the sources of the
SSW close to the Sun. The present state of understanding of the physics
of the SSW is based on the combination of the existing observations,
theoretical and numerical 3D MHD and multi-fluid models, that connect
between the SSW sources in the corona and the heliosphere. Recently,
hybrid models that combine fluid electrons and kinetic ions of the
expanding solar wind were developed, and provide further insights of the
local SSW plasma heating processes that related to turbulent magnetic
fluctuations spectra and kinetic ion instabilities observed in the
SSW plasma. These models produce the velocity distribution functions
(VDFs) of the protons and heavier ions as well as the ion anisotropic
temperatures. I will discuss the results of the above observations
and models, and review the current status of our understanding of
the fundamental physics of the SSW. I will review the open questions,
and discuss how they could be addressed with near future observations
and models.
---------------------------------------------------------
Title: Slow Solar Wind: Observations and Modeling
Authors: Abbo, L.; Ofman, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. -K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. -M.
2016SSRv..201...55A Altcode: 2016SSRv..tmp...34A
While it is certain that the fast solar wind originates from coronal
holes, where and how the slow solar wind (SSW) is formed remains an
outstanding question in solar physics even in the post-SOHO era. The
quest for the SSW origin forms a major objective for the planned future
missions such as the Solar Orbiter and Solar Probe Plus. Nonetheless,
results from spacecraft data, combined with theoretical modeling, have
helped to investigate many aspects of the SSW. Fundamental physical
properties of the coronal plasma have been derived from spectroscopic
and imaging remote-sensing data and in situ data, and these results
have provided crucial insights for a deeper understanding of the origin
and acceleration of the SSW. Advanced models of the SSW in coronal
streamers and other structures have been developed using 3D MHD and
multi-fluid equations.
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Title: Properties and Developments of Flaring Active Regions
Authors: Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise K.;
Hudson, Hugh; Nagashima, Kaori
2016usc..confE..15T Altcode:
Larger flares and CMEs are often produced from active regions (ARs). In
order to better understand the magnetic properties and evolutions
of such ARs, we picked up all flare events with GOES levels >M5.0
with heliocentric angles of <45 deg in the period of May 2010 to
April 2016, which led to a total of 29 ARs with 51 flares. We analyzed
the observational data obtained by SDO and found that more than 80%
of the 29 ARs have delta-sunspots. Most of them can be classified
depending on their magnetic structures into (1) spot-spot, where a long
sheared polarity inversion line (PIL: characterized by flare ribbons)
is formed between two major sunspots, and (2) spot-satellite, where
a newly-emerging minor bipole next to a pre-existing spot creates a
compact PIL. The remaining minor groups are (3) quadrupole, where two
emerging bipoles produce a PIL in between, and (4) inter-AR, which
produces flares not from delta-spots but from between two separated
ARs. From statistical investigations we found for example that the
spot-spot group generally shows long-duration events due to large
coronal structures, while the spot-satellite has impulsive events
because of their compact magnetic nature. We will also present flux
emergence simulations and discuss their formation processes.
---------------------------------------------------------
Title: The Characteristics of Solar X-Class Flares and CMEs: A
Paradigm for Stellar Superflares and Eruptions?
Authors: Harra, Louise K.; Schrijver, Carolus J.; Janvier, Miho;
Toriumi, Shin; Hudson, Hugh; Matthews, Sarah; Woods, Magnus M.; Hara,
Hirohisa; Guedel, Manuel; Kowalski, Adam; Osten, Rachel; Kusano,
Kanya; Lueftinger, Theresa
2016SoPh..291.1761H Altcode: 2016SoPh..tmp..111H
This paper explores the characteristics of 42 solar X-class flares that
were observed between February 2011 and November 2014, with data from
the Solar Dynamics Observatory (SDO) and other sources. This flare
list includes nine X-class flares that had no associated CMEs. In
particular our aim was to determine whether a clear signature could
be identified to differentiate powerful flares that have coronal
mass ejections (CMEs) from those that do not. Part of the motivation
for this study is the characterization of the solar paradigm for
flare/CME occurrence as a possible guide to the stellar observations;
hence we emphasize spectroscopic signatures. To do this we ask the
following questions: Do all eruptive flares have long durations? Do
CME-related flares stand out in terms of active-region size vs. flare
duration? Do flare magnitudes correlate with sunspot areas, and, if so,
are eruptive events distinguished? Is the occurrence of CMEs related to
the fraction of the active-region area involved? Do X-class flares with
no eruptions have weaker non-thermal signatures? Is the temperature
dependence of evaporation different in eruptive and non-eruptive
flares? Is EUV dimming only seen in eruptive flares? We find only one
feature consistently associated with CME-related flares specifically:
coronal dimming in lines characteristic of the quiet-Sun corona,
i.e. 1 - 2 MK. We do not find a correlation between flare magnitude
and sunspot areas. Although challenging, it will be of importance to
model dimming for stellar cases and make suitable future plans for
observations in the appropriate wavelength range in order to identify
stellar CMEs consistently.
---------------------------------------------------------
Title: The qualification campaign of the EUI instrument of Solar
Orbiter
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle,
U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Verbeeck, C.; Smith, P.
2016SPIE.9905E..2XH Altcode:
The Extreme Ultraviolet Imager (EUI) instrument is one of the ten
scientific instruments on board the Solar Orbiter mission to be launched
in October 2018. It will provide full-sun and high-resolution images of
the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in
the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument
design has been completed with the Assembly, Integration and Test
(AIT) of the instrument two-units Qualification Model (QM). Optical,
electrical, electro-magnetic compatibility, thermal and mechanical
environmental verifications were conducted and are summarized here. The
integration and test procedures for the Flight Model (FM) instrument
and sub-systems were also verified. Following the Qualification Review,
the flight instrument activities were started with the assembly of
the flight units. The mechanical and thermal acceptance tests and an
end-to-end final calibration in the (E)UV will then be conducted before
delivery for integration on the Solar Orbiter Spacecraft by end of 2016.
---------------------------------------------------------
Title: An Investigation of the Sources of Earth-directed Solar Wind
during Carrington Rotation 2053
Authors: Fazakerley, A. N.; Harra, L. K.; van Driel-Gesztelyi, L.
2016ApJ...823..145F Altcode:
In this work we analyze multiple sources of solar wind through a full
Carrington Rotation (CR 2053) by analyzing the solar data through
spectroscopic observations of the plasma upflow regions and the in
situ data of the wind itself. Following earlier authors, we link solar
and in situ observations by a combination of ballistic backmapping
and potential-field source-surface modeling. We find three sources
of fast solar wind that are low-latitude coronal holes. The coronal
holes do not produce a steady fast wind, but rather a wind with
rapid fluctuations. The coronal spectroscopic data from Hinode’s
Extreme Ultraviolet Imaging Spectrometer show a mixture of upflow
and downflow regions highlighting the complexity of the coronal
hole, with the upflows being dominant. There is a mix of open and
multi-scale closed magnetic fields in this region whose (interchange)
reconnections are consistent with the up- and downflows they generate
being viewed through an optically thin corona, and with the strahl
directions and freeze-in temperatures found in in situ data. At the
boundary of slow and fast wind streams there are three short periods
of enhanced-velocity solar wind, which we term intermediate based on
their in situ characteristics. These are related to active regions that
are located beside coronal holes. The active regions have different
magnetic configurations, from bipolar through tripolar to quadrupolar,
and we discuss the mechanisms to produce this intermediate wind, and
the important role that the open field of coronal holes adjacent to
closed-field active regions plays in the process.
---------------------------------------------------------
Title: A Comparison of Global Magnetic Field Skeletons and
Active-Region Upflows
Authors: Edwards, S. J.; Parnell, C. E.; Harra, L. K.; Culhane, J. L.;
Brooks, D. H.
2016SoPh..291..117E Altcode: 2015SoPh..tmp..161E
Plasma upflows have been detected in active regions using Doppler
velocity maps. The origin and nature of these upflows is not well known
with many of their characteristics determined from the examination
of single events. In particular, some studies suggest these upflows
occur along open field lines and, hence, are linked to sources of
the solar wind. To investigate the relationship these upflows may
have with the solar wind, and to probe what may be driving them, this
paper considers seven active regions observed on the solar disc using
the Extreme ultraviolet Imaging Spectrometer aboard Hinode between
August 2011 and September 2012. Plasma upflows are observed in all
these active regions. The locations of these upflows are compared
to the global potential magnetic field extrapolated from the Solar
Dynamics Observatory, Helioseismic and Magnetic Imager daily synoptic
magnetogram taken on the day the upflows were observed. The structure
of the magnetic field is determined by constructing its magnetic
skeleton in order to help identify open-field regions and also sites
where magnetic reconnection at global features is likely to occur. As
a further comparison, measurements of the temperature, density and
composition of the plasma are taken from regions with active-region
upflows. In most cases the locations of the upflows in the active
regions do not correspond to areas of open field, as predicted by
a global coronal potential-field model, and therefore these upflows
are not always sources of the slow solar wind. The locations of the
upflows are, in general, intersected by separatrix surfaces associated
with null points located high in the corona; these could be important
sites of reconnection with global consequences.
---------------------------------------------------------
Title: Slow Solar Wind: Observable Characteristics for Constraining
Modelling
Authors: Ofman, L.; Abbo, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. M.
2015AGUFMSH11F..03O Altcode:
The Slow Solar Wind (SSW) origin is an open issue in the post SOHO
era and forms a major objective for planned future missions such as
the Solar Orbiter and Solar Probe Plus.Results from spacecraft data,
combined with theoretical modeling, have helped to investigate many
aspects of the SSW. Fundamental physical properties of the coronal
plasma have been derived from spectroscopic and imaging remote-sensing
data and in-situ data, and these results have provided crucial insights
for a deeper understanding of the origin and acceleration of the
SSW.Advances models of the SSW in coronal streamers and other structures
have been developed using 3D MHD and multi-fluid equations.Nevertheless,
there are still debated questions such as:What are the source regions
of SSW? What are their contributions to the SSW?Which is the role
of the magnetic topology in corona for the origin, acceleration and
energy deposition of SSW?Which are the possible acceleration and heating
mechanisms for the SSW?The aim of this study is to present the insights
on the SSW origin and formationarisen during the discussions at the
International Space Science Institute (ISSI) by the Team entitled
”Slowsolar wind sources and acceleration mechanisms in the corona”
held in Bern (Switzerland) in March2014--2015. The attached figure will
be presented to summarize the different hypotheses of the SSW formation.
---------------------------------------------------------
Title: Preface: Probing the Sun Inside and Out
Authors: Harra, Louise; Baker, Deborah; Howe, Rachel; Leibacher,
John; van Driel-Gesztelyi, Lidia
2015SoPh..290.3091H Altcode: 2015SoPh..tmp..167H
No abstract at ADS
---------------------------------------------------------
Title: Persistent Near-Surface Flow Structures from Local
Helioseismology
Authors: Howe, Rachel; Komm, R. W.; Baker, D.; Harra, L.; van
Driel-Gesztelyi, L.; Bogart, R. S.
2015SoPh..290.3137H Altcode: 2015arXiv150706525H; 2015SoPh..tmp..115H
Near-surface flows measured by the ring-diagram technique of local
helioseismology show structures that persist over multiple rotations. We
examine these phenomena using data from the Global Oscillation Network
Group (GONG) and the Helioseismic and Magnetic Imager (HMI) and show
that a correlation analysis of the structures can be used to estimate
the rotation rate as a function of latitude, giving a result consistent
with the near-surface rate from global helioseismology and slightly
slower than that obtained from a similar analysis of the surface
magnetic field strength. At latitudes of 60<SUP>∘</SUP> and above,
the HMI flow data reveal a strong signature of a two-sided zonal flow
structure. This signature may be related to recent reports of "giant
cells" in solar convection.
---------------------------------------------------------
Title: A Study of the Coronal Non-thermal Velocity in Polar Regions
During the Rise from Solar Minimum to Solar Maximum in Cycle 24
Authors: Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.;
van Driel-Gesztelyi, L.
2015SoPh..290.3203H Altcode: 2015SoPh..tmp....8H
We explore the changes in coronal non-thermal velocity (V<SUB>nt</SUB>)
measurements at the poles from solar minimum to solar maximum using
Hinode EUV Imaging Spectrometer data. We find that although the
intensity in the corona at the poles does tend to increase with
the cycle, there are no significant changes in the V<SUB>nt</SUB>
values. The locations of enhanced V<SUB>nt</SUB> values measured do not
always have a counterpart in intensity, and they are sometimes located
in weak emission regions. Unipolar magnetic streams, created through
diffusion of the following polarity of the decaying active regions,
slowly progress towards the poles. These streams are expected to
be related to magnetic nulls as locations that indicate an increased
likelihood for magnetic reconnection to occur. Through global potential
field source-surface modelling, we determine how the number of nulls
varied during the cycle and find that those that lie at < 1.1
solar radii vary significantly. We search for a correlation between
the variation of the magnetic nulls and the V<SUB>nt</SUB> values,
as it may be expected that with an increasing number of nulls, the
V<SUB>nt</SUB> values in the corona increase as well. There is no
correlation with the V<SUB>nt</SUB> values, however. This indicates
that the magnetic structures that create the enhanced V<SUB>nt</SUB>
behaviour are small-scale features and hence not easily measurable at
the poles. Because they do not change during the solar cycle, they are
likely to be created by a local dynamo. The variation of the upper
range of V<SUB>nt</SUB> is reduced, which highlights that strongly
dynamic behaviour is reduced as the solar maximum approaches. This
is likely to be due to the reduced area of the polar coronal hole,
which allows fewer opportunities for reconnection to occur between
open and closed magnetic fields.
---------------------------------------------------------
Title: Spectroscopic Signatures Related to a Sunquake
Authors: Matthews, S. A.; Harra, L. K.; Zharkov, S.; Green, L. M.
2015ApJ...812...35M Altcode: 2015arXiv150807216M
The presence of flare-related acoustic emission (sunquakes (SQs))
in some flares, and only in specific locations within the flaring
environment, represents a severe challenge to our current understanding
of flare energy transport processes. In an attempt to contribute
to understanding the origins of SQs we present a comparison of
new spectral observations from Hinode’s EUV imaging Spectrometer
(EIS) and the Interface Region Imaging Spectrograph (IRIS) of the
chromosphere, transition region, and corona above an SQ, and compare
them to the spectra observed in a part of the flaring region with
no acoustic signature. Evidence for the SQ is determined using both
time-distance and acoustic holography methods, and we find that unlike
many previous SQ detections, the signal is rather dispersed, but that
the time-distance and 6 and 7 mHz sources converge at the same spatial
location. We also see some evidence for different evolution at different
frequencies, with an earlier peak at 7 mHz than at 6 mHz. Using EIS
and IRIS spectroscopic measurements we find that in this location, at
the time of the 7 mHz peak the spectral emission is significantly more
intense, shows larger velocity shifts and substantially broader profiles
than in the location with no SQ, and there is a good correlation between
blueshifted, hot coronal, hard X-ray (HXR), and redshifted chromospheric
emission, consistent with the idea of a strong downward motion driven by
rapid heating by nonthermal electrons and the formation of chromospheric
shocks. Exploiting the diagnostic potential of the Mg ii triplet lines,
we also find evidence for a single large temperature increase deep in
the atmosphere, which is consistent with this scenario. The time of the
6 mHz and time-distance peak signal coincides with a secondary peak
in the energy release process, but in this case we find no evidence
of HXR emission in the quake location, instead finding very broad
spectral lines, strongly shifted to the red, indicating the possible
presence of a significant flux of downward propagating Alfvén waves.
---------------------------------------------------------
Title: The extreme UV imager telescope on-board the Solar Orbiter
mission: overview of phase C and D
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques,
L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz,
W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo,
M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C.
2015SPIE.9604E..0GH Altcode:
The Solar Orbiter mission is composed of ten scientific instruments
dedicated to the observation of the Sun's atmosphere and its
heliosphere, taking advantage of an out-of ecliptic orbit and at
perihelion reaching a proximity close to 0.28 A.U. On board Solar
Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun
image sequences of the solar corona in the extreme ultraviolet (17.1
nm and 30.4 nm), and high-resolution image sequences of the solar disk
in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet
(121.6 nm). The EUI concept uses heritage from previous similar extreme
ultraviolet instrument. Additional constraints from the specific orbit
(thermal and radiation environment, limited telemetry download) however
required dedicated technologies to achieve the scientific objectives
of the mission. The development phase C of the instrument and its
sub-systems has been successfully completed, including thermomechanical
and electrical design validations with the Structural Thermal Model
(STM) and the Engineering Model (EM). The instrument STM and EM units
have been integrated on the respective spacecraft models and will
undergo the system level tests. In parallel, the Phase D has been
started with the sub-system qualifications and the flight parts
manufacturing. The next steps of the EUI development will be the
instrument Qualification Model (QM) integration and qualification
tests. The Flight Model (FM) instrument activities will then follow
with the acceptance tests and calibration campaigns.
---------------------------------------------------------
Title: Astronomical techniques in intensive care
Authors: Harra, Louise K.; Pollard, Tom; Williams, David; Fong, Kevin
2015A&G....56c3.18H Altcode:
Louise K Harra, Tom Pollard, Dave Williams and Kevin Fong describe a
collaboration that uses methods developed for solar astrophysics to
support critically ill patients.
---------------------------------------------------------
Title: Analysis of a coronal mass ejection and corotating interaction
region as they travel from the Sun passing Venus, Earth, Mars,
and Saturn
Authors: Prise, A. J.; Harra, L. K.; Matthews, S. A.; Arridge, C. S.;
Achilleos, N.
2015JGRA..120.1566P Altcode:
During June 2010 a good alignment in the solar system between Venus,
STEREO-B, Mars, and Saturn provided an excellent opportunity to study
the propagation of a coronal mass ejection (CME) and closely occurring
corotating interaction region (CIR) from the Sun to Saturn. The CME
erupted from the Sun at 01:30 UT on 20 June 2010,with v≈ 600 km
s<SUP>-1</SUP>, as observed by STEREO-B, Solar Dynamics Observatory,
and SOHO/Large Angle and Spectrometric Coronagraph. It arrived at
Venus over 2 days later, some 3.5 days after a CIR is also detected
here. The CIR was also observed at STEREO-B and Mars, prior to the
arrival of the CME. The CME is not directed earthward, but the CIR
is detected here less than 2 days after its arrival at Mars. Around
a month later, a strong compression of the Saturn magnetosphere is
observed by Cassini, consistent with the scenario that the CME and CIR
have merged into a single solar transient. The arrival times of both
the CME and the CIR at different locations were predicted using the
ENLIL solar wind model. The arrival time of the CME at Venus, STEREO-B,
and Mars is predicted to within 20 h of its actual detection, but the
predictions for the CIR showed greater differences from observations,
all over 1.5 days early. More accurate predictions for the CIR were
found by extrapolating the travel time between different locations using
the arrival times and speeds detected by STEREO-B and ACE. We discuss
the implications of these results for understanding the propagation
of solar transients.
---------------------------------------------------------
Title: Atmospheric Response of an Active Region to New Small Flux
Emergence
Authors: Shelton, D.; Harra, L.; Green, L.
2015SoPh..290..753S Altcode: 2014arXiv1412.5623S; 2015SoPh..tmp....5S
We investigate the atmospheric response to a small emerging flux region
(EFR) that occurred in the positive polarity of Active Region 11236
on 23 - 24 June 2011. Data from the Solar Dynamics Observatory's
Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic
Imager (HMI), and Hinode's EUV imaging spectrometer (EIS) are used
to determine the atmospheric response to new flux emerging into a
pre-existing active region. Brightenings are seen forming in the upper
photosphere, chromosphere, and corona over the EFR location whilst
flux cancellation is observed in the photosphere. The impact of the
flux emergence is far reaching, with new large-scale coronal loops
forming up to 43 Mm from the EFR and coronal upflow enhancements of
approximately 10 km s<SUP>−1</SUP> on the north side of the EFR. Jets
are seen forming in the chromosphere and the corona over the emerging
serpentine field. This is the first time that coronal jets have been
seen over the serpentine field.
---------------------------------------------------------
Title: Extreme-ultraviolet Observations of Global Coronal Wave
Rotation
Authors: Attrill, G. D. R.; Long, D. M.; Green, L. M.; Harra, L. K.;
van Driel-Gesztelyi, L.
2014ApJ...796...55A Altcode:
We present evidence of global coronal wave rotation in EUV data from
SOHO/EIT, STEREO/EUVI, and SDO/AIA. The sense of rotation is found
to be consistent with the helicity of the source region (clockwise
for positive helicity, anticlockwise for negative helicity), with the
source regions hosting sigmoidal structures. We also study two coronal
wave events observed by SDO/AIA where no clear rotation (or sigmoid)
is observed. The selected events show supporting evidence that they
all originate with flux rope eruptions. We make comparisons across
this set of observations (both with and without clear sigmoidal
structures). On examining the magnetic configuration of the source
regions, we find that the nonrotation events possess a quadrupolar
magnetic configuration. The coronal waves that do show a rotation
originate from bipolar source regions.
---------------------------------------------------------
Title: Looking closer at the Sun
Authors: Harra, Louise K.
2014Sci...346..305H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Impact of a Filament Eruption on Nearby High-lying
Cool Loops
Authors: Harra, L. K.; Matthews, S. A.; Long, D. M.; Doschek, G. A.;
De Pontieu, B.
2014ApJ...792...93H Altcode: 2014arXiv1409.0377H
The first spectroscopic observations of cool Mg II loops above the
solar limb observed by NASA's Interface Region Imaging Spectrograph
(IRIS) are presented. During the observation period, IRIS is pointed
off-limb, allowing the observation of high-lying loops, which reach
over 70 Mm in height. Low-lying cool loops were observed by the IRIS
slit-jaw camera for the entire four-hour observing window. There is no
evidence of a central reversal in the line profiles, and the Mg II h/k
ratio is approximately two. The Mg II spectral lines show evidence of
complex dynamics in the loops with Doppler velocities reaching ±40
km s<SUP>-1</SUP>. The complex motions seen indicate the presence
of multiple threads in the loops and separate blobs. Toward the end
of the observing period, a filament eruption occurs that forms the
core of a coronal mass ejection. As the filament erupts, it impacts
these high-lying loops, temporarily impeding these complex flows,
most likely due to compression. This causes the plasma motions in the
loops to become blueshifted and then redshifted. The plasma motions
are seen before the loops themselves start to oscillate as they reach
equilibrium following the impact. The ratio of the Mg h/k lines also
increases following the impact of the filament.
---------------------------------------------------------
Title: The extreme UV imager of solar orbiter: from detailed design
to flight model
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.;
Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy,
T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.;
Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith,
P.; Winter, B.
2014SPIE.9144E..08H Altcode:
The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. After the breadboarding and prototyping activities that
focused on key technologies, the EUI project has completed the design
phase and has started the final manufacturing of the instrument and its
validation. The EUI instrument has successfully passed its Critical
Design Review (CDR). The process validated the detailed design of
the Optical Bench unit and of its sub-units (entrance baffles, doors,
mirrors, camera, and filter wheel mechanisms), and of the Electronic
Box unit. In the same timeframe, the Structural and Thermal Model
(STM) test campaign of the two units have been achieved, and allowed
to correlate the associated mathematical models. The lessons learned
from STM and the detailed design served as input to release the
manufacturing of the Qualification Model (QM) and of the Flight Model
(FM). The QM will serve to qualify the instrument units and sub-units,
in advance of the FM acceptance tests and final on-ground calibration.
---------------------------------------------------------
Title: An Investigation of the CME of 3 November 2011 and Its
Associated Widespread Solar Energetic Particle Event
Authors: Prise, A. J.; Harra, L. K.; Matthews, S. A.; Long, D. M.;
Aylward, A. D.
2014SoPh..289.1731P Altcode: 2013arXiv1312.2965P
Multi-spacecraft observations are used to study the in-situ effects of a
large coronal mass ejection (CME) erupting from the farside of the Sun
on 3 November 2011, with particular emphasis on the associated solar
energetic particle (SEP) event. At that time both Solar Terrestrial
Relations Observatory (STEREO) spacecraft were located more than
90 degrees from Earth and could observe the CME eruption directly,
with the CME visible on-disk from STEREO-B and off the limb from
STEREO-A. Signatures of pressure variations in the corona such as
deflected streamers were seen, indicating the presence of a coronal
shock associated with this CME eruption. The evolution of the CME
and an associated extreme-ultraviolet (EUV) wave were studied using
EUV and coronagraph images. It was found that the lateral expansion
of the CME low in the corona closely tracked the propagation of the
EUV wave, with measured velocities of 240±19 km s<SUP>−1</SUP> and
221±15 km s<SUP>−1</SUP> for the CME and wave, respectively. Solar
energetic particles were observed to arrive first at STEREO-A, followed
by electrons at the Wind spacecraft at L<SUB>1</SUB>, then STEREO-B,
and finally protons arrived simultaneously at Wind and STEREO-B. By
carrying out a velocity-dispersion analysis on the particles arriving
at each location, it was found that energetic particles arriving
at STEREO-A were released first and that the release of particles
arriving at STEREO-B was delayed by about 50 minutes. Analysis of
the expansion of the CME to a wider longitude range indicates that
this delay is a result of the time taken for the CME edge to reach
the footpoints of the magnetic-field lines connected to STEREO-B. The
CME expansion is not seen to reach the magnetic footpoint of Wind at
the time of solar-particle release for the particles detected here,
suggesting that these particles may not be associated with this CME.
---------------------------------------------------------
Title: Imaging and Spectroscopic Observations of a Filament Channel
and the Implications for the Nature of Counter-streamings
Authors: Chen, P. F.; Harra, L. K.; Fang, C.
2014ApJ...784...50C Altcode: 2014arXiv1401.4514C
The dynamics of a filament channel are observed with imaging and
spectroscopic telescopes before and during the filament eruption on 2011
January 29. The extreme ultraviolet (EUV) spectral observations reveal
that there are no EUV counterparts of the Hα counter-streamings in the
filament channel, implying that the ubiquitous Hα counter-streamings
found by previous research are mainly due to longitudinal oscillations
of filament threads, which are not in phase between each other. However,
there exist larger-scale patchy counter-streamings in EUV along the
filament channel from one polarity to the other, implying that there
is another component of unidirectional flow (in the range of ±10
km s<SUP>-1</SUP>) inside each filament thread in addition to the
implied longitudinal oscillation. Our results suggest that the flow
direction of the larger-scale patchy counter-streaming plasma in the
EUV is related to the intensity of the plage or active network, with
the upflows being located at brighter areas of the plage and downflows
at the weaker areas. We propose a new method to determine the chirality
of an erupting filament on the basis of the skewness of the conjugate
filament drainage sites. This method suggests that the right-skewed
drainage corresponds to sinistral chirality, whereas the left-skewed
drainage corresponds to dextral chirality.
---------------------------------------------------------
Title: Electric current variations and 3D magnetic configuration of
coronal jets
Authors: Schmieder, Brigitte; Harra, Louise K.; Aulanier, Guillaume;
Guo, Yang; Demoulin, Pascal; Moreno-Insertis, Fernando, , Prof
2014cosp...40E2928S Altcode:
Coronal jets (EUV) were observed by SDO/AIA on September 17, 2010. HMI
and THEMIS measured the vector magnetic field from which we derived the
magnetic flux, the phostospheric velocity and the vertical electric
current. The magnetic configuration was computed with a non linear
force-free approach. The phostospheric current pattern of the recurrent
jets were associated with the quasi-separatrix layers deduced from the
magnetic extrapolation. The large twisted near-by Eiffel-tower-shape
jet was also caused by reconnection in current layers containing a
null point. This jet cannot be classified precisely within either the
quiescent or the blowout jet types. We will show the importance of
the existence of bald patches in the low atmosphere
---------------------------------------------------------
Title: Determining the location of open field regions in active
regions and their potential as source regions of the slow solar wind.
Authors: Harra, Louise K.; Culhane, J. Leonard; Parnell, Clare;
Brooks, David; Platten, Sarah
2014cosp...40E1158H Altcode:
One of the significant discoveries from the Hinode EUV Imaging
Spectrometer (EIS) instrument is the observation of persistent upflows
at edges of active regions. These had been observed in the pre-Hinode
era with TRACE imaging, and with SOHO. However, with Hinode these
upflows are now observed regularly spectroscopically, and are seen
in some form in every active region observed. These tend to occur
in regions of low intensity. Although the upflows are always seen,
it is far from clear whether they form part of the plasma that flows
out into the heliosphere. In this work, we study six active regions in
various time periods, with different characteristics - not all are in
the same hemisphere, some are located next to coronal holes, others
are not. All of them show upflowing plasma. Our aim is to study each
active region and compare their physical characteristics. We will then
carry out modelling to determine where the truly open magnetic field
is, and correlate this with the observations. We want to attempt to
distinguish between open and closed field regions. If this can be done
in a consistent and fast way, this would prove to be extremely valuable
in understanding the source of the slow solar wind. Indeed in terms of
a practical use, it could be used as a tool for choosing regions to
observe for the future Solar Orbiter mission - the purpose of which
is to understand the source of the solar wind from its creation on
the Sun through its propagation into the heliosphere
---------------------------------------------------------
Title: Analysing spectroscopically the propagation of a CME from
its source on the disk to its impact as it propagates outwards
Authors: Harra, Louise K.; Doschek, G. A.; Matthews, Sarah A.; De
Pontieu, Bart; Long, David
2014cosp...40E1159H Altcode:
We analyse a complex coronal mass ejection observed by Hinode, SDO and
IRIS. SDO AIA shows that the eruption occurs between several active
regions with flaring occurring in all of them. Hinode EIS observed one
of the flaring active regions that shows a fast outwards propagation
which is related to the CME lifting off. The eruption is then observed
as it propagates away from the Sun, pushing the existing post-flare
loops downwards as it goes. Spectroscopic observations are made during
this time with IRIS measuring the impact that this CME front has as
it pushes the loops downwards. Strong enhancements in the cool Mg II
emission at these locations that show complex dynamics. We discuss
these new observations in context of CME models.
---------------------------------------------------------
Title: Magnetic Polarity Streams and Subsurface Flows
Authors: Howe, R.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L.;
Komm, R.; Hill, F.; González Hernández, I.
2013ASPC..478..291H Altcode:
An important feature of the solar cycle is the transport of unbalanced
magnetic flux from active regions towards the poles, which eventually
results in polarity reversal. This transport takes the form of distinct
“polarity streams” that are visible in the magnetic butterfly
diagram. We compare the poleward migration rate estimated from such
streams to that derived from the subsurface meridional flows measured
in helioseismic data from the GONG network since 2001, and find that
the results are in reasonable agreement.
---------------------------------------------------------
Title: Measuring the Magnetic-Field Strength of the Quiet Solar
Corona Using "EIT Waves"
Authors: Long, D. M.; Williams, D. R.; Régnier, S.; Harra, L. K.
2013SoPh..288..567L Altcode: 2013arXiv1305.5169L
Variations in the propagation of globally propagating disturbances
(commonly called "EIT waves") through the low solar corona offer
a unique opportunity to probe the plasma parameters of the solar
atmosphere. Here, high-cadence observations of two "EIT wave" events
taken using the Atmospheric Imaging Assembly (AIA) instrument onboard
the Solar Dynamics Observatory (SDO) are combined with spectroscopic
measurements from the Extreme ultraviolet Imaging Spectrometer (EIS)
onboard the Hinode spacecraft and used to examine the variability of
the quiet coronal magnetic-field strength. The combination of pulse
kinematics from SDO/AIA and plasma density from Hinode/EIS is used
to show that the magnetic-field strength is in the range ≈ 2 - 6
G in the quiet corona. The magnetic-field estimates are then used to
determine the height of the pulse, allowing a direct comparison with
theoretical values obtained from magnetic-field measurements from the
Helioseismic and Magnetic Imager (HMI) onboard SDO using global-scale
PFSS and local-scale extrapolations. While local-scale extrapolations
predict heights inconsistent with prior measurements, the agreement
between observations and the PFSS model indicates that "EIT waves"
are a global phenomenon influenced by global-scale magnetic field.
---------------------------------------------------------
Title: Twisting solar coronal jet launched at the boundary of an
active region
Authors: Schmieder, B.; Guo, Y.; Moreno-Insertis, F.; Aulanier, G.;
Yelles Chaouche, L.; Nishizuka, N.; Harra, L. K.; Thalmann, J. K.;
Vargas Dominguez, S.; Liu, Y.
2013A&A...559A...1S Altcode: 2013arXiv1309.6514S
<BR /> Aims: A broad jet was observed in a weak magnetic field area
at the edge of active region NOAA 11106 that also produced other
nearby recurring and narrow jets. The peculiar shape and magnetic
environment of the broad jet raised the question of whether it was
created by the same physical processes of previously studied jets
with reconnection occurring high in the corona. <BR /> Methods:
We carried out a multi-wavelength analysis using the EUV images
from the Atmospheric Imaging Assembly (AIA) and magnetic fields
from the Helioseismic and Magnetic Imager (HMI) both on-board the
Solar Dynamics Observatory, which we coupled to a high-resolution,
nonlinear force-free field extrapolation. Local correlation tracking
was used to identify the photospheric motions that triggered the jet,
and time-slices were extracted along and across the jet to unveil its
complex nature. A topological analysis of the extrapolated field was
performed and was related to the observed features. <BR /> Results:
The jet consisted of many different threads that expanded in around 10
minutes to about 100 Mm in length, with the bright features in later
threads moving faster than in the early ones, reaching a maximum speed
of about 200 km s<SUP>-1</SUP>. Time-slice analysis revealed a striped
pattern of dark and bright strands propagating along the jet, along with
apparent damped oscillations across the jet. This is suggestive of a
(un)twisting motion in the jet, possibly an Alfvén wave. Bald patches
in field lines, low-altitude flux ropes, diverging flow patterns, and a
null point were identified at the basis of the jet. <BR /> Conclusions:
Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused
by reconnection in current sheets containing null points, reconnection
in regions containing bald patches seems to be crucial in triggering
the present jet. There is no observational evidence that the flux
ropes detected in the topological analysis were actually being ejected
themselves, as occurs in the violent phase of blowout jets; instead,
the jet itself may have gained the twist of the flux rope(s) through
reconnection. This event may represent a class of jets different from
the classical quiescent or blowout jets, but to reach that conclusion,
more observational and theoretical work is necessary.
---------------------------------------------------------
Title: Evidence for Hot Fast Flow above a Solar Flare Arcade
Authors: Imada, S.; Aoki, K.; Hara, H.; Watanabe, T.; Harra, L. K.;
Shimizu, T.
2013ApJ...776L..11I Altcode: 2013arXiv1309.3401I
Solar flares are one of the main forces behind space weather
events. However, the mechanism that drives such energetic phenomena is
not fully understood. The standard eruptive flare model predicts that
magnetic reconnection occurs high in the corona where hot fast flows are
created. Some imaging or spectroscopic observations have indicated the
presence of these hot fast flows, but there have been no spectroscopic
scanning observations to date to measure the two-dimensional structure
quantitatively. We analyzed a flare that occurred on the west solar
limb on 2012 January 27 observed by the Hinode EUV Imaging Spectrometer
(EIS) and found that the hot (~30MK) fast (>500 km s<SUP>-1</SUP>)
component was located above the flare loop. This is consistent with
magnetic reconnection taking place above the flare loop.
---------------------------------------------------------
Title: The Location of Non-thermal Velocity in the Early Phases of
Large Flares—Revealing Pre-eruption Flux Ropes
Authors: Harra, Louise K.; Matthews, Sarah; Culhane, J. L.; Cheung,
Mark C. M.; Kontar, Eduard P.; Hara, Hirohisa
2013ApJ...774..122H Altcode:
Non-thermal velocity measurements of the solar atmosphere, particularly
from UV and X-ray emission lines have demonstrated over the decades
that this parameter is important in understanding the triggering of
solar flares. Enhancements have often been observed before intensity
enhancements are seen. However, until the launch of Hinode, it has
been difficult to determine the spatial location of the enhancements to
better understand the source region. The Hinode EUV Imaging Spectrometer
has the spectral and spatial resolution to allow us to probe the early
stages of flares in detail. We analyze four events, all of which
are GOES M- or X-classification flares, and all are located toward
the limb for ease of flare geometry interpretation. Three of the
flares were eruptive and one was confined. In all events, pre-flare
enhancement in non-thermal velocity at the base of the active region
and its surroundings has been found. These enhancements seem to be
consistent with the footpoints of the dimming regions, and hence may
be highlighting the activation of a coronal flux rope for the three
eruptive events. In addition, pre-flare enhancements in non-thermal
velocity were found above the looptops for the three eruptive events.
---------------------------------------------------------
Title: Signatures of Slow Solar Wind Streams from Active Regions in
the Inner Corona
Authors: Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.;
Berghmans, D.
2013SoPh..286..157S Altcode: 2012arXiv1203.6756S; 2012SoPh..tmp..144S
The identification of solar-wind sources is an important question
in solar physics. The existing solar-wind models (e.g., the
Wang-Sheeley-Arge model) provide the approximate locations of the
solar wind sources based on magnetic field extrapolations. It has been
suggested recently that plasma outflows observed at the edges of active
regions may be a source of the slow solar wind. To explore this we
analyze an isolated active region (AR) adjacent to small coronal hole
(CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer
observations showed two compact outflow regions in the corona. Coronal
rays were observed above the active-region coronal hole (ARCH) region
on the eastern limb on 31 July by STEREO-A/EUVI and at the western
limb on 7 August by CORONAS-Photon/TESIS telescopes. In both cases
the coronal rays were co-aligned with open magnetic-field lines given
by the potential field source surface model, which expanded into the
streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind,
and STEREO-A confirmed the identification of the ARCH as a source
region of the slow solar wind. The results of the study support the
suggestion that coronal rays can represent signatures of outflows
from ARs propagating in the inner corona along open field lines into
the heliosphere.
---------------------------------------------------------
Title: Are subsurface flows and coronal holes related?
Authors: Komm, R.; Howe, R.; González Hernández, I.; Harra, L.;
Baker, D.; van Driel-Gesztelyi, L.
2013JPhCS.440a2022K Altcode:
We study synoptic maps of solar subsurface flows covering six Carrington
rotations (2050 to 2055). The subsurface flows are determined with
a ring-diagram analysis of GONG high-resolution Doppler data. We
identify the locations of coronal holes in synoptic maps of EUV images
at 195Å from the EIT instrument and determine the characteristics
of associated subsurface flows. We study two long-lived coronal holes
that are present during this epoch. We find that large-scale patterns
are present in the subsurface flows but appear to be unrelated to
these coronal holes. The horizontal subsurface flows associated with
the two long-lived coronal holes are weakly divergent (upflows) with
small cyclonic vorticity. These flows are thus similar to subsurface
flows of quiet regions with regard to the vertical flows and similar
to flows of active regions with regard to vorticity.
---------------------------------------------------------
Title: Can we detect local helioseismic parameter shifts in coronal
holes?
Authors: Howe, R.; Haber, D. A.; Bogart, R. S.; Zharkov, S.; Baker,
D.; Harra, L.; van Driel-Gesztelyi, L.
2013JPhCS.440a2019H Altcode:
Changes in helioseismic mode parameters in active regions and across
the solar disk are well documented, but local magnetic activity
and geometric effects may not account for all of the scatter seen
in the results. We use results from the Helioseismic and Magnetic
Imager ring-diagram pipeline for Carrington rotation 2113 to look for
differences in mode amplitude and frequency between coronal holes and
other quiet-Sun regions. While we do not find a systematic difference,
the results do suggest that the correlation between magnetic activity
index and mode parameters shows less scatter in coronal hole regions
than in general quiet Sun.
---------------------------------------------------------
Title: Subsurface flows associated with non-Joy oriented active
regions: a case study
Authors: González Hernández, Irene; Komm, Rudolf; van
Driel-Gesztelyi, Lidia; Baker, Deborah; Harra, Louise; Howe, Rachel
2013JPhCS.440a2050G Altcode:
Non-Joy oriented active regions (ARs) are a challenge for solar magnetic
field modelers. Although significant deviations from Joy's law are
relatively rare for simple bipolar ARs, understanding the causes of
their particularity could be critical for the big picture of the solar
dynamo. We explore the possibility of the sub-surface local dynamics
being responsible for the significant rotation of these ARs. We apply
the ring-diagram technique, a local helioseismology method, to infer
the flows under and surrounding a non-Joy oriented AR and present the
results of a case study in this paper.
---------------------------------------------------------
Title: Measuring the magnetic field strength of the quiet solar
corona using "EIT waves"
Authors: Long, David M.; Williams, David R.; Régnier, Stéphane;
Harra, Louise K.
2013enss.confE..89L Altcode:
Variations in the propagation of globally-propagating disturbances
(commonly called "EIT waves") through the low solar corona offer
a unique opportunity to probe the plasma parameters of the solar
atmosphere. Here, high-cadence observations of two "EIT wave" events
taken using SDO/AIA are combined with spectroscopic measurements from
Hinode/EIS and used to examine the variability of the quiet coronal
magnetic field strength. The combination of pulse kinematics from AIA
and plasma density from EIS is used to show that the magnetic field
strength is in the range 2-6G in the quiet corona. The magnetic field
estimates are then used to determine the height of the pulse, allowing
a direct comparison with theoretical values obtained from SDO/HMI
magnetic field using PFSS and local-domain extrapolations. While
local-scale extrapolations predict heights inconsistent with prior
measurements, the agreement between observations and the PFSS model
indicates that "EIT waves" are a global phenomenon influenced by
global-scale magnetic field.
---------------------------------------------------------
Title: Production of High-Temperature Plasmas During the Early Phases
of a C9.7 Flare. II. Bi-directional Flows Suggestive of Reconnection
in a Pre-flare Brightening Region
Authors: Watanabe, T.; Hara, H.; Sterling, A. C.; Harra, L. K.
2012SoPh..281...87W Altcode: 2012SoPh..tmp..185W
The 6 June 2007 16:55 UT flare was well observed with high time-cadence
sparse raster scans by the EUV Imaging Spectrometer (EIS) on board
the Hinode spacecraft. The observation covers an active region area
of 240 arcsec × 240 arcsec with the 1 arcsec slit in about 160 seconds.
---------------------------------------------------------
Title: Non-thermal Response of the Corona to the Magnetic Flux
Dispersal in the Photosphere of a Decaying Active Region
Authors: Harra, L. K.; Abramenko, V. I.
2012ApJ...759..104H Altcode:
We analyzed Solar Dynamics Observatory line-of-sight magnetograms
for a decaying NOAA active region (AR) 11451 along with co-temporal
Extreme-Ultraviolet Imaging Spectrometer (EIS) data from the Hinode
spacecraft. The photosphere was studied via time variations of the
turbulent magnetic diffusivity coefficient, η(t), and the magnetic
power spectrum index, α, through analysis of magnetogram data from the
Helioseismic and Magnetic Imager (HMI). These measure the intensity of
the random motions of magnetic elements and the state of turbulence of
the magnetic field, respectively. The time changes of the non-thermal
energy release in the corona was explored via histogram analysis of
the non-thermal velocity, v <SUB>nt</SUB>, in order to highlight the
largest values at each time, which may indicate an increase in energy
release in the corona. We used the 10% upper range of the histogram
of v <SUB>nt</SUB> (which we called V <SUP>upp</SUP> <SUB>nt</SUB>)
of the coronal spectral line of Fe XII 195 Å. A 2 day time interval
was analyzed from HMI data, along with the EIS data for the same
field of view. Our main findings are the following. (1) The magnetic
turbulent diffusion coefficient, η(t), precedes the upper range of
the v <SUB>nt</SUB> with the time lag of approximately 2 hr and the
cross-correlation coefficient of 0.76. (2) The power-law index, α, of
the magnetic power spectrum precedes V <SUP>upp</SUP> <SUB>nt</SUB>
with a time lag of approximately 3 hr and the cross-correlation
coefficient of 0.5. The data show that the magnetic flux dispersal in
the photosphere is relevant to non-thermal energy release dynamics
in the above corona. The results are consistent with the nanoflare
mechanism of the coronal heating, due to the time lags being consistent
with the process of heating and cooling the loops heated by nanoflares.
---------------------------------------------------------
Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1” and 0.3”), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280” on the Sun with
0.14” per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s<SUP> - 1</SUP> or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
---------------------------------------------------------
Title: The EUI instrument on board the Solar Orbiter mission: from
breadboard and prototypes to instrument model validation
Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.;
Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.;
Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.;
Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P.
2012SPIE.8443E..07H Altcode:
The Solar Orbiter mission will explore the connection between the Sun
and its heliosphere, taking advantage of an orbit approaching the Sun at
0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI)
will provide full-sun and high-resolution image sequences of the solar
atmosphere at selected spectral emission lines in the extreme and vacuum
ultraviolet. To achieve the required scientific performances under the
challenging constraints of the Solar Orbiter mission it was required
to further develop existing technologies. As part of this development,
and of its maturation of technology readiness, a set of breadboard and
prototypes of critical subsystems have thus been realized to improve
the overall instrument design. The EUI instrument architecture, its
major components and sub-systems are described with their driving
constraints and the expected performances based on the breadboard and
prototype results. The instrument verification and qualification plan
will also be discussed. We present the thermal and mechanical model
validation, the instrument test campaign with the structural-thermal
model (STM), followed by the other instrument models in advance of
the flight instrument manufacturing and AIT campaign.
---------------------------------------------------------
Title: The Slow Solar Wind: From Formation on the Sun to the Earth
Authors: Harra, L. K.; Fazakerley, A. N.; van Driel-Gesztelyi, L.
2012ASPC..454..421H Altcode:
Hinode has discovered a potential source of slow solar wind at the
edges of active regions with the X-ray Telescope (XRT) and EUV Imaging
spectrometer (EIS) on board Hinode e.g. Sakao et al. (2007), Harra
et al. (2008), Doschek et al. (2008). These upflows are long-lasting
and exist at the edges of most active regions. In this conference
paper we first discuss the onset of the upflows. This is related to
newly emerged magnetic flux into an active region. Next we discuss
whether the flows that we see on the surface of the Sun actually are
transported to the Earth in the slow solar wind. To do this we looked at
a number of different examples over a Carrington rotation and tracked
the response in the solar wind as measured by the ACE spacecraft at
L1. We found that there is a significant enhancement of the in situ
solar wind speed for active regions located close to a coronal hole.
---------------------------------------------------------
Title: Helioseismic Investigation of Sub-Photospheric Properties of
a Coronal Hole
Authors: Zharkov, S.; Harra, L. K.; Sekii, T.
2012ASPC..454...27Z Altcode:
We present initial results of our investigation into sub-photospheric
properties of an equatorial coronal hole obtained via helioseismic
analysis using Hinode and MDI observational data. As at photospheric
level coronal holes are characterised by open magnetic field we look
for seismic signatures of such fields and compare those to the ones
observed in plages.
---------------------------------------------------------
Title: Are subsurface flows and coronal holes related?
Authors: Komm, Rudolf W.; Howe, R.; González Hernández, I.; Harra,
L.; Baker, D.; van Driel-Gesztelyi, L.
2012shin.confE.120K Altcode:
We study subsurface flows measured with a ring-diagram analysis of GONG
high-resolution Doppler data. In previous studies, we have focused on
the relationship between active regions and subsurface flows associated
with them. Synoptic subsurface flow maps show also large-scale patterns
that are not obviously associated with active regions. It is unknown
whether these flow patterns correlate with any large-scale magnetic
features. Here, we explore whether there is a relationship between
subsurface flows and coronal features. We analyze synoptic maps of
subsurface flows covering 18 Carrington rotations during the years
2006 and 2007 (CR 2038-2055). Long-lived coronal holes are present
during this epoch at low latitudes, which are accessible by ring-diagram
analysis of GONG data. We compare subsurface flow maps with EIT synoptic
maps of EUV images at 195A (http://sun.stanford.edu/synop/EIT/) and
will present the latest results.
---------------------------------------------------------
Title: The Creation of Outflowing Plasma in the Corona at Emerging
Flux Regions: Comparing Observations and Simulations
Authors: Harra, L. K.; Archontis, V.; Pedram, E.; Hood, A. W.; Shelton,
D. L.; van Driel-Gesztelyi, L.
2012SoPh..278...47H Altcode:
In this paper we analyse the flux emergence that occurred in the
following polarity area of an active region on 1 - 2 December
2006. Observations have revealed the existence of fast outflows
at the edge of the emerging flux region. We have performed 3-D
numerical simulations to study the mechanisms responsible for these
flows. The results indicate that these outflows are reconnection jets
or pressure-driven outflows, depending on the relative orientation
of the magnetic fields in contact (i.e. the emerging flux and the
active region's field which is favourable for reconnection on the
west side and nearly parallel with the pre-existing field on the east
side of the emerging flux). In the observations, the flows are larger
on the west side until late in the flux emergence, when the reverse
is true. The simulations show that the flows are faster on the west
side, but do not show the east flows increasing with time. There is an
asymmetry in the expansion of the emerging flux region, which is also
seen in the observations. The west side of the emerging flux region
expands faster into the corona than the other side. In the simulations,
efficient magnetic reconnection occurs on the west side, with new loops
being created containing strong downflows that are clearly seen in the
observations. On the other side, the simulations show strong compression
as the dominant mechanism for the generation of flows. There is evidence
of these flows in the observations, but the flows are stronger than
the simulations predict at the later stages. There could be additional
small-angle reconnection that adds to the flows from the compression,
as well as reconnection occurring in larger loops that lie across the
whole active region.
---------------------------------------------------------
Title: The Role of Coronal Hole and Active Region Boundaries in
Solar Wind Formation
Authors: Harra, L. K.
2012ASPC..455..315H Altcode: 2012arXiv1201.4646H
Hinode observations have provided a new view of outflows from the
Sun. These have been focussed in particular on flows emanating from
the edges of active regions. These flows are long lasting and seem
to exist to some extent in every active region. The flows measured
have values ranging between tens of km s<SUP>-1</SUP> and 200 km
s<SUP>-1</SUP>. Various explanations have been put forward to explain
these flows including reconnection, waves, and compression. Outflows
have also been observed in coronal holes and this review will
discuss those as well as the interaction of coronal holes with active
regions. Although outflowing plasma has been observed in all regions
of the Sun from quiet Sun to active regions, it is not clear how
much of this plasma contributes to the solar wind. I will discuss
various attempts to prove that the outflowing plasma forms part of
the solar wind.
---------------------------------------------------------
Title: Flare-associated Energy Exchange Between the Photosphere
and Corona
Authors: Abramenko, Valentyna; Harra, L.
2012AAS...22020414A Altcode:
In recent decades, it has been clearly demonstrated that strong
flares in ARs (referred before as chromospheric flares) are not
restricted to some closed volume in the chromosphere but rather
involve a huge volume from deep sub-photospheric layers to the
outer heliosphere. Undoubtedly, there exists interaction and energy
exchange between different parts of the volume occupied by a flare,
e.g., reconnection between up-welling loops and the pre-existing flux,
waves and shocks, seismic response to a flare, momentum distribution and
Lorentz Force acting, accelerated particle, heat, X-ray propagation,
Poynting flux transport, etc. However, mechanisms of the processes,
as well as their relationship with the flare itself (is a phenomenon
a prelude to the flare, its consequence or non of such) is not well
understood yet. We explore new metrics of the photospheric magnetic
field: we monitor the magnetic energy dissipation rate. For three
strong flares, we found that the magnetic energy dissipation rate sets
to a monotonous ceasing several hours before the flare onset. Assuming
nearly gradual energy input, the reduction of the energy dissipation
rate implies that somewhere in the active region, the energy is being
accumulated. The non-dissipated and accumulated energy amounts to (3 -
10) x 10<SUP>32</SUP> ergs. We presume that at least part of the energy
accumulated immediately before the flare is transferred into the corona
and further drives the corona to a trigger point when flare occurs.
---------------------------------------------------------
Title: One-dimensional Modeling for Temperature-dependent Upflow in
the Dimming Region Observed by Hinode/EUV Imaging Spectrometer
Authors: Imada, S.; Hara, H.; Watanabe, T.; Murakami, I.; Harra,
L. K.; Shimizu, T.; Zweibel, E. G.
2011ApJ...743...57I Altcode: 2011arXiv1108.5031I
We previously found a temperature-dependent upflow in the dimming region
following a coronal mass ejection observed by the Hinode EUV Imaging
Spectrometer (EIS). In this paper, we reanalyzed the observations along
with previous work on this event and provided boundary conditions for
modeling. We found that the intensity in the dimming region dramatically
drops within 30 minutes from the flare onset, and the dimming region
reaches the equilibrium stage after ~1 hr. The temperature-dependent
upflows were observed during the equilibrium stage by EIS. The
cross-sectional area of the flux tube in the dimming region does not
appear to expand significantly. From the observational constraints,
we reconstructed the temperature-dependent upflow by using a new method
that considers the mass and momentum conservation law and demonstrated
the height variation of plasma conditions in the dimming region. We
found that a super-radial expansion of the cross-sectional area is
required to satisfy the mass conservation and momentum equations. There
is a steep temperature and velocity gradient of around 7 Mm from
the solar surface. This result may suggest that the strong heating
occurred above 7 Mm from the solar surface in the dimming region. We
also showed that the ionization equilibrium assumption in the dimming
region is violated, especially in the higher temperature range.
---------------------------------------------------------
Title: Lateral Offset of the Coronal Mass Ejections from the X-flare
of 2006 December 13 and Its Two Precursor Eruptions
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Harra, Louise K.
2011ApJ...743...63S Altcode:
Two GOES sub-C-class precursor eruptions occurred within ~10 hr prior
to and from the same active region as the 2006 December 13 X4.3-class
flare. Each eruption generated a coronal mass ejection (CME) with
center laterally far offset (gsim 45°) from the co-produced bright
flare. Explaining such CME-to-flare lateral offsets in terms of the
standard model for solar eruptions has been controversial. Using
Hinode/X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS)
data, and Solar and Heliospheric Observatory (SOHO)/Large Angle and
Spectrometric Coronagraph (LASCO) and Michelson Doppler Imager (MDI)
data, we find or infer the following. (1) The first precursor was a
"magnetic-arch-blowout" event, where an initial standard-model eruption
of the active region's core field blew out a lobe on one side of the
active region's field. (2) The second precursor began similarly, but the
core-field eruption stalled in the side-lobe field, with the side-lobe
field erupting ~1 hr later to make the CME either by finally being blown
out or by destabilizing and undergoing a standard-model eruption. (3)
The third eruption, the X-flare event, blew out side lobes on both
sides of the active region and clearly displayed characteristics of the
standard model. (4) The two precursors were offset due in part to the
CME originating from a side-lobe coronal arcade that was offset from
the active region's core. The main eruption (and to some extent probably
the precursor eruptions) was offset primarily because it pushed against
the field of the large sunspot as it escaped outward. (5) All three CMEs
were plausibly produced by a suitable version of the standard model.
---------------------------------------------------------
Title: Plasma Motions and Heating by Magnetic Reconnection in a 2007
May 19 Flare
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.
2011ApJ...741..107H Altcode:
Based on scanning spectroscopic observations with the Hinode EUV
imaging spectrometer, we have found a loop-top hot source, a fast
jet nearby, and an inflow structure flowing to the hot source that
appeared in the impulsive phase of a long-duration flare at the
disk center on 2007 May 19. The hot source observed in Fe XXIII and
Fe XXIV emission lines has the electron temperature of 12 MK and
density of 1 × 10<SUP>10</SUP> cm<SUP>-3</SUP>. It shows excess
line broadening, which exceeds the thermal Doppler width by ~100 km
s<SUP>-1</SUP>, with a weak redshift of ~30 km s<SUP>-1</SUP>. We have
also observed a blueshifted faint jet whose Doppler velocity exceeds
200 km s<SUP>-1</SUP> with an electron temperature of 9 MK. Coronal
plasmas with electron temperature of 1.2 MK and density of 2.5 ×
10<SUP>9</SUP> cm<SUP>-3</SUP> that flow into the loop-top region
with a Doppler velocity of 20 km s<SUP>-1</SUP> have been identified
in the Fe XII observation. They disappeared near the hot source,
possibly by being heated to the hotter faint jet temperature. From
the geometrical relationships of these phenomena, we conclude that
they provide evidence for magnetic reconnection that occurs near the
loop-top region. The estimated reconnection rate is 0.05-0.1, which
supports the Petschek-type magnetic reconnection. Further supporting
evidence for the presence of the slow-mode and fast-mode MHD shocks
in the reconnection geometry is given based on the observed quantities.
---------------------------------------------------------
Title: LEMUR (Large European Module for solar Ultraviolet Research):
a VUV imaging spectrograph for the JAXA Solar-C Mission
Authors: Korendyke, Clarence M.; Teriaca, Luca; Doschek, George A.;
Harra, Louise K.; Schühle, Udo H.; Shimizu, Toshifumi
2011SPIE.8148E..0IK Altcode: 2011SPIE.8148E..17K
LEMUR is a VUV imaging spectrograph with 0.28" resolution. Incident
solar radiation is imaged onto the spectrograph slit by a single
mirror telescope consisting of a 30-cm steerable f/12 off-axis
paraboloid mirror. The spectrograph slit is imaged and dispersed by
a highly corrected grating that focuses the solar spectrum over the
detectors. The mirror is coated with a suitable multilayer with B4C
top-coating providing a reflectance peak around 18.5 nm besides the
usual B4C range above 500Å. The grating is formed by two halves, one
optimized for performances around 185Å and the other above 500Å. Three
intensified CCD cameras will record spectra above 50 nm while a large
format CCD array with an aluminum filter will be used around 185Å.
---------------------------------------------------------
Title: Spectroscopic Analysis of Interaction between an
Extreme-ultraviolet Imaging Telescope Wave and a Coronal Upflow Region
Authors: Chen, F.; Ding, M. D.; Chen, P. F.; Harra, L. K.
2011ApJ...740..116C Altcode: 2011arXiv1107.5630C
We report a spectroscopic analysis of an EUV Imaging Telescope (EIT)
wave event that occurred in active region 11081 on 2010 June 12 and
was associated with an M2.0 class flare. The wave propagated nearly
circularly. The southeastern part of the wave front passed over an
upflow region near a magnetic bipole. Using EUV Imaging Spectrometer
raster observations for this region, we studied the properties of
plasma dynamics in the wave front, as well as the interaction between
the wave and the upflow region. We found a weak blueshift for the
Fe XII λ195.12 and Fe XIII λ202.04 lines in the wave front. The
local velocity along the solar surface, which is deduced from the
line-of-sight velocity in the wave front and the projection effect,
is much lower than the typical propagation speed of the wave. A more
interesting finding is that the upflow and non-thermal velocities
in the upflow region are suddenly diminished after the transit of
the wave front. This implies a significant change of magnetic field
orientation when the wave passed. As the lines in the upflow region
are redirected, the velocity along the line of sight is diminished
as a result. We suggest that this scenario is more in accordance with
what was proposed in the field-line stretching model of EIT waves.
---------------------------------------------------------
Title: Spectroscopic Observations of a Coronal Moreton Wave
Authors: Harra, Louise K.; Sterling, Alphonse C.; Gömöry, Peter;
Veronig, Astrid
2011ApJ...737L...4H Altcode:
We observed a coronal wave (EIT wave) on 2011 February 16, using
EUV imaging data from the Solar Dynamics Observatory/Atmospheric
Imaging Assembly (AIA) and EUV spectral data from the Hinode/EUV
Imaging Spectrometer (EIS). The wave accompanied an M1.6 flare that
produced a surge and a coronal mass ejection (CME). EIS data of the
wave show a prominent redshifted signature indicating line-of-sight
velocities of ~20 km s<SUP>-1</SUP> or greater. Following the main
redshifted wave front, there is a low-velocity period (and perhaps
slightly blueshifted), followed by a second redshift somewhat weaker
than the first; this progression may be due to oscillations of the EUV
atmosphere set in motion by the initial wave front, although alternative
explanations may be possible. Along the direction of the EIS slit the
wave front's velocity was ~500 km s<SUP>-1</SUP>, consistent with
its apparent propagation velocity projected against the solar disk
as measured in the AIA images, and the second redshifted feature had
propagation velocities between ~200 and 500 km s<SUP>-1</SUP>. These
findings are consistent with the observed wave being generated by the
outgoing CME, as in the scenario for the classic Moreton wave. This
type of detailed spectral study of coronal waves has hitherto been a
challenge, but is now possible due to the availability of concurrent
AIA and EIS data.
---------------------------------------------------------
Title: Determining the Solar Source of a Magnetic Cloud Using a
Velocity Difference Technique
Authors: Harra, L. K.; Mandrini, C. H.; Dasso, S.; Gulisano, A. M.;
Steed, K.; Imada, S.
2011SoPh..268..213H Altcode: 2010SoPh..tmp..210H; 2010SoPh..tmp..234H
For large eruptions on the Sun, it is often a problem that the core
dimming region cannot be observed due to the bright emission from the
flare itself. However, spectroscopic data can provide the missing
information through the measurement of Doppler velocities. In this
paper we analyse the well-studied flare and coronal mass ejection
that erupted on the Sun on 13 December 2006 and reached the Earth on
14 December 2006. In this example, although the imaging data were
saturated at the flare site itself, by using velocity measurements
we could extract information on the core dimming region, as well as
on remote dimmings. The purpose of this paper is to determine more
accurately the magnetic flux of the solar source region, potentially
involved in the ejection, through a new technique. The results of its
application are compared to the flux in the magnetic cloud observed at
1 AU, as a way to check the reliability of this technique. We analysed
data from the Hinode EUV Imaging Spectrometer to estimate the Doppler
velocity in the active region and its surroundings before and after
the event. This allowed us to determine a Doppler velocity `difference'
image. We used the velocity difference image overlayed on a Michelson
Doppler Imager magnetogram to identify the regions in which the blue
shifts were more prominent after the event; the magnetic flux in these
regions was used as a proxy for the ejected flux and compared to the
magnetic cloud flux. This new method provides a more accurate flux
determination in the solar source region.
---------------------------------------------------------
Title: Pre-Flare Flows in the Corona
Authors: Wallace, A. J.; Harra, L. K.; van Driel-Gesztelyi, L.; Green,
L. M.; Matthews, S. A.
2010SoPh..267..361W Altcode: 2010SoPh..tmp..223W; 2010SoPh..tmp..199W
Solar flares take place in regions of strong magnetic fields and
are generally accepted to be the result of a resistive instability
leading to magnetic reconnection. When new flux emerges into a
pre-existing active region it can act as a flare and coronal mass
ejection trigger. In this study we observed active region 10955 after
the emergence of small-scale additional flux at the magnetic inversion
line. We found that flaring began when additional positive flux levels
exceeded 1.38×10<SUP>20</SUP> Mx (maxwell), approximately 7 h after
the initial flux emergence. We focussed on the pre-flare activity of
one B-class flare that occurred on the following day. The earliest
indication of activity was a rise in the non-thermal velocity one
hour before the flare. 40 min before flaring began, brightenings and
pre-flare flows were observed along two loop systems in the corona,
involving the new flux and the pre-existing active region loops. We
discuss the possibility that reconnection between the new flux
and pre-existing loops before the flare drives the flows by either
generating slow mode magnetoacoustic waves or a pressure gradient
between the newly reconnected loops. The subsequent B-class flare
originated from fast reconnection of the same loop systems as the
pre-flare flows.
---------------------------------------------------------
Title: Fibrillar Chromospheric Spicule-like Counterparts to an
Extreme-ultraviolet and Soft X-ray Blowout Coronal Jet
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.
2010ApJ...722.1644S Altcode:
We observe an erupting jet feature in a solar polar coronal hole, using
data from Hinode/Solar Optical Telescope (SOT), Extreme Ultraviolet
Imaging Spectrometer (EIS), and X-Ray Telescope (XRT), with supplemental
data from STEREO/EUVI. From extreme-ultraviolet (EUV) and soft X-ray
(SXR) images we identify the erupting feature as a blowout coronal
jet: in SXRs it is a jet with a bright base, and in EUV it appears
as an eruption of relatively cool (~50,000 K) material of horizontal
size scale ~30” originating from the base of the SXR jet. In SOT
Ca II H images, the most pronounced analog is a pair of thin (~1”)
ejections at the locations of either of the two legs of the erupting
EUV jet. These Ca II features eventually rise beyond 45”, leaving the
SOT field of view, and have an appearance similar to standard spicules
except that they are much taller. They have velocities similar to that
of "type II" spicules, ~100 km s<SUP>-1</SUP>, and they appear to have
spicule-like substructures splitting off from them with horizontal
velocity ~50 km s<SUP>-1</SUP>, similar to the velocities of splitting
spicules measured by Sterling et al. Motions of splitting features and
of other substructures suggest that the macroscopic EUV jet is spinning
or unwinding as it is ejected. This and earlier work suggest that a
subpopulation of Ca II type II spicules are the Ca II manifestation
of portions of larger scale erupting magnetic jets. A different
subpopulation of type II spicules could be blowout jets occurring on
a much smaller horizontal size scale than the event we observe here.
---------------------------------------------------------
Title: Production of High-temperature Plasmas During the Early Phases
of a C9.7 Flare
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Sterling, Alphonse C.;
Harra, Louise K.
2010ApJ...719..213W Altcode:
Explosive chromospheric evaporation is predicted from some current
solar flare models. In this paper, we analyze a flare with high time
cadence raster scans with the EUV Imaging Spectrometer (EIS) on board
the Hinode spacecraft. This observation covers an area of 240” ×
240”, with the 1” slit in about 160 s. The early phases of a C9.7
flare that occurred on 2007 June 6 were well observed. The purpose of
our analysis is to study for the first time the spatially resolved
spectra of high-temperature plasma, especially from Fe XXIII and Fe
XXIV, allowing us to explore the explosive chromospheric evaporation
scenario further. Sections of raster images obtained between 17:20:09
and 17:20:29 (UT) show a few bright patches of emission from Fe
XXIII/Fe XXIV lines at the footpoints of the flaring loops; these
footpoints were not clearly seen in the images taken earlier, between
17:17:30 and 17:17:49 (UT). Fe XXIII spectra at these footpoints show
dominating blueshifted components of -(300 to 400) km s<SUP>-1</SUP>,
while Fe XV/XIV lines are nearly stationary; Fe XII lines and/or
lower temperature lines show slightly redshifted features, and Fe
VIII and Si VII to He II lines show ~+50 km s<SUP>-1</SUP> redshifted
components. The density of the 1.5-2 MK plasma at these footpoints is
estimated to be 3 × 10<SUP>10</SUP> cm<SUP>-3</SUP> by the Fe XIII/XIV
line pairs around the maximum of the flare. High-temperature loops
connecting the footpoints appear in the Fe XXIII/XXIV images taken over
17:22:49-17:23:08 (UT) which is near the flare peak. Line profiles of
these high-temperature lines at this flare peak time show only slowly
moving components. The concurrent cooler Fe XVII line at 254.8 Å is
relatively weak, indicating the predominance of high-temperature plasma
(>10<SUP>7</SUP> K) in these loops. The characteristics observed
during the early phases of this flare are consistent with the scenario
of explosive chromospheric evaporation.
---------------------------------------------------------
Title: The technical challenges of the Solar-Orbiter EUI instrument
Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry;
Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric;
Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence;
Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François;
Ben Moussa, Ali
2010SPIE.7732E..0RH Altcode: 2010SPIE.7732E..20H
The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of
a suite of two high-resolution imagers (HRI) and one dual-band full
Sun imager (FSI) that will provide EUV and Lyman-α images of the
solar atmospheric layers above the photosphere. The EUI instrument is
based on a set of challenging new technologies allowing to reach the
scientific objectives and to cope with the hard space environment of
the Solar Orbiter mission. The mechanical concept of the EUI instrument
is based on a common structure supporting the HRI and FSI channels,
and a separated electronic box. A heat rejection baffle system is
used to reduce the Sun heat load and provide a first protection level
against the solar disk straylight. The spectral bands are selected by
thin filters and multilayer mirror coatings. The detectors are 10μm
pitch back illuminated CMOS Active Pixel Sensors (APS), best suited
for the EUI science requirements and radiation hardness. This paper
presents the EUI instrument concept and its major sub-systems. The
current developments of the instrument technologies are also summarized.
---------------------------------------------------------
Title: Revealing the Fine Structure of Coronal Dimmings and Associated
Flows with Hinode/EIS. Implications for Understanding the Source
Regions of Sustained Outflow Following CMEs
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
Wills-Davey, M. J.
2010SoPh..264..119A Altcode: 2010SoPh..tmp...80A
We study two CME events on 13 and 14 December 2006 that were associated
with large-scale dimmings. We study the eruptions from pre-event on
11 December through the recovery on 15 December, using a combination
of Hinode/EIS, SOHO/EIT, SOHO/MDI, and MLSO Hα data. The GOES
X-class flares obscured the core dimmings, but secondary dimmings
developed remote from the active region (AR) in both events. The
secondary dimmings are found to be formed by a removal of bright
coronal material from loops in the plage region to the East of the
AR. Using Hinode/EIS data, we find that the outflows associated with
the coronal-dimming regions are highly structured. The concentrated
outflows are located at the footpoints of coronal loops (which exist
before, and are re-established after, the eruptions), and these are
correlated with regions of positive magnetic elements. Comparative
study of the Hinode/EIS and SOHO/EIT data shows that the reduction in
outflow velocity is consistent with the recovery in intensity of the
studied regions. We find that concentrated downflows develop during the
recovery phase of the dimmings and are also correlated with the same
positive magnetic elements that were previously related to outflows.
---------------------------------------------------------
Title: Response of the Solar Atmosphere to the Emergence of
`Serpentine' Magnetic Field
Authors: Harra, L. K.; Magara, T.; Hara, H.; Tsuneta, S.; Okamoto,
T. J.; Wallace, A. J.
2010SoPh..263..105H Altcode:
Active region magnetic flux that emerges to the photosphere from
below will show complexity in the structure, with many small-scale
fragmented features appearing in between the main bipole and then
disappearing. Some fragments seen will be absorbed into the main
polarities and others seem to cancel with opposite magnetic field. In
this paper we investigate the response of the corona to the behaviour
of these small fragments and whether energy through reconnection
will be transported into the corona. In order to investigate this we
analyse data from the Hinode space mission during flux emergence on
1 - 2 December 2006. At the initial stages of flux emergence several
small-scale enhancements (of only a few pixels size) are seen in the
coronal line widths and diffuse coronal emission exists. The magnetic
flux emerges as a fragmented structure, and coronal loops appear
above these structures or close to them. These loops are large-scale
structures - most small-scale features predominantly stay within the
chromosphere or at the edges of the flux emergence. The most distinctive
feature in the Doppler velocity is a strong ring of coronal outflows
around the edge of the emerging flux region on the eastern side which
is either due to reconnection or compression of the structure. This
feature lasts for many hours and is seen in many wavelengths. We
discuss the implications of this feature in terms of the onset of
persistent outflows from an active region that could contribute to
the slow solar wind.
---------------------------------------------------------
Title: Bright Points and Jets in Polar Coronal Holes Observed by
the Extreme-Ultraviolet Imaging Spectrometer on Hinode
Authors: Doschek, G. A.; Landi, E.; Warren, H. P.; Harra, L. K.
2010ApJ...710.1806D Altcode:
We present observations of polar coronal hole bright points (BPs)
made with the Extreme-ultraviolet Imaging Spectrometer (EIS) on the
Hinode spacecraft. The data consist of raster images of BPs in multiple
spectral lines from mostly coronal ions, e.g., Fe X-Fe XV. The BPs
are observed for short intervals and thus the data are snapshots of
the BPs obtained during their evolution. The images reveal a complex
unresolved temperature structure (EIS resolution is about 2”), with the
highest temperature being about 2 × 10<SUP>6</SUP> K. Some BPs appear
as small loops with temperatures that are highest near the top. But
others are more point-like with surrounding structures. However, the
thermal time evolution of the BPs is an important factor in their
appearance. A BP may appear quite different at different times. We
discuss one BP with an associated jet that is bright enough to allow
statistically meaningful measurements. The jet Doppler speed along the
line of sight is about 15-20 km s<SUP>-1</SUP>. Electron densities of
the BPs and the jet are typically near 10<SUP>9</SUP> cm<SUP>-3</SUP>,
which implies path lengths along the line of sight on the order of a
few arcsec. We also construct differential emission measure curves for
two of the best observed BPs. High spatial resolution (significantly
better than 1”) is required to fully resolve the BP structures.
---------------------------------------------------------
Title: An overview of the solar corona during the recent solar
minimum and prospective for the new cycle
Authors: Harra, Louise K.
2010cosp...38.4153H Altcode: 2010cosp.meet.4153H
The current solar minimum has been the deepest since the space age
began. This has provided us with an ideal opportunity to observe
the solar corona in different conditions with high accuracy
instrumentation. The Sun's polar fields are weaker than during
previous minimum, and have shrunk in size significantly. The number
of sunspots reached their lowest for 75 years with many more spotless
days occurring. Equatorial coronal holes were longer lasting during
this minimum, some lasting more than 20 rotations. The corona itself
during eclipses in the current solar minimum did not appear as a
'classic' dipole as previously was the case. I shall discuss these
various observational characteristics and describe how activity is
starting to increase.
---------------------------------------------------------
Title: What Coronal Dimming Regions tell us about CMEs? New Results
from Hinode
Authors: Harra, Louise K.
2010cosp...38.1858H Altcode: 2010cosp.meet.1858H
Coronal dimming has been a signature used to determine the source
of plasma that forms part of a coronal mass ejection (CME) for many
years. Generally dimming is detected through imaging instruments
by taking difference images. I discuss in this review spectroscopic
measurements made using the EUV Imaging Spectrometer (EIS) onboard
Hinode of dimming regions during flares in December 2006. In these
cases the velocity measurements allow us to determine the highest flow
regions, as well as determine 'dimming' regions within the flare site
itself which is often saturated in imaging data. This new method of
velocity differencing will allow a new perspective on the dimming
mechanism. The dimming recovery is also tracked with spectroscopic
data. I will also discuss events from the recent surge of solar
activity.
---------------------------------------------------------
Title: Reviewing UK space exploration
Authors: Curtis, Jeremy; Harra, Louise; Zarnecki, John; Grady, Monica
2010SpPol..26..113C Altcode:
This is an edited version of the Executive Summary of a report produced
to advise government ministers on the options for UK involvement in
space exploration. It sets out four options - from reduced involvement
through robotic-only to a fully integrated human and robotic involvement
- and discusses the economic and social benefits of each. Given other
countries' interest in pursuing exploration, timing is of the essence.
---------------------------------------------------------
Title: Study of Quiet Sun Through the Solar Atmosphere: From the
Chromosphere Up to Coronal Layers
Authors: Abbo, L.; Gabriel, A.; Harra, L.
2009ASPC..415..389A Altcode:
We analyze intensity maps over a range of temperatures covering the
chromosphere to the solar corona, near a polar coronal hole. Using
observations from EIS spectrometer on Hinode, we examine the width of
the network boundary as a function of temperature. Very preliminary
results show that there is a gradual increasing of the network boundary
width through the transition region up to coronal layers. Existing
observations are being studied and newer observation plans are currently
under way.
---------------------------------------------------------
Title: Signatures of interchange reconnection: STEREO, ACE and Hinode
observations combined
Authors: Baker, D.; Rouillard, A. P.; van Driel-Gesztelyi, L.;
Démoulin, P.; Harra, L. K.; Lavraud, B.; Davies, J. A.; Opitz, A.;
Luhmann, J. G.; Sauvaud, J. -A.; Galvin, A. B.
2009AnGeo..27.3883B Altcode: 2009arXiv0909.5624B
Combining STEREO, ACE and Hinode observations has presented an
opportunity to follow a filament eruption and coronal mass ejection
(CME) on 17 October 2007 from an active region (AR) inside a coronal
hole (CH) into the heliosphere. This particular combination of
"open" and closed magnetic topologies provides an ideal scenario for
interchange reconnection to take place. With Hinode and STEREO data
we were able to identify the emergence time and type of structure
seen in the in-situ data four days later. On the 21st, ACE observed
in-situ the passage of an ICME with "open" magnetic topology. The
magnetic field configuration of the source, a mature AR located
inside an equatorial CH, has important implications for the solar and
interplanetary signatures of the eruption. We interpret the formation of
an "anemone" structure of the erupting AR and the passage in-situ of the
ICME being disconnected at one leg, as manifested by uni-directional
suprathermal electron flux in the ICME, to be a direct result of
interchange reconnection between closed loops of the CME originating
from the AR and "open" field lines of the surrounding CH.
---------------------------------------------------------
Title: On-disk signatures of eruptive activity from the Hinode mission
Authors: Harra, Louise K.
2009AdSpR..44..446H Altcode:
On-disk signatures of eruptive activity have been investigated for
many years. These include filament eruptions, flares, coronal waves
and dimmings. The Hinode mission is providing a new perspective on
eruptive activity on the Sun and its linkage to the Earth. Despite being
in a period of solar minimum since the launch of Hinode in September
2006, observations have been made of flares and coronal mass ejections
(CMEs). A description of flare and CME triggers are presented, followed
by a description of the impact of the eruption on the surrounding
corona. A review of the more recent results achieved predominantly
from the Hinode space mission are given. Some discussion of the future
potential is described as a new solar cycle is beginning a slow start.
---------------------------------------------------------
Title: Evidence from the Extreme-Ultraviolet Imaging Spectrometer
for Axial Filament Rotation before a Large Flare
Authors: Williams, David R.; Harra, Louise K.; Brooks, David H.;
Imada, Shinsuke; Hansteen, Viggo H.
2009PASJ...61..493W Altcode:
In this article, we present observations made with the
Extreme-ultraviolet Imaging Spectrometer on-board the Hinode solar
satellite, of an active region filament in the HeII emission line at
256.32Å. The host active region AR 10930 produces an X-class flare
during these observations. We measure Doppler shifts with apparent
velocities of up to 20km s<SUP>-1</SUP>, which are antisymmetric about
the filament length and occur several minutes before the flare's
impulsive phase. This is indicative of a rotation of the filament,
which is in turn consistent with expansion of a twisted flux rope due
to the MHD helical kink instability. This is the first time that such
an observation has been possible in this transition-region line, and we
note that the signature observed occurs before the first indications of
pre-flare activity in the GOES solar soft X-ray flux, suggesting that
the filament begins to destabilise in tandem with a reorganization of
the local magnetic field. We suggest that this expansion is triggered
by the decrease of magnetic tension around, and/or total pressure above,
the filament.
---------------------------------------------------------
Title: Hinode “a new solar observatory in space”
Authors: Tsuneta, S.; Harra, L. K.; Masuda, S.
2009cwse.conf...63T Altcode:
Since its launch in September 2006, the Japan-US-UK solar physics
satellite, Hinode, has continued its observation of the sun, sending
back solar images of unprecedented clarity every day. Hinode is equipped
with three telescopes, a visible light telescope, an X-ray telescope,
and an extreme ultraviolet imaging spectrometer. The Hinode optical
telescope has a large primary mirror measuring 50 centimeters in
diameter and is the world's largest space telescope for observing the
sun and its vector magnetic fields. The impact of Hinode as an optical
telescope on solar physics is comparable to that of the Hubble Space
Telescope on optical astronomy. While the optical telescope observes
the sun's surface, the Hinode X-ray telescope captures images of the
corona and the high-temperature flares that range between several
million and several tens of millions of degrees. The telescope has
captured coronal structures that are clearer than ever. The Hinode
EUV imaging spectrometer possesses approximately ten times the
sensitivity and four times the resolution of a similar instrument on
the SOHO satellite. The source of energy for the sun is in the nuclear
fusion reaction that takes place at its core. Here temperature drops
closer to the surface, where the temperature measures about 6,000
degrees. Mysteriously, the temperature starts rising again above the
surface, and the temperature of the corona is exceptionally high,
several millions of degrees. It is as if water were boiling fiercely
in a kettle placed on a stove with no fire, inconceivable as it may
sound. The phenomenon is referred to as the coronal heating problem, and
it is one of the major astronomical mysteries. The Hinode observatory
was designed to solve this mystery. It is expected that Hinode would
also provide clues to unraveling why strong magnetic fields are formed
and how solar flares are triggered. An overview on the initial results
from Hinode is presented. Dynamic video pictures captured by Hinode
can be viewed on the website of the National Astronomical Observatory
of Japan (NAOJ) at http://hinode.nao.ac.jp/index_e.shtml
---------------------------------------------------------
Title: POLAR investigation of the Sun—POLARIS
Authors: Appourchaux, T.; Liewer, P.; Watt, M.; Alexander, D.;
Andretta, V.; Auchère, F.; D'Arrigo, P.; Ayon, J.; Corbard, T.;
Fineschi, S.; Finsterle, W.; Floyd, L.; Garbe, G.; Gizon, L.; Hassler,
D.; Harra, L.; Kosovichev, A.; Leibacher, J.; Leipold, M.; Murphy,
N.; Maksimovic, M.; Martinez-Pillet, V.; Matthews, B. S. A.; Mewaldt,
R.; Moses, D.; Newmark, J.; Régnier, S.; Schmutz, W.; Socker, D.;
Spadaro, D.; Stuttard, M.; Trosseille, C.; Ulrich, R.; Velli, M.;
Vourlidas, A.; Wimmer-Schweingruber, C. R.; Zurbuchen, T.
2009ExA....23.1079A Altcode: 2008ExA...tmp...40A; 2008arXiv0805.4389A
The POLAR Investigation of the Sun (POLARIS) mission uses a combination
of a gravity assist and solar sail propulsion to place a spacecraft
in a 0.48 AU circular orbit around the Sun with an inclination of 75°
with respect to solar equator. This challenging orbit is made possible
by the challenging development of solar sail propulsion. This first
extended view of the high-latitude regions of the Sun will enable
crucial observations not possible from the ecliptic viewpoint or from
Solar Orbiter. While Solar Orbiter would give the first glimpse of
the high latitude magnetic field and flows to probe the solar dynamo,
it does not have sufficient viewing of the polar regions to achieve
POLARIS’s primary objective: determining the relation between the
magnetism and dynamics of the Sun’s polar regions and the solar cycle.
---------------------------------------------------------
Title: Coronal Nonthermal Velocity Following Helicity Injection
Before an X-Class Flare
Authors: Harra, L. K.; Williams, D. R.; Wallace, A. J.; Magara, T.;
Hara, H.; Tsuneta, S.; Sterling, A. C.; Doschek, G. A.
2009ApJ...691L..99H Altcode:
We explore the "pre-flare" behavior of the corona in a three-day
period building up to an X-class flare on 2006 December 13 by analyzing
EUV spectral profiles from the Hinode EUV Imaging Spectrometer (EIS)
instrument. We found an increase in the coronal spectral line widths,
beginning after the time of saturation of the injected helicity as
measured by Magara & Tsuneta. In addition, this increase in line
widths (indicating nonthermal motions) starts before any eruptive
activity occurs. The Hinode EIS has the sensitivity to measure changes
in the buildup to a flare many hours before the flare begins.
---------------------------------------------------------
Title: Flux Rope Eruption From the Sun to the Earth: What do Reversals
in the Azimuthal Magnetic Field Gradient Tell us About the Evolution
of the Magnetic Structure?
Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso,
S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L.
2008AGUFMSH23B1638S Altcode:
Using ACE in situ data we identify and describe an interplanetary
magnetic cloud (MC) observed near Earth on 13 April 2006. We also use
multi-instrument and multi-wavelength observations from SOHO, TRACE and
ground-based solar observatories to determine the solar source of this
magnetic cloud. A launch window for the MC between 9 and 11 April 2006
was estimated from the propagation time of the ejecta observed near
Earth. A number of large active regions were present on the Sun during
this period, which were initially considered to be the most likely
candidate source regions of the MC. However, it was determined that
the solar source of the MC was a small, spotless active region observed
in the Northern Hemisphere. Following an eruption from this region on
11 April 2006, the ACE spacecraft detected, 59 h later, the passage of
the MC, preceded by the arrival of a weak, forward fast shock. The link
between the eruption in this active region and the interplanetary MC is
supported by several pieces of evidence, including the location of the
solar source near to the disk centre and to the east of the central
meridian (in agreement with the spacecraft trajectory through the
western leg of the magnetic cloud), the propagation time of the ejecta,
the agreement between the amount of flux in the magnetic cloud and in
the active region, and the agreement between the signs of helicity of
the magnetic cloud and the active region (which differs from the sign
of helicity of each of the other active regions on the Sun at this
time). In addition, the active region is located on the boundary of
a coronal hole, and a high speed solar wind stream originating from
this region is observed near Earth shortly after the passage of the
magnetic cloud. This event highlights the complexities associated
with locating the solar source of an ICME observed near Earth, and
serves to emphasise that it is the combination of a number of physical
characteristics and signatures that is important for successfully
tying together the Earth-end and the Sun-end of an event. Further
investigation of this MC has revealed some sub-structure towards its
centre, observed as a small scale reversal of the azimuthal magnetic
field of the MC, similar to that reported by Dasso et al., 2007. We
explore several possible explanations for this signature, including
the occurrence of multiple flux ropes and/or warping of the magnetic
cloud. We also consider whether magnetic reconnection plays a role in
creating the geometry that would explain these observations.
---------------------------------------------------------
Title: The Recovery of CME-Related Dimmings and the ICME's Enduring
Magnetic Connection to the Sun
Authors: Attrill, G. D. R.; van Driel-Gesztelyi, L.; Démoulin, P.;
Zhukov, A. N.; Steed, K.; Harra, L. K.; Mandrini, C. H.; Linker, J.
2008SoPh..252..349A Altcode: 2008SoPh..tmp..158A
It is generally accepted that transient coronal holes (TCHs, dimmings)
correspond to the magnetic footpoints of CMEs that remain rooted in
the Sun as the CME expands out into the interplanetary space. However,
the observation that the average intensity of the 12 May 1997 dimmings
recover to their pre-eruption intensity in SOHO/EIT data within 48
hours, whilst suprathermal unidirectional electron heat fluxes are
observed at 1 AU in the related ICME more than 70 hours after the
eruption, leads us to question why and how the dimmings disappear
whilst the magnetic connectivity is maintained. We also examine two
other CME-related dimming events: 13 May 2005 and 6 July 2006. We study
the morphology of the dimmings and how they recover. We find that, far
from exhibiting a uniform intensity, dimmings observed in SOHO/EIT data
have a deep central core and a more shallow extended dimming area. The
dimmings recover not only by shrinking of their outer boundaries but
also by internal brightenings. We quantitatively demonstrate that the
model developed by Fisk and Schwadron (Astrophys. J.560, 425, 2001)
of interchange reconnections between "open" magnetic field and small
coronal loops is a strong candidate for the mechanism facilitating the
recovery of the dimmings. This process disperses the concentration of
"open" magnetic field (forming the dimming) out into the surrounding
quiet Sun, thus recovering the intensity of the dimmings whilst still
maintaining the magnetic connectivity to the Sun.
---------------------------------------------------------
Title: Why are CMEs large-scale coronal events: nature or nurture?
Authors: van Driel-Gesztelyi, L.; Attrill, G. D. R.; Démoulin, P.;
Mandrini, C. H.; Harra, L. K.
2008AnGeo..26.3077V Altcode:
The apparent contradiction between small-scale source regions of,
and large-scale coronal response to, coronal mass ejections (CMEs)
has been a long-standing puzzle. For some, CMEs are considered to
be inherently large-scale events eruptions in which a number of flux
systems participate in an unspecified manner, while others consider
magnetic reconnection in special global topologies to be responsible
for the large-scale response of the lower corona to CME events. Some
of these ideas may indeed be correct in specific cases. However,
what is the key element which makes CMEs large-scale? Observations
show that the extent of the coronal disturbance matches the angular
width of the CME an important clue, which does not feature strongly
in any of the above suggestions. We review observational evidence
for the large-scale nature of CME source regions and find them
lacking. Then we compare different ideas regarding how CMEs evolve
to become large-scale. The large-scale magnetic topology plays an
important role in this process. There is amounting evidence, however,
that the key process is magnetic reconnection between the CME and other
magnetic structures. We outline a CME evolution model, which is able
to account for all the key observational signatures of large-scale
CMEs and presents a clear picture how large portions of the Sun become
constituents of the CME. In this model reconnection is driven by the
expansion of the CME core resulting from an over-pressure relative to
the pressure in the CME's surroundings. This implies that the extent of
the lower coronal signatures match the final angular width of the CME.
---------------------------------------------------------
Title: Locating the solar source of 13 April 2006 magnetic cloud
Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso,
S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L.
2008AnGeo..26.3159S Altcode:
Using Advanced Composition Explorer (ACE) in situ data we identify and
describe an interplanetary magnetic cloud (MC) observed near Earth
on 13 April 2006. We also use multi-instrument and multi-wavelength
observations from the Solar and Heliospheric Observatory (SOHO), the
Transition Region and Coronal Explorer (TRACE) and ground-based solar
observatories to determine the solar source of this magnetic cloud. A
launch window for the MC between 9 and 11 April 2006 was estimated from
the propagation time of the ejecta observed near Earth. A number of
large active regions (ARs) were present on the Sun during this period,
which were initially considered to be the most likely candidate source
regions of the MC. However, it was determined that the solar source
of the MC was a small, spotless active region observed in the Northern
Hemisphere. Following an eruption from this region on 11 April 2006, the
ACE spacecraft detected, 59 h later, the passage of the MC, preceded by
the arrival of a weak, forward fast shock. The link between the eruption
in this active region and the interplanetary MC is supported by several
pieces of evidence, including the location of the solar source near to
the disk centre and to the east of the central meridian (in agreement
with the spacecraft trajectory through the western leg of the magnetic
cloud), the propagation time of the ejecta, the agreement between
the amount of flux in the magnetic cloud and in the active region,
and the agreement between the signs of helicity of the magnetic cloud
and the active region (which differs from the sign of helicity of each
of the other active regions on the Sun at this time). In addition,
the active region is located on the boundary of a coronal hole, and a
high speed solar wind stream originating from this region is observed
near Earth shortly after the passage of the magnetic cloud.
---------------------------------------------------------
Title: Multi-scale reconnections in a complex CME
Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Démoulin, P.; Culhane,
J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. -L.;
Kurokawa, H.
2008AdSpR..42..858V Altcode:
A series of three flares of GOES class M, M and C, and a CME were
observed on 20 January 2004 occurring in close succession in NOAA
10540. Types II, III, and N radio bursts were associated. We use
the combined observations from TRACE, EIT, Hα images from Kwasan
Observatory, MDI magnetograms, GOES, and radio observations from
Culgoora and Wind/ WAVES to understand the complex development of this
event. We reach three main conclusions. First, we link the first two
impulsive flares to tether-cutting reconnections and the launch of
the CME. This complex observation shows that impulsive quadrupolar
flares can be eruptive. Second, we relate the last of the flares, an
LDE, to the relaxation phase following forced reconnections between
the erupting flux rope and neighbouring magnetic field lines, when
reconnection reverses and restores some of the pre-eruption magnetic
connectivities. Finally, we show that reconnection with the magnetic
structure of a previous CME launched about 8 h earlier injects electrons
into open field lines having a local dip and apex (located at about six
solar radii height). This is observed as an N-burst at decametre radio
wavelengths. The dipped shape of these field lines is due to large-scale
magnetic reconnection between expanding magnetic loops and open field
lines of a neighbouring streamer. This particular situation explains
why this is the first N-burst ever observed at long radio wavelengths.
---------------------------------------------------------
Title: Study of the Physical Properties of Coronal “Waves” and
Associated Dimmings
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
Williams, D.; Alexeev, I. V.
2008ASPC..397..126A Altcode:
We present results from our study run by Hinode, designed to obtain
information on the physical properties of the diffuse bright fronts
known as “EIT coronal waves” and their associated dimmings. We
analyse data obtained during a frustrated eruption event on 5th May
2007. The event produces a bright front as well as deep and shallow
dimmings. We show that the dimmings of this frustrated eruption
show similar physical properties to those observed in textbook “EIT
coronal wave” events. The Hinode/EIS data show that both the deep
and shallow dimmings associated with this frustrated eruption show
blue-shifted velocities. It is therefore consistent that, like the
deep core dimmings, the widespread shallow dimmings observed with many
textbook coronal “wave” events may also be due to plasma outflows.
---------------------------------------------------------
Title: First Results From Hinode
Authors: Matthews, S. A.; Davis, J. M.; Harra, L. K.
2008ASPC..397.....M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Long Duration Flare Observed with Hinode EIS
Authors: Culhane, J. L.; Hara, H.; Watanabe, T.; Matsuzaki, K.; Harra,
L. K.; Cargill, P.; Mariska, J. T.; Doschek, G. A.
2008ASPC..397..121C Altcode:
The first Long Duration Event (LDE) observed with Hinode EIS using
a high spectral resolution raster scan is described. The hot plasma
features include a cusp-shaped arcade associated with a thermal RHESSI
source, cooling post-flare loops, complex plasma flows and an EIT
observation that shows expanding loops and inflows characteristic of
the standard magnetic reconnection model for solar flares. A Coronal
Mass Ejection (CME) is also seen by LASCO. The cusp is well observed
in the Ca XVII line and we find enhanced line broadening above this
region. Doppler velocity observations for the post-flare loops show both
up-flows and down-flows that are interpreted as due to siphon flows.
---------------------------------------------------------
Title: Solar Flares and Coronal Mass Ejections: a New View with Hinode
Authors: Harra, L. K.
2008ASPC..397...91H Altcode:
Less than a year since Hinode was launched many flares and coronal
mass ejections have already been observed, in particular four
X-classification flares and fifteen M-classification flares. In this
paper I will review the first results on flares and coronal mass
ejections from the three instruments on Hinode. I will cover aspects
relating to the all important phase building up to a flare, the flare
itself and finally the global response of flares.
---------------------------------------------------------
Title: Hinode EIS and XRT Observations of Hot Jets in Coronal Holes -
Does the Plasma Escape?
Authors: Baker, D.; van Driel-Gesztelyi, L.; Kamio, S.; Culhane,
J. L.; Harra, L. K.; Sun, J.; Young, P. R.; Matthews, S. A.
2008ASPC..397...23B Altcode:
X-ray jets have been detected in the extreme ultraviolet (EUV) and
soft X-ray observations of Hinode's EIS and XRT instruments. Both
instruments were used to observe the jets in polar and on-disk coronal
holes (CHs). Here, we present a multi-wavelength study of an X-ray
jet and its associated bright point found in an equatorial CH on 19
June 2007. Light curves (LCs) in 22 different emission lines were
compared to that of Hinode/XRT. As we found in a previous study of
two polar X-ray jets, this jet shows a post-jet increase in its EUV
LCs. The post-jet enhancement appears cooler than the jet. We suggest
this feature arises because the hot plasma of the jet, having failed to
reach escape speeds, cools and falls back along the near vertical paths
expected to be created by reconnection with open field lines of CHs. In
addition to the increase in post-jet EUV intensity, we found tentative
evidence of impact heating possibly caused by the fall-back of plasma.
---------------------------------------------------------
Title: Doppler Shifts in the Boundary of the Dimming Region
Authors: Imada, S.; Hara, H.; Watanabe, T.; Asai, A.; Kamio, S.;
Matsuzaki, K.; Harra, L. K.; Mariska, J. T.
2008ASPC..397..102I Altcode:
We present Hinode/EIS raster scan observations of the GOES X3.2
flare that occurred on 2006 December 13. There was a small transient
coronal hole which was located 200 arcsec east of the flare arcade. The
transient coronal hole was strongly affected by the X-class flare, and
the strong upflows were observed in Fe XV line 284.2 Å (log{T/{K}}
= 6.3) at the boundary of dimming region. In this paper, we discuss
how to obtain the velocity map by correcting the instrumental effects.
---------------------------------------------------------
Title: Non-Gaussian Line Profiles in a Large Solar Flare Observed
on 2006 December 13
Authors: Imada, S.; Hara, H.; Watanabe, T.; Asai, A.; Minoshima, T.;
Harra, L. K.; Mariska, J. T.
2008ApJ...679L.155I Altcode:
We have studied the characteristics of the non-Gaussian line profile
of the Fe XIV 274.20 Å line in and around a flare arcade. We found
that broad non-Gaussian line profiles associated with redshifts
are observed in the flare arcade. There were two typical types
of broad line profiles. One was a distorted line profile caused by
multiple flows, and the other was a symmetric line profile without any
additional component. We successfully distinguished those two types
using higher order statistical moments or M—the additional component
contribution—defined in this Letter. The distorted/symmetric broad
line profiles were preferentially observed in new/old flare loops,
respectively.
---------------------------------------------------------
Title: Coronal Plasma Motions near Footpoints of Active Region Loops
Revealed from Spectroscopic Observations with Hinode EIS
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.; Mariska, John T.; Doschek, George A.
2008ApJ...678L..67H Altcode:
The solar active region 10938 has been observed from the disk center
to the west limb with the Hinode EUV Imaging Spectrometer. In the
disk-center observation, subsonic upflow motions of tens of km
s<SUP>-1</SUP> and enhanced nonthermal velocities have been found
near the footpoints of the active region loops assuming a single
Gaussian approximation for the emission-line profiles. When the same
part of the active region is observed near the limb, both upflows
and enhanced nonthermal velocities essentially decrease. There
is a strong correlation between Doppler velocity and nonthermal
velocity. Significant deviations from a single Gaussian profile are
found in the blue wing of the line profiles for the upflows. These
suggest that there are unresolved high-speed upflows. We discuss the
implications for coronal heating mechanisms.
---------------------------------------------------------
Title: Outflows at the Edges of Active Regions: Contribution to
Solar Wind Formation?
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
2008ApJ...676L.147H Altcode:
The formation of the slow solar wind has been debated for many years. In
this Letter we show evidence of persistent outflow at the edges of
an active region as measured by the EUV Imaging Spectrometer on board
Hinode. The Doppler velocity ranged between 20 and 50 km s<SUP>-1</SUP>
and was consistent with a steady flow seen in the X-Ray Telescope. The
latter showed steady, pulsing outflowing material and some transverse
motions of the loops. We analyze the magnetic field around the active
region and produce a coronal magnetic field model. We determine from
the latter that the outflow speeds adjusted for line-of-sight effects
can reach over 100 km s<SUP>-1</SUP>. We can interpret this outflow as
expansion of loops that lie over the active region, which may either
reconnect with neighboring large-scale loops or are likely to open to
the interplanetary space. This material constitutes at least part of
the slow solar wind.
---------------------------------------------------------
Title: 2006 December 17 Long Duration Flare Observed with the Hinode
EUV Imaging Spectrometer
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Matsuzaki, Keiichi; Harra,
Louise K.; Culhane, J. Leonard; Cargill, Peter; Mariska, John T.;
Doschek, George A.
2008PASJ...60..275H Altcode:
A GOES C-class long-duration flare that occurred near the west limb on
2006 December 17 was observed with the Hinode EUV Imaging Spectrometer
(EIS) in raster-scan observations. Cusp-shaped arcades are prominent in
the spectroheliogram of the CaXVII emission line at 192.86Å. Spatial
relationships between hot flare loops with a cusp apex and cool post
flare loops with various temperatures are clearly shown in the EIS
observations. We find an enhanced line broadening above the bright
loop-top region in the CaXVII observation. The Doppler observations of
cooling post flare loops with coronal temperatures show both downflows
and upflows along the loops, and these are interpreted as a part of
siphon flows. Enhanced nonthermal line broadenings are identified at
the top of the post flare loops.
---------------------------------------------------------
Title: Erratum: "Outflows at the Edges of Active Regions: Contribution
to Solar Wind Formation?" (ApJ, 676, L147 [2008])
Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada,
S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D.
2008ApJ...677L.159H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On-disc signatures of eruptive activity: Broad perspective
Authors: Harra, Louise K.
2008cosp...37.1180H Altcode: 2008cosp.meet.1180H
The Hinode and STEREO missions are providing a new perspective on
eruptive activity on the Sun and its linkage to the Earth. This
talk will review all aspects eruptive activity from the very small
scale (jets in coronal holes) to the large scale (EIT ‘coronal'
waves). These different scales of on-disc signatures provide
contribution to the fast and slow solar winds and of course the more
dramatic coronal mass ejections.
---------------------------------------------------------
Title: Spectroscopic observations of coronal waves and coronal
mass ejections
Authors: Harra, L. K.
2008AdSpR..41..138H Altcode:
It is common to use imaging instruments such as EUV and X-ray imagers
and coronagraphs to study large-scale phenomena such as coronal mass
ejections and coronal waves. Although high resolution spectroscopy
is generally limited to a small field of view, its importance in
understanding global phenomena should not be under-estimated. I will
review current spectroscopic observations of large-scale dynamic
phenomena such as global coronal waves and coronal mass ejections. The
aim is to determine plasma parameters such as flows, temperatures and
densities to obtain a physical understanding of these phenomena.
---------------------------------------------------------
Title: a New View of the Sun from the Hinode Space Mission
Authors: Harra, Louise K.
2008IJMPD..17..693H Altcode:
The Japanese/US/UK space mission, Hinode, was launched successfully
in September 2006. Now, more than a year after the commissioning of
the spacecraft and instruments, Hinode is unveiling a new view of the
Sun. Hinode's goal is to help us to understand solar activity, and to
link activity on (and below) the surface to the outer corona. This
review will describe how the initial results are overturning our
understanding of the Sun and will look to the future to anticipate
what further discoveries might be made. In particular I will describe
the areas of basic magnetohydrodynamic (MHD) processes such as magnetic
reconnection and Alfvén waves, the formation of both the fast and slow
solar winds and the triggering of flares and coronal mass ejections.
---------------------------------------------------------
Title: Breaking or maintaining magnetic connection of CMEs to the
Sun - solar vs. interplanetary signatures tested
Authors: van Driel-Gesztelyi, Lidia; Attrill, Gemma; Demoulin, Pascal;
Mandrini, Cristina H.; Harra, Louise K.
2008cosp...37.3287V Altcode: 2008cosp.meet.3287V
Though their relationship is complex, the presence of suprathermal
unior bi-directional electron streams in ICMEs are treated as
signatures of magnetic field lines with one or both ends being
connected to the Sun, respectively, while their absence is
interpreted as disconnection. However, do we have any reliable
signature in the solar corona distinguishing between maintained
connection and disconnection? We test two solar signatures against
interplanetary suprathermal electron signatures in order to establish
their relevance. We test the hypothesis that the recovery of Transient
Coronal Holes (TCHs, dimming regions corresponding to the footpoints of
CMEs) is a signature of magnetic disconnection from the Sun. Through
three case studies we quantitatively demonstrate that magnetic
reconnections between field lines of the expanded CME magnetic field
and small coronal loops can act to disperse the concentration of
CME footpoints (forming the dimming region) out into the surrounding
quiet Sun, thus recovering the intensity of the dimming region whilst
still maintaining the magnetic connectivity to the Sun. This analysis
provides evidence that the recovery of coronal dimming regions can,
in fact, be simply reconciled with maintained magnetic connectivity
to the Sun. However, disconnection can occur when open field lines are
involved in reconnection with CMEs. We show through two well-observed
case studies that magnetic reconnection between the expanding CME and
a nearby coronal hole (CH) is indeed able to disconnect one leg of
the expanding CME magnetic structure, as indicated by uni-directional
electron streams in their respective ICMEs. Therefore we suggest that
brightenings (signatures of reconnection) appearing along a coronal
hole boundary in the wake of a CME can be treated as a signature of
(at least partial) disconnection of one of the CME legs from the Sun.
---------------------------------------------------------
Title: Coronal Plasma Motions near Footpoints of Active Region Loops
Revealed from Spectroscopic Observations with {it Hinode} EIS
Authors: Hara, Hirohisa; Watanabe, Tetsuya; Harra, Louise K.; Culhane,
J. Leonard; Young, Peter R.; Doschek, G. A.; Mariska, John
2008cosp...37.1175H Altcode: 2008cosp.meet.1175H
We have observed the solar active region 10938 from the disk center
to the west limb with the Hinode EUV Imaging Spectrometer. In the
disk center observation subsonic upflow motions of tens of km s-1 and
enhanced nonthermal velocities have been found near the footpoints of
the active-region loops assuming a single Gaussian approximation for
the emission-line profiles. When the same part of the active region
is observed near the limb, both upflows and enhanced nonthermal
velocities essentially decrease, clearly showing that the enhanced
nonthermal velocities in the disk center observation are mainly due to
line-of-sight motions, which are likely parallel to magnetic field lines
of the coronal loops. There is a strong correlation between Doppler
velocity and nonthermal velocity in the upflow regions. The enhancement
in the blue wing of the line profiles is found for the upflows as a
significant deviation from a single Gaussian profile. These suggest
that there are unresolved high-speed upflows near the footpoints of
active region loops. We discuss the implications for coronal heating
mechanisms.
---------------------------------------------------------
Title: Structures in flaring loops seen in FeXXIII 263.76A line
Authors: Watanabe, T.; Doschek, G. A.; Harra, L. K.; Hara, H.
2007AGUFMSH52C..03W Altcode:
EIS observed the highest temperature lines of FeXXIII263.76A,
FeXXIV192.10A, 255.10A in the EIS observing wavelengths during a C4.2
flare occurred on 16-Jan-07, as well as an FeXVII line at 254.83A. The
raster scan of the flaring area took place during 2:36 - 2:41 UT nearly
at the maximum phase of the flare. Comparing a monochromatic FeXXIII
raster image with the other high spatial resolution images taken by the
instruments on board the Hinode and those by Nobeyama Radio Heliograph,
electron precipitation cites are indentified. Foot points with fast
chromospheric evaporation are compact at the size of a few arcseconds,
and the turbulence still remain around the top of flaring loops. Down
flows are also seen in the lower temperature lines just outside the
flaring loops.
---------------------------------------------------------
Title: Continuous Plasma Outflows from the Edge of a Solar Active
Region as a Possible Source of Solar Wind
Authors: Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku,
Jun'ichi; Bando, Takamasa; DeLuca, Edward E.; Lundquist, Loraine L.;
Tsuneta, Saku; Harra, Louise K.; Katsukawa, Yukio; Kubo, Masahito;
Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay
A.; Golub, Leon; Korreck, Kelly E.; Su, Yingna; Shibasaki, Kiyoto;
Shimizu, Toshifumi; Nakatani, Ichiro
2007Sci...318.1585S Altcode:
The Sun continuously expels a huge amount of ionized material into
interplanetary space as the solar wind. Despite its influence on the
heliospheric environment, the origin of the solar wind has yet to
be well identified. In this paper, we report Hinode X-ray Telescope
observations of a solar active region. At the edge of the active region,
located adjacent to a coronal hole, a pattern of continuous outflow of
soft-x-ray emitting plasmas was identified emanating along apparently
open magnetic field lines and into the upper corona. Estimates of
temperature and density for the outflowing plasmas suggest a mass
loss rate that amounts to ~1/4 of the total mass loss rate of the
solar wind. These outflows may be indicative of one of the solar wind
sources at the Sun.
---------------------------------------------------------
Title: The Structure and Dynamics of the Quiet Corona from
Observations with the Extreme ultraviolet Imaging Spectrometer
Authors: Dere, K. P.; Doschek, G. A.; Mariska, J. T.; Harra, L. K.;
Matsuzaki, K.; Hansteen, V.; Thomas, R. J.
2007AGUFMSH53A1046D Altcode:
The goal of the Extreme-ultraviolet Imaging Spectrometer (EIS) on the
Hinode satellite is to measure such physical parameters as the velocity
and density of the solar corona in order to provide an observational
basis to understand how coronal plasmas are heated and accelerated. On
2007 January 20, EIS performed a raster of a 128 x 512 arc-sec. area
of a quiet region near Sun center. The observing program recorded
spectra of He II λ256, formed at 9 × 104 K, and lines of Fe VIII-XV,
formed at temperatures spanning the range from 5 × 105 through 2 × 106
K. Maps of intensities, velocities and electron densities derived from
these observations are presented and discussed. Intensity maps in He II
λ256 show the chromospheric network. Line intensities of Fe X-XIV show
small-scale bright points and more extended structures. The intensity
map of Fe VIII shows a transition between the two temperatures. The
coronal lines reveal regions of high outflow velocities on the
order of 100 km s-1 in a compact region and 12 km s-1 in an extended
region. The presence of these high velocities in the quiet corona
is an entirely new and unexpected result. Electron densities derived
from density sensitive line ratios of Fe XII and XIII are typically
about 3 - 20×108 cm-3. The highest densities are found in bright,
compact areas. For the first time, explosive events in the quiet sun
have been observed in the extreme-ultraviolet in He II λ256 profiles
and have properties similar to those previously reported.
---------------------------------------------------------
Title: The Structure and Dynamics of the Quiet Corona from
Observations with the Extreme Ultraviolet Imaging Spectrometer
on Hinode
Authors: Dere, Kenneth P.; Doschek, George A.; Mariska, John T.;
Hansteen, Viggo H.; Harra, Louise K.; Matsuzaki, Keiichi; Thomas,
Roger J.
2007PASJ...59S.721D Altcode:
The goal of the Hinode mission is to provide an observational basis for
understanding the heating and acceleration of coronal plasmas. On 2007
January 20, the Extreme ultraviolet Imaging Spectrometer performed
a raster of a quiet region near Sun center. Maps of intensities,
velocities, and electron densities derived from these observations are
presented and discussed. Intensity maps in HeII λ 256, formed at 9
× 10<SUP>4</SUP> K, show the chromospheric network. Line intensities
of FeX-XIV, formed at temperatures from 1-2 × 10<SUP>6</SUP> K, show
small-scale bright points and more extended structures. The intensity
map of FeVIII shows a transition between the two temperatures. The
coronal lines reveal regions of high outflow velocities on the order
of 100kms<SUP>-1</SUP> in a compact region and 12kms<SUP>-1</SUP> in
an extended region. The presence of such high velocities in the quiet
corona is an entirely new and unexpected result. Electron densities
derived from density sensitive line ratios of FeXII and XIII are
typically 3-20 × 10<SUP>8</SUP>cm<SUP>-3</SUP>. The highest densities
are found in bright, compact areas. For the first time, explosive
events in the quiet sun have been observed in the extreme-ultraviolet
in HeII λ 256 profiles.
---------------------------------------------------------
Title: Hinode EUV Study of Jets in the Sun's South Polar Corona
Authors: Culhane, Len; Harra, Louise K.; Baker, Deborah; van
Driel-Gesztelyi, Lidia; Sun, Jian; Doschek, George A.; Brooks, David
H.; Lundquist, Loraine L.; Kamio, Suguru; Young, Peter R.; Hansteen,
Viggo H.
2007PASJ...59S.751C Altcode:
A number of coronal bright points and associated plasma jet features
were seen in an observation of the South polar coronal hole during
2007 January. The 40" wide slot was used at the focus of the Hinode
EUV Imaging Spectrometer to provide spectral images for two of these
events. Light curves are plotted for a number of emission lines that
include He II 256Å (0.079MK) and cover the temperature interval from
0.4MK to 5.0MK. Jet speed measurements indicate values less than the
escape velocity. The light curves show a post-jet enhancement in a
number of the cooler coronal lines indicating that after a few minutes
cooling, the plasma fell back to its original acceleration site. This
behavior has not been previously observed by e.g., the Yohkoh Soft
X-ray Telescope due to the comparatively high temperature cut-off
in its response. The observations are consistent with the existing
models that involve magnetic reconnection between emerging flux and the
ambient open field lines in the polar coronal hole. However we do not
have sufficient coverage of lines from lower temperature ion species
to register the Hα-emitting surge material that is associated with
some of these models.
---------------------------------------------------------
Title: Temperature and Density Structures of Solar Corona, A Test
of Iron Line Diagnostic Capability of EIS Instrument on Board Hinode
Authors: Watanabe, Tetsuya; Hara, Hirohisa; Culhane, Len; Harra,
Louise K.; Doschek, George A.; Mariska, John T.; Young, Peter R.
2007PASJ...59S.669W Altcode:
Increased diagnostic capability of the EUV Imaging Spectrometer
(EIS) aboard Hinode (former Solar-B) has been demonstrated with
a set of iron emission lines emerging in the two EIS observing
wavelength bands (170-210Å and 250-290Å) and their line-intensity
ratios. “Abundance-uncertainty” free relative emission measure
distributions as a function of temperature were deduced using only iron
emission lines of various ionization stages. First-light spectra of a
small active region show iron lines ranging from FeVIII (185.2Å and
186.6Å) through FeXVII (204.7Å, 254.9Å, and 269.4Å). Spectra of a
C-class flare confirms the presence of one of these higher temperature
lines (FeXVII at 254.9Å) more clearly, as well showing FeXXIV (192.0Å
and 255.1Å) and FeXXIII (263.8Å), which are normally only seen at
flare temperatures.
---------------------------------------------------------
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
2007PASJ...59S.699H Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
---------------------------------------------------------
Title: EUV Emission Lines and Diagnostics Observed with Hinode/EIS
Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Dere,
Ken P.; Landi, Enrico; Landini, Massimo; Doschek, George A.; Brown,
Charles M.; Culhane, Len; Harra, Louise K.; Watanabe, Tetsuya; Hara,
Hirohisa
2007PASJ...59S.857Y Altcode: 2007arXiv0706.1857Y
Quiet Sun and active region spectra from the Hinode/EIS instrument are
presented, and the strongest lines from different temperature regions
discussed. A list of emission lines recommended to be included in EIS
observation studies is presented based on analysis of blending and
diagnostic potential using the CHIANTI atomic database. In addition
we identify the most useful density diagnostics from the ions covered
by EIS.
---------------------------------------------------------
Title: Discovery of a Temperature-Dependent Upflow in the Plage
Region During a Gradual Phase of the X-Class Flare
Authors: Imada, Shinsuke; Hara, Hirohisa; Watanabe, Tetsuya; Kamio,
Suguru; Asai, Ayumi; Matsuzaki, Keiichi; Harra, Louise K.; Mariska,
John T.
2007PASJ...59S.793I Altcode:
We present Hinode/EIS raster scan observations of the plage region
taken during the gradual phase of the GOES X3.2 flare that occurred on
2006 December 13. The plage region is located 200" east of the flare
arcade. The plage region has a small transient coronal hole. The
transient coronal hole is strongly affected by an X-class flare,
and upflows are observed at its boundary. Multi-wavelength spectral
observations allow us to determine velocities from the Doppler shifts
at different temperatures. Strong upflows along with stationary plasma
have been observed in the FeXV line 284.2Å (log T / K = 6.3) in the
plage region. The strong upflows reach almost 150kms<SUP>-1</SUP>, which
was estimated by a two-component Gaussian fitting. On the other hand,
at a lower corona/transition region temperature (HeII, 256.3Å, log T /
K = 4.9), very weak upflows, almost stationary, have been observed. We
find that these upflow velocities clearly depend on the temperature
with the hottest line, FeXV, showing the fastest upflow velocity and the
second-highest line, FeXIV, showing the second-highest upflow velocity
(130kms<SUP>-1</SUP>). All velocities are below the sound speed. The
trend of the upflow dependence on temperature dramatically changes
at 1MK. These results suggest that heating may have an important role
for strong upflow.
---------------------------------------------------------
Title: Coronal Dimming Observed with Hinode: Outflows Related to a
Coronal Mass Ejection
Authors: Harra, Louise K.; Hara, Hirohisa; Imada, Shinsuke; Young,
Peter R.; Williams, David R.; Sterling, Alphonse C.; Korendyke,
Clarence; Attrill, Gemma D. R.
2007PASJ...59S.801H Altcode:
Coronal dimming has been a signature used to determine the source
of plasma that forms part of a coronal mass ejection (CME) for many
years. Generally dimming is detected through imaging instruments such
as SOHO EIT by taking difference images. Hinode tracked active region
10930 from which there were a series of flares. We combined dimming
observations from EIT with Hinode data to show the impact of flares
and coronal mass ejections on the region surrounding the flaring
active region, and we discuss evidence that the eruption resulted in
a prolonged steady outflow of material from the corona. The dimming
region shows clear structure with extended loops whose footpoints are
the source of the strongest outflow (≈ 40 kms<SUP>-1</SUP>). This
confirms that the loops that are disrupted during the event do lose
plasma and hence are likely to form part of the CME. This is the
first time the velocity of the coronal plasma has been measured in an
extended dimming region away from the flare core. In addition there
was a weaker steady outflow from extended, faint loops outside the
active region before the eruption, which is also long lasting. These
were disturbed and the velocity increased following the flare. Such
outflows could be the source of the slow solar wind.
---------------------------------------------------------
Title: New Evidence for the Role of Emerging Flux in a Solar
Filament's Slow Rise Preceding Its CME-producing Fast Eruption
Authors: Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.
2007ApJ...669.1359S Altcode:
We observe the eruption of a large-scale (~300,000 km) quiet-region
solar filament leading to an Earth-directed “halo” coronal mass
ejection (CME), using data from EIT, CDS, MDI, and LASCO on SOHO
and from SXT on Yohkoh. Initially the filament shows a slow (~1 km
s<SUP>-1</SUP> projected against the solar disk) and approximately
constant velocity rise for about 6 hr, before erupting rapidly, reaching
a velocity of ~8 km s<SUP>-1</SUP> over the next ~25 minutes. CDS
Doppler data show Earth-directed filament velocities ranging from
<20 km s<SUP>-1</SUP> (the noise limit) during the slow-rise phase,
to ~100 km s<SUP>-1</SUP> early in the eruption. Beginning within 10
hr prior to the start of the slow rise, localized new magnetic flux
emerged near one end of the filament. Near the start of and during the
slow-rise phase, soft X-ray (SXR) microflaring occurred repeatedly at
the flux-emergence site, and the magnetic arcade over the filament
progressively brightened in a fan of illumination in SXRs. These
observations are consistent with “tether-weakening” reconnection
occurring between the newly emerging flux and the overlying arcade
field containing the filament, and apparently this reconnection is the
cause of the filament's slow rise. We cannot, however, discern whether
the transition from slow rise to fast eruption was caused by a final
episode of tether-weakening reconnection, or by one or some combination
of other possible mechanisms allowed by the observations. Intensity
“dimmings” and “brightenings” occurring both near to and relatively
far from the location of the filament are possible signatures of the
expansion (“opening”) of the erupting field and its reconnection
with overarching field during the eruption.
---------------------------------------------------------
Title: Solar Origins of Interplanetary Coronal Mass Ejections
Authors: Harra, L. K.
2007ASPC..369..511H Altcode:
Understanding the sources of interplanetary coronal mass ejections
(ICMEs) is a vital element of understanding the workings of our solar
system. In this paper we review the characteristics of ICMEs and
their sources.
---------------------------------------------------------
Title: Coronal “wave”: A signature of the mechanism making CMEs
large-scale in the low corona?
Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.;
Démoulin, P.; Wülser, J. -P.
2007AN....328..760A Altcode:
We analyse one of the first coronal waves observed by STEREO/EUVI
associated with a source region just behind the limb, NOAA 10940. We
apply the coronal “wave” model proposed by Attrill et al. (2007) to
explain the evolution of the observed bright fronts, thereby arguing
that the bright fronts and dimmings are due to magnetic reconnections
between the expanding CME core and surrounding magnetic structures. We
offer a discussion showing that this model provides a mechanism via
which CMEs, expanding from a small source region can naturally become
large-scale in the low corona.
---------------------------------------------------------
Title: How Does Large Flaring Activity from the Same Active Region
Produce Oppositely Directed Magnetic Clouds?
Authors: Harra, Louise K.; Crooker, Nancy U.; Mandrini, Cristina H.;
van Driel-Gesztelyi, Lidia; Dasso, Sergio; Wang, Jingxiu; Elliott,
Heather; Attrill, Gemma; Jackson, Bernard V.; Bisi, Mario M.
2007SoPh..244...95H Altcode:
We describe the interplanetary coronal mass ejections (ICMEs) that
occurred as a result of a series of solar flares and eruptions from
4 to 8 November 2004. Two ICMEs/magnetic clouds occurring from these
events had opposite magnetic orientations. This was despite the fact
that the major flares related to these events occurred within the same
active region that maintained the same magnetic configuration. The solar
events include a wide array of activities: flares, trans-equatorial
coronal loop disappearance and reformation, trans-equatorial filament
eruption, and coronal hole interaction. The first major ICME/magnetic
cloud was predominantly related to the active region 10696 eruption. The
second major ICME/magnetic cloud was found to be consistent with the
magnetic orientation of an erupting trans-equatorial filament or else
a rotation of 160° of a flux rope in the active region. We discuss
these possibilities and emphasize the importance of understanding the
magnetic evolution of the solar source region before we can begin to
predict geoeffective events with any accuracy.
---------------------------------------------------------
Title: Solar Trans-equatorial Activity
Authors: Wang, Jingxiu; Zhang, Yuzong; Zhou, Guiping; Harra, Louise
K.; Williams, David R.; Jiang, Yunchun
2007SoPh..244...75W Altcode:
We have found that solar flares in NOAA active region (AR) 10696 were
often associated with large-scale trans-equatorial activities. These
trans-equatorial activities appeared to be very common and manifest
themselves through i) the formation and eruption of trans-equatorial
loops (TELs), ii) the formation and eruption of trans-equatorial
filaments (TEFs), and iii) the trans-equatorial brightening (TEB) in
the chromosphere. It is determined that the TEF was formed following
episodic plasma ejecta from flares occurring in the AR. The TEF eruption
was associated with a trans-equatorial flare. All flares in the AR that
were accompanied by trans-equatorial activities were associated with
halo coronal mass ejections (CMEs). It was noticed that one or several
major flares in the AR were followed by an increase of brightness
and nonpotentiality of a TEL. These coupled events had a lifetime of
more than 12 hours. In addition their associated halo CMEs always had
a positive acceleration, indicating prolonged magnetic reconnections
in the outer corona at high altitudes.
---------------------------------------------------------
Title: Data Archive of the Hinode Mission
Authors: Matsuzaki, K.; Shimojo, M.; Tarbell, T. D.; Harra, L. K.;
Deluca, E. E.
2007SoPh..243...87M Altcode:
All of the Hinode telemetry data are to be reformatted and archived
in the DARTS system at ISAS and mirrored to data centers around
the word. The archived data are distributed to users through the
Internet. This paper gives an overview of the files in the archive,
including the file formats. All formats are portable and have
heritage from the previous missions. From the reformatted files, index
information is created for faster data search. Users can perform queries
based on information contained in the index. This allows for searches
to return observations that conform to particular observing conditions.
---------------------------------------------------------
Title: The EUV Imaging Spectrometer for Hinode
Authors: Culhane, J. L.; Harra, L. K.; James, A. M.; Al-Janabi, K.;
Bradley, L. J.; Chaudry, R. A.; Rees, K.; Tandy, J. A.; Thomas, P.;
Whillock, M. C. R.; Winter, B.; Doschek, G. A.; Korendyke, C. M.;
Brown, C. M.; Myers, S.; Mariska, J.; Seely, J.; Lang, J.; Kent,
B. J.; Shaughnessy, B. M.; Young, P. R.; Simnett, G. M.; Castelli,
C. M.; Mahmoud, S.; Mapson-Menard, H.; Probyn, B. J.; Thomas, R. J.;
Davila, J.; Dere, K.; Windt, D.; Shea, J.; Hagood, R.; Moye, R.; Hara,
H.; Watanabe, T.; Matsuzaki, K.; Kosugi, T.; Hansteen, V.; Wikstol, Ø.
2007SoPh..243...19C Altcode:
The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona
and upper transition region emission lines in the wavelength ranges
170 - 210 Å and 250 - 290 Å. The line centroid positions and profile
widths will allow plasma velocities and turbulent or non-thermal line
broadenings to be measured. We will derive local plasma temperatures and
densities from the line intensities. The spectra will allow accurate
determination of differential emission measure and element abundances
within a variety of corona and transition region structures. These
powerful spectroscopic diagnostics will allow identification
and characterization of magnetic reconnection and wave propagation
processes in the upper solar atmosphere. We will also directly study
the detailed evolution and heating of coronal loops. The EIS instrument
incorporates a unique two element, normal incidence design. The optics
are coated with optimized multilayer coatings. We have selected highly
efficient, backside-illuminated, thinned CCDs. These design features
result in an instrument that has significantly greater effective area
than previous orbiting EUV spectrographs with typical active region
2 - 5 s exposure times in the brightest lines. EIS can scan a field
of 6×8.5 arc min with spatial and velocity scales of 1 arc sec and
25 km s<SUP>−1</SUP> per pixel. The instrument design, its absolute
calibration, and performance are described in detail in this paper. EIS
will be used along with the Solar Optical Telescope (SOT) and the X-ray
Telescope (XRT) for a wide range of studies of the solar atmosphere.
---------------------------------------------------------
Title: The Hinode (Solar-B) Mission: An Overview
Authors: Kosugi, T.; Matsuzaki, K.; Sakao, T.; Shimizu, T.; Sone,
Y.; Tachikawa, S.; Hashimoto, T.; Minesugi, K.; Ohnishi, A.; Yamada,
T.; Tsuneta, S.; Hara, H.; Ichimoto, K.; Suematsu, Y.; Shimojo, M.;
Watanabe, T.; Shimada, S.; Davis, J. M.; Hill, L. D.; Owens, J. K.;
Title, A. M.; Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Golub, L.
2007SoPh..243....3K Altcode:
The Hinode satellite (formerly Solar-B) of the Japan Aerospace
Exploration Agency's Institute of Space and Astronautical Science
(ISAS/JAXA) was successfully launched in September 2006. As the
successor to the Yohkoh mission, it aims to understand how magnetic
energy gets transferred from the photosphere to the upper atmosphere
and results in explosive energy releases. Hinode is an observatory
style mission, with all the instruments being designed and built to
work together to address the science aims. There are three instruments
onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer
(EIS), and the X-Ray Telescope (XRT). This paper provides an overview
of the mission, detailing the satellite, the scientific payload, and
operations. It will conclude with discussions on how the international
science community can participate in the analysis of the mission data.
---------------------------------------------------------
Title: Hinode Euv Study Of Jets In The Sun’s South Polar Corona
Authors: Culhane, J. L.; Brooks, D. H.; Doschek, G. A.; Harra, L. K.;
van Driel-Gesztelyi, L.; Baker, D.; Lundquist, L. L.; Hansteen, V. H.;
Kamio, S.
2007AAS...210.7201C Altcode: 2007BAAS...39..178C
Using the Hinode EUV Imaging Spectrometer coronal jets were observed
on 20-JAN-2007 over a range of emission lines and corresponding plasma
temperatures using the 40 arc sec wide slot images. In this preliminary
analysis, jet plasma temperature and emissivity have been estimated
while, based on assumptions about the jet morphology, electron density
estimates are given and jet velocity measured. The evolution of the
jets will be followed in a number of different EUV emission lines and
jet energy input as a function of time will be assessed with reference
to the magnetic field topologies involved.
---------------------------------------------------------
Title: Coronal dimming observed with Hinode
Authors: Harra, Louise; Hara, H.; Young, P.; Williams, D.; Sterling,
A.; Attrill, G.
2007AAS...210.6305H Altcode: 2007BAAS...39..172H
Coronal dimming has been a technique used to determine the source
of plasma that forms part of a coronal mass ejection. Generally
dimming is detected through imaging instruments such as SOHO EIT by
taking difference images. In a few cases the SOHO-CDS has been used
to determine outflowing material, and a decrease in density. Hinode
tracked active region 10930 from which there were a series of flares. We
combine dimming observations from EIT with Hinode data to show the
impact of flares and coronal mass ejections on the region surrounding
the flaring active region, and we discuss evidence that the eruption
resulted in a prolonged steady outflow of material from the corona.
---------------------------------------------------------
Title: EIS/Hinode Look At Active Region Dynamics
Authors: Ugarte-Urra, Ignacio; Warren, H. P.; Brooks, D. H.; Williams,
D. R.; Cirtain, J. W.; McKenzie, D. E.; Weber, M.; Hara, H.; Harra,
L. K.
2007AAS...210.9429U Altcode: 2007BAAS...39..222U
We present some initial results from the Hinode EUV Imaging Spectrometer
(EIS) on the heating and cooling of active region loops. The events
we observe are part of the short term active region evolution within
the span of 50 hours of sit-and-stare observations. We investigate
the temporal evolution of the intensity and Doppler shift of spectral
lines formed at different temperatures. We then determine time lags
and cooling times at various temperature regimes and discuss the
results in the context of previous results provided by earlier space
missions. This effort is considered a first step into the hydrodynamic
modeling of the loop structures. The morphology of the structures is
obtained from X-Ray Telescope (XRT) and TRACE images.
---------------------------------------------------------
Title: A Long-duration Flare Observed With Hinode EIS
Authors: Hara, Hirohisa; Watanabe, T.; Harra, L.; Culhane, L.; Cargill,
P.; Doschek, G.; Mariska, J.
2007AAS...210.6802H Altcode: 2007BAAS...39..175H
Long-duration solar flares generally have a cusp apex at the loop
top. The cusp shape reflects the topology of magnetic fields near
the flare-loop top and it is one of the indirect pieces of evidence
supporting the occurrence of the magnetic reconnection process above
flare loops. The Hinode EUV Imaging Spectrometer (EIS) observed a
long-duration flare that occurred on 2006 Dec 17. We present the first
EIS spectroscopic observation of cusp-shaped flare loops. We also
report velocity fields around the cusp structures and post-flare loops.
---------------------------------------------------------
Title: Coronal "wave": Magnetic Footprint Of A Cme?
Authors: Attrill, Gemma; Harra, L. K.; van Driel-Gesztelyi, L.;
Demoulin, P.; Wuelser, J.
2007AAS...210.2921A Altcode: 2007BAAS...39..141A
We propose a new mechanism for the generation of "EUV coronal
waves". This work is based on new analysis of data from SOHO/EIT,
SOHO/MDI & STEREO/EUVI. Although first observed in 1997, the
interpretation of coronal waves as flare-induced or CME-driven remains
a debated topic. We investigate the properties of two "classical"
SOHO/EIT coronal waves in detail. The source regions of the associated
CMEs possess opposite helicities & the coronal waves display
rotations in opposite senses. We observe deep dimmings near the
flare site & also widespread diffuse dimming, accompanying the
expansion of the EIT wave. We report a new property of these EIT
waves, namely, that they display dual brightenings: persistent ones
at the outermost edge of the core dimming regions & simultaneously
diffuse brightenings constituting the leading edge of the coronal wave,
surrounding the expanding diffuse dimmings. We show that such behaviour
is consistent with a diffuse EIT wave being the magnetic footprint of
a CME. We propose a new mechanism where driven magnetic reconnections
between the skirt of the expanding CME & quiet-Sun magnetic loops
generate the observed bright diffuse front. The dual brightenings &
widespread diffuse dimming are identified as innate characteristics
of this process. In addition we present some of the first analysis
of a STEREO/EUVI limb coronal wave. We show how the evolution of the
diffuse bright front & dimmings can be understood in terms of the
model described above. We show that an apparently stationary part of
the bright front can be understood in terms of magnetic interchange
reconnections between the expanding CME & the "open" magnetic
field of a low-latitude coronal hole. We use both the SOHO/EIT &
STEREO/EUVI events to demonstrate that through successive reconnections,
this new model provides a natural mechanism via which CMEs can become
large-scale in the lower corona.
---------------------------------------------------------
Title: Iron Line Ratio Analysis in an Active Region
Authors: Watanabe, Tetsuya; Hara, H.; Culhane, J. L.; Harra, L. K.;
Doschek, G. A.; Mariska, J. T.; Young, P. R.; Hinode EIS Team
2007AAS...210.7204W Altcode: 2007BAAS...39..179W
Increased diagnostic capability of the EIS instrument on board Hinode
(Solar-B) is demonstrated with a set of iron emission lines appearing
in the two EIS observing wavelengths (170 - 210 A & 250 - 290
A) and their line intensity ratios. First-light spectra of a small
active region show iron lines at the ionization stages of FeVIII
(185.2 A & 186.6 A) through FeXVII (204.7 A, 254.9 A, & 269.4
A). Decay phase spectra of a C-class flare confirms the presence of
this higher temperature line; FeXVII at 254.9 A more clearly, as well
as those lines of flare temperatures; FeXXIV (192.0 A & 255.1 A)
and FeXXIII (263.8 A).
---------------------------------------------------------
Title: Coronal Magnetic Connectivity and EUV Dimmings
Authors: Zhang, Yuzong; Wang, Jingxiu; Attrill, Gemma D. R.; Harra,
Louise K.; Yang, Zhiliang; He, Xiangtao
2007SoPh..241..329Z Altcode:
Coronal dimming can be considered to be a disk signature of
front-side coronal mass ejections (CMEs) (Thompson et al.: 2000,
Geophys. Res. Lett.27, 1431). The study of the magnetic connectivity
associated with coronal dimming can shed new light on the magnetic
nature of CMEs. In this study, four major flare-CME events on 14
July 2000, 28 October 2003, 7 November 2004, and 15 January 2005 are
analyzed. They were all halo CMEs associated with major flare activity
in complex active regions (ARs) and produced severe space weather
consequences. To explore the magnetic connectivity of these CMEs,
global potential-field extrapolations based on the composite synoptic
magnetograms from the Michelson Doppler Imager onboard the Solar
and Heliospheric Observatory are constructed, and their association
with coronal dimming is revealed by the Extreme ultraviolet Imaging
Telescope. It is found that each flare-CME event involved interaction of
more than ten sets of magnetic-loop systems. These loop systems occupied
over 50% of all identified loop systems in the visible hemisphere and
covered a wide range of solar longitudes and latitudes. We categorize
the loop systems as active-region loops (ARLs), AR-interconnecting loops
(ARILs) including transequatorial loops (TLs), and long arcades (LAs)
straddling filament channels. A recurring pattern, the saddle-field
configuration (SFC), consisting of ARILs, is found to be present in
all four major flare-CME events. The magnetic connectivity revealed
by this work implies that intercoupling and interaction of multiple
flux-loop systems are required for a major CME. For comparison, a
simple flare-CME event of 12 May 1997 with a relatively simple magnetic
configuration is chosen. Even for this simple flare-CME event, we find
that multiple flux-loop systems are also present.
---------------------------------------------------------
Title: A Multiple Flare Scenario where the Classic Long-Duration
Flare Was Not the Source of a CME
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Culhane,
J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.;
Kurokawa, H.
2007SoPh..240..283G Altcode:
A series of flares (GOES class M, M and C) and a CME were observed in
close succession on 20 January 2004 in NOAA 10540. Radio observations,
which took the form of types II, III and N bursts, were associated with
these events. We use the combined observations from TRACE, EIT, Hα
images from Kwasan, MDI magnetograms and GOES to understand the complex
development of this event. Contrary to a standard interpretation,
we conclude that the first two impulsive flares are part of the CME
launch process while the following long-duration event flare represents
simply the recovery phase. Observations show that the flare ribbons
not only separate but also shift along the magnetic inversion line
so that magnetic reconnection progresses stepwise to neighboring flux
tubes. We conclude that "tether cutting" reconnection in the sheared
arcade progressively transforms it to a twisted flux tube, which
becomes unstable, leading to a CME. We interpret the third flare,
a long-duration event, as a combination of the classical two-ribbon
flare with the relaxation process following forced reconnection between
the expanding CME structure and neighboring magnetic fields.
---------------------------------------------------------
Title: Decametric N Burst: A Consequence of the Interaction of Two
Coronal Mass Ejections
Authors: Démoulin, P.; Klein, K. -L.; Goff, C. P.; van
Driel-Gesztelyi, L.; Culhane, J. L.; Mandrini, C. H.; Matthews, S. A.;
Harra, L. K.
2007SoPh..240..301D Altcode:
Radio emissions of electron beams in the solar corona and interplanetary
space are tracers of the underlying magnetic configuration and of
its evolution. We analyse radio observations from the Culgoora and
WIND/WAVES spectrographs, in combination with SOHO/LASCO and SOHO/MDI
data, to understand the origin of a type N burst originating from NOAA
AR 10540 on January 20, 2004, and its relationship with type II and
type III emissions. All bursts are related to the flares and the CME
analysed in a previous paper (Goff et al., 2007). A very unusual feature
of this event was a decametric type N burst, where a type III-like
burst, drifting towards low frequencies (negative drift), changes drift
first to positive, then again to negative. At metre wavelengths, i.e.,
heliocentric distances ≲1.5R<SUB>⊙</SUB>, these bursts are ascribed
to electron beams bouncing in a closed loop. Neither U nor N bursts are
expected at decametric wavelengths because closed quasi-static loops
are not thought to extend to distances ≫1.5R<SUB>⊙</SUB>. We take
the opportunity of the good multi-instrument coverage of this event to
analyse the origin of type N bursts in the high corona. Reconnection
of the expanding ejecta with the magnetic structure of a previous CME,
launched about 8 hours earlier, injects electrons in the same manner as
with type III bursts but into open field lines having a local dip and
apex. The latter shape was created by magnetic reconnection between
the expanding CME and neighbouring (open) streamer field lines. This
particular flux tube shape in the high corona, between 5R<SUB>⊙</SUB>
and 10R<SUB>⊙</SUB>, explains the observed type N burst. Since the
required magnetic configuration is only a transient phenomenon formed
by reconnection, severe timing and topological constraints are present
to form the observed decametric N burst. They are therefore expected
to be rare features.
---------------------------------------------------------
Title: Coronal “Wave”: Magnetic Footprint of a Coronal Mass
Ejection?
Authors: Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi,
Lidia; Démoulin, Pascal
2007ApJ...656L.101A Altcode:
We investigate the properties of two “classical” EUV Imaging Telescope
(EIT) coronal waves. The two source regions of the associated coronal
mass ejections (CMEs) possess opposite helicities, and the coronal waves
display rotations in opposite senses. We observe deep core dimmings
near the flare site and also widespread diffuse dimming, accompanying
the expansion of the EIT wave. We also report a new property of these
EIT waves, namely, that they display dual brightenings: persistent ones
at the outermost edge of the core dimming regions and simultaneously
diffuse brightenings constituting the leading edge of the coronal wave,
surrounding the expanding diffuse dimmings. We show that such behavior
is consistent with a diffuse EIT wave being the magnetic footprint of
a CME. We propose a new mechanism where driven magnetic reconnections
between the skirt of the expanding CME magnetic field and quiet-Sun
magnetic loops generate the observed bright diffuse front. The dual
brightenings and the widespread diffuse dimming are identified as
innate characteristics of this process.
---------------------------------------------------------
Title: EUI, The Ultraviolet Imaging Telescopes Of Solar Orbiter
Authors: Hochedez, J. -F.; Appourchaux, T.; Defise, J. -M.; Harra,
L. K.; Schühle, U.; Auchère, F.; Curdt, W.; Hancock, B.; Kretzschmar,
M.; Lawrence, G.; Leclec'h, J. -C.; Marsch, E.; Mercier, R.; Parenti,
S.; Podladchikova, E.; Ravet, M. -F.; Rochus, P.; Rodriguez, L.;
Rouesnel, F.; Solanki, S.; Teriaca, L.; Van Driel, L.; Vial, J. -C.;
Winter, B.; Zhukov, A.
2007ESASP.641E..33H Altcode:
The scientific objectives of Solar Orbiter rely ubiquitously on EUI,
its suite of solar atmosphere imaging telescopes. In the configuration
discussed here, EUI includes three co-aligned High Resolution Imagers
(HRI) and one Full Sun Imager (FSI). FSI and two HRIs observe in extreme
ultraviolet passbands, dominated by coronal emission. Another HRI is
designed for the hydrogen Lyman α radiation in the far UV, imaging the
Chromosphere and the lower Transition Region. The current EUI design
and some of its development challenges are highlighted. EUI profits from
co-rotation phases, solar proximity and departure from the ecliptic. In
synergy with the other S.O. payload, EUI probes the dynamics of the
solar atmosphere, provides context data for all investigations and helps
to link in-situ and remote-sensing observations. In short, it serves all
four top-level goals of the mission. For these reasons, the EUI suite
is keenly anticipated in the European scientific community and beyond.
---------------------------------------------------------
Title: Coronal Mass Ejection
Authors: Cargill, P. J.; Harra, L. K.
2007hste.book..118C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar flares: the observations
Authors: Harra, Louise K.
2007MmSAI..78..236H Altcode:
The understanding of solar flares has progressed enormously in the
past decades. There is now strong observational evidence that magnetic
reconnection is occurring. I will discuss the observational indicators
of reconnection - and also the areas where the observations contradict
the theory. The actual trigger for flares is not well understood and I
will discuss how observations from the recently launched Hinode space
mission will be able to address this problem.
---------------------------------------------------------
Title: Using the Evolution of Coronal Dimming Regions to Probe the
Global Magnetic Field Topology
Authors: Attrill, G.; Nakwacki, M. S.; Harra, L. K.; Van
Driel-Gesztelyi, L.; Mandrini, C. H.; Dasso, S.; Wang, J.
2006SoPh..238..117A Altcode: 2006SoPh..tmp...31A
We demonstrate that study of the evolving magnetic nature of coronal
dimming regions can be used to probe the large-scale magnetic structure
involved in the eruption of a coronal mass ejection (CME). We analyse
the intensity evolution of coronal dimming regions using 195 Å data
from the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar
and Heliospheric Observatory (SOHO). We measure the magnetic flux, using
data from the SOHO/Michelson Doppler Imager (MDI), in the regions that
seem most likely to be related to plasma removal. Then, we compare these
magnetic flux measurements to the flux in the associated magnetic cloud
(MC). Here, we present our analysis of the well-studied event on 12
May 1997 that took place just after solar minimum in a simple magnetic
configuration. We present a synthesis of results already published and
propose that driven "interchange reconnection" between the expanding
CME structure with “open” field lines of the northern coronal hole
region led to the asymmetric temporal and spatial evolution of the
two main dimming regions, associated with this event. As a result of
this reconnection process, we find the southern-most dimming region
to be the principal foot-point of the MC. The magnetic flux from this
dimming region and that of the MC are found to be in close agreement
within the same order of magnitude, 10<SUP>21</SUP> Mx.
---------------------------------------------------------
Title: The extreme UV imaging spectrometer for the JAXA Solar-B
mission
Authors: Culhane, J. L.; Doschek, G. A.; Watanabe, T.; Smith, A.;
Brown, C.; Hara, H.; Harra, L. K.; James, A. M.; al Janabi, K.;
Kent, B.; Korendyke, C.; Lang, J.; Mariska, J.; Myers, S.; Seely,
J.; Simnett, G.; Tandy, J.; Thomas, R.; Windt, D. L.
2006SPIE.6266E..0TC Altcode: 2006SPIE.6266E..22C
The ISAS/JAXA Solar-B mission includes an Extreme-UV Imaging
Spectrometer (EIS). It detects photons in the wavelength ranges 17 -
21 nm and 25 - 29 nm which include emission lines from several highly
ionised species that exist at temperatures log T = 4.7, 5.6, 5.8,
5.9 and 6.0 - 7.3 K. Instrument throughput is increased substantially
by the use of multilayer coatings optimized for maximum reflectance
in the two selected wavelength bands. The use of back-illuminated
CCDs provides significantly enhanced quantum efficiency over that
previously available from microchannel plate systems. In this paper we
will describe the design and operation of the instrument and present
its performance parameters e.g. spectral and spatial resolution and
sensitivity. Preliminary results of recent calibration measurements
will be described. The role of EIS in the Solar-B mission will be
illustrated with reference to the anticipated observing strategy for
the first three months of the mission which will be outlined.
---------------------------------------------------------
Title: Initiation of the Slow-Rise and Fast-Rise Phases of an Erupting
Solar Filamentby Localized Emerging Magnetic Field via Microflaring
Authors: Sterling, Alphonse C.; Moore, R. L.; Harra, L. K.
2006SPD....37.0823S Altcode: 2006BAAS...38..234S
EUV data from EIT show that a filament of 2001 February 28 underwent
aslow-rise phase lasting about 6 hrs, before rapidly erupting in a
fast-risephase. Concurrent images in soft X-rays (SXRs) from Yohkoh/SXT
show that aseries of three microflares, prominent in SXT images but weak
in EIT 195 AngEUV images, occurred near one end of the filament. The
first and lastmicroflares occurred respectively in conjunction with
the start of theslow-rise phase and the start of the fast-rise phase,
and the second microflarecorresponded to a kink in the filament
trajectory. Beginning within 10 hoursof the start of the slow rise,
new magnetic flux emerged at the location of themicroflaring. This
localized new flux emergence and the resulting microflares,consistent
with reconnection between the emerging field and the sheared sigmoidcore
magnetic field holding the filament, apparently caused the slow
rise ofthis field and the transition to explosive eruption. For the
first time insuch detail, the observations show this direct action of
localized emergingflux in the progressive destabilization of a sheared
core field in the onset ofa coronal mass ejection (CME). Similar
processes may have occurred in otherrecently-studied events.NASA
supported this work through NASA SR&T and SEC GI grants.
---------------------------------------------------------
Title: Transequatorial Filament Eruption and Its Link to a Coronal
Mass Ejection
Authors: Wang, Jing-Xiu; Zhou, Gui-Ping; Wen, Ya-Yuan; Zhang, Yu-Zong;
Wang, Hua-Ning; Deng, Yuan-Yong; Zhang, Jun; Harra, Louise K.
2006ChJAA...6..247W Altcode:
We revisit the Bastille Day flare/CME Event of 2000 July 14, and
demonstrate that this flare/CME event is not related to only one single
active region (AR). Activation and eruption of a huge transequatorial
filament are seen to precede the simultaneous filament eruption and
flare in the source active region, NOAA AR 9077, and the full halo-CME
in the high corona. Evidence of reconfiguration of large-scale magnetic
structures related to the event is illustrated by SOHO EIT and Yohkoh
SXT observations, as well as, the reconstructed 3D magnetic lines
of force based on the force-free assumption. We suggest that the AR
filament in AR 9077 was connected to the transequatorial filament. The
large-scale magnetic composition related to the transequatorial filament
and its sheared magnetic arcade appears to be an essential part of the
CME parent magnetic structure. Estimations show that the filament-arcade
system has enough magnetic helicity to account for the helicity carried
by the related CMEs. In addition, rather global magnetic connectivity,
covering almost all the visible range in longitude and a huge span in
latitude on the Sun, is implied by the Nançay Radioheliograph (NRH)
observations. The analysis of the Bastille Day event suggests that
although the triggering of a global CME might take place in an AR,
a much larger scale magnetic composition seems to be the source of
the ejected magnetic flux, helicity and plasma. The Bastille Day
event is the first described example in the literature, in which a
transequatorial filament activity appears to play a key role in a
global CME. Many tens of halo-CME are found to be associated with
transequatorial filaments and their magnetic environment.
---------------------------------------------------------
Title: Connecting the Sun to the Earth
Authors: Harra, L.; Owen, C.
2006Obs...126...78H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-thermal broadening of coronal emission lines in the onset
phase of solar flares and CMEs
Authors: Kay, H. R. M.; Matthews, S. A.; Harra, L. K.; Culhane, J. L.
2006A&A...447..719K Altcode:
The non-thermal broadening of soft X-ray emission lines is commonly seen
during the early stages of solar flares and is thought to be associated
with either the initial flare energy release or the evaporation of
chromospheric plasma. Here we investigate the magnitude of non-thermal
broadening for a sample of 12 flares associated with both eruptive and
non-eruptive events, i.e. those with and without associated coronal mass
ejections (CMEs), using the Bragg Crystal Spectrometer (BCS) on the
Yohkoh spacecraft. The maximum non-thermal broadening of the eruptive
flares was found to be on average lower than for the flares which were
not associated with CMEs. There was no evidence of any relationship
between the maximum non-thermal broadening and the initial CME speed.
---------------------------------------------------------
Title: Observations of Coronal Mass Ejections
Authors: Harra, Louise K.; Wang, Jingxiu
2006IAUS..233..455H Altcode:
Observations of source regions of coronal mass ejections have
progressed enormously in the past decade with the observations from
SOHO and Yohkoh. Progress has been made on understanding magnetic
helicity, coronal dimming, coronal waves and flares in terms of
their relationship to CMEs. Observations have been used to verify and
disagree with models such as tether-cutting, kink instabilities and
the breakout model. We will describe the observations, recent models,
and how future observations from the Solar-B and STEREO missions will
address many unanswered questions.
---------------------------------------------------------
Title: Combined analysis of the 15-16 May, 1997, magnetic cloud and
of its solar source region
Authors: Nakwacki, M. S.; Atrill, G.; Dasso, S.; Mandrini, C. H.;
van Driel-Gesztelyi, L.; Harra, L.; Wang, J.
2006BAAA...49...46N Altcode:
In this work we analise the structure of the magnetic cloud (MC)
observed by Wind between 15-16 May 1997, and the related solar
event, a long duration C1.3 flare which ocurred on 12 May 1997. This
event presented two dark regions in EUV (dimmings) with asymmetric
evolution. The magnetic structure of the MC was modeled using three
cylindrical helicoidal models, considering the asymmetry between its
front and its final part. We calculate the magnetic flux in the dimmings
and their evolution, and the flux through the surface perpendicular to
the cloud axis and to the azimuthal direction. Finally, we compare the
total flux of both, MC and dimmings, and propose a topological model
for the solar event. FULL TEXT IN SPANISH
---------------------------------------------------------
Title: A combined analysis of the magnetic cloud on 15-16 May 1997
and its solar source region
Authors: Nakwacki, M. S.; Attrill, G.; Dasso, S.; Mandrini, C. H.;
van Driel-Gesztelyi, L.; Harra, L. K.; Wang, J.
2006cosp...36.2479N Altcode: 2006cosp.meet.2479N
Coronal Mass Ejections CMEs are the most important short-lived agents
that transport magnetic flux from the Sun to the interplanetary medium
Thus detailed studies of the solar sources of CMEs and the associated
magnetic clouds MCs are an important key to understand and constrain
solar and interplanetary models We analyze the magnetic structure of the
MC observed on 15-16 May 1997 by the spacecraft Wind and its associated
solar event a C1 3 long duration event that occurred on 12 May 1997 in
AR8038 Two main dimming regions that exhibit an asymmetric temporal
and spatial evolution were observed in association with this event
We compute the magnetic flux in the dimmings and follow its evolution
using magnetograms from the Michelson Doppler Imager SoHO MDI The MC
structure is inferred using three different helical cylindrical models
with a significantly different radial twist distribution We also take
into account the asymmetry observed between the front and the rear
part of the cloud We fit the free parameters of each model comparing
models with in situ observations Then we estimate the flux across the
surface perpendicular to the axis of the cylinder and the flux across
the surface formed by this axis and the cloud radial direction Finally
we compare the MC total flux with that corresponding to both observed
dimmings By combining our interplanetary measurements and the dimmings
flux evolution we propose a topological model for the 12 May eruptive
event We discuss the constrains set by solar observations on
---------------------------------------------------------
Title: Multi-scale reconnections in a complex CME
Authors: van Driel-Gesztelyi, L.; Goff, C.; Demoulin, P.; Culhane,
J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.;
Kurokawa, H.
2006cosp...36.2371V Altcode: 2006cosp.meet.2371V
A series of flares GOES class M M and C and a CME were observed on
20-JAN-2004 occurring in close succession in NOAA 10540 Types II III
and an N radio bursts were associated We use the combined observations
from TRACE EIT H-alpha images from Kwasan Observatory MDI magnetograms
GOES and radio observations from Culgoora and Wind WAVES to understand
the complex development of this event We link the first two impulsive
flares to tether-cutting reconnections and the launch of the CME while
the last of the flares an LDE to the relaxation phase following forced
reconnections between the erupting flux rope and neighbouring magnetic
field lines We show that reconnection with the magnetic structure of
a previous CME launched about 8 hours earlier injects electrons into
open field lines having a local dip and apex of about 6 solar radii
height The dipped shape of these field lines was due to large-scale
magnetic reconnection between expanding magnetic loops and open field
lines of a neighbouring streamer This particular situation explains
the observed decametric N burst and why N-bursts are so rare
---------------------------------------------------------
Title: Large-Scale Magnetic Connectivity in CMEs
Authors: Zhang, Yuzong; Wang, Jingxiu; Attrill, Gemma; Harra, Louise K.
2006IAUS..233..357Z Altcode:
Five flare/CME events were selected in this study. One is on May 12,
1997, for which there is only two active regions on the visible
solar disc, and the magnetic configuration is rather simple. For
other cases, many active regions were visible. They are the flare/CME
events that occurred on Bastille Day of 2000, Oct. 28, 2003, Nov. 7,
2004 and Jan. 20, 2005. By tracing the spread of EUV dimming, which
was obtained by SOHO/EIT 195 Å fixed-difference images, we studied
the CME initiation and development on the solar disc. At the same
time we reconstructed the 3D magnetic structure of coronal magnetic
fields, extrapolated from the observed photospheric magnetograms by
SOHO/MDI. In scrutinizing the EUV brightening and dimming propagation
from CME initiation sites to large areas with different magnetic
connectivities, we determine the overall coupling and interacting of
multiple flux systems in the CME processes. Several typical patterns
of magnetic connectivity are described and discussed in the view of
CME initiation mechanism or mechanisms.
---------------------------------------------------------
Title: The MOSES spectral imager for KuaFu-A
Authors: Harra, L. K.; van Driel-Gesztelyi, L.; Cole, R.; Sun, J.;
Winter, B.; Hancock, B.
2006cosp...36.3670H Altcode: 2006cosp.meet.3670H
We will describe the instrument design for a spectral imager on the
KuaFu mission KuaFu s science goals are aimed at understanding space
weather with a spacecraft located at L1 and 2 spacecraft in a polar
orbit around the Earth The spectral imager will provide crucial
information on the source region of coronal mass ejections It will
achieve this by measuring the Doppler velocities and intensity over
the field of view of the solar activity zone which is geoeffective
This allows us to determine whether activity on the Sun does actually
releases material into the interplanetary medium BEFORE we observe
it in coronagraphs We will summarise the instrument design and the
scientific drivers for it
---------------------------------------------------------
Title: Multi spacecraft observations from the Sun to the Earth
Authors: Harra, L. K.; Smith, A.; Fazakerley, A. N.; Mandrini, C.;
Matthews, S. A.
2005ESASP.588..401H Altcode: 2005tssc.conf..401H
No abstract at ADS
---------------------------------------------------------
Title: a Series of Compact Flares with AN Associated CME
Authors: Goff, C. P.; van Driel-Geszrelyi, L.; Culhane, J. L.;
Matthews, S. A.; Harra, L. K.; Démoulin, P.; Mandrini, C. H.;
Kurokawa, H.
2005ESASP.600E.157G Altcode: 2005ESPM...11..157G; 2005dysu.confE.157G
No abstract at ADS
---------------------------------------------------------
Title: Erupting Flux Rope, Rising X-Ray Source and a Slow CME on 16
April 2002
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews,
S. A.; Mandrini, C. H.
2005ESASP.600E..46G Altcode: 2005ESPM...11...46G; 2005dysu.confE..46G
No abstract at ADS
---------------------------------------------------------
Title: Relating Near-Earth Observations of AN Interplanetary Coronal
Mass Ejection to the Conditions at its Site of Origin in the Solar
Corona
Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van
Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle,
C.; Balogh, A.; Réme, H.
2005ESASP.600E..47F Altcode: 2005dysu.confE..47F; 2005ESPM...11...47F
No abstract at ADS
---------------------------------------------------------
Title: X-Ray Observations of Solar Long-Duration Flares
Authors: Phillips, K. J. H.; Feldman, U.; Harra, L. K.
2005ApJ...634..641P Altcode:
Yohkoh X-ray observations during the several-hour decay of six
large solar flares show that the main emitting region is in the
form of a bright loop-top source whose spatial extent well after
the impulsive stage explains most of the broadening of S XV and Ca
XIX X-ray lines, which would otherwise imply nonthermal velocities
of 100 km s<SUP>-1</SUP> or more. During the decay of each event,
the electron temperature and emission measure decline slowly. For the
nearly disk center event of 1992 February 27, the volume increases and
the deduced lower limit to the electron density N<SUB>e</SUB> decreases
from ~10<SUP>11</SUP> cm<SUP>-3</SUP> to just below 10<SUP>10</SUP>
cm<SUP>-3</SUP>. The nonuniform emission along the loops indicates
that Spitzer heat conduction does not operate. If radiation is the
only or main energy-loss mechanism, the lower limits to N<SUB>e</SUB>
imply upper limits to radiation cooling times of up to 10 hr, less
than the flare decay time, so necessitating a continuing energy
input. Although magnetic reconnection of previous broken open loops
(the Kopp-Pneuman model) has been widely regarded as the source of
energy in such flares, the small nonthermal velocities-only 20-50
km s<SUP>-1</SUP> as indicated by SUMER observations-and the lack of
spectroscopic indicators of large inflows or outflows argue against
it. Other flare models must also explain the relatively small nonthermal
velocities. An alternative picture of loop oscillations recently seen
in TRACE and Yohkoh data is proposed for the production of observed
nonthermal velocities.
---------------------------------------------------------
Title: Magnetic Fields and Intensity Changes in Coronal Dimming
Regions
Authors: Attrill, G. D. R.; Narukage, N.; Shibata, K.; Harra, L. K.
2005ESASP.596E..11A Altcode: 2005ccmf.confE..11A
No abstract at ADS
---------------------------------------------------------
Title: Explosions on the Sun
Authors: Harra, Louise K.
2005aabb.book..375H Altcode:
I will describe the most dynamic and highly energetic phenomena in
the Solar System - these are the eruptions and flaring that occur on
the Sun. They can release as much energy as 10 million volcanoes,
and throw out material into the solar system with similar mass to
Mount Everest! The theories of what can produce such an explosion are
based around the magnetic field that confines the gas. These events
can produce emission right across the electromagnetic spectrum. The
status of our ability to predict these events is discussed.
---------------------------------------------------------
Title: Flows in the solar atmosphere due to the eruptions on the
15th July, 2002
Authors: Harra, L. K.; Démoulin, P.; Mandrini, C. H.; Matthews,
S. A.; van Driel-Gesztelyi, L.; Culhane, J. L.; Fletcher, L.
2005A&A...438.1099H Altcode:
Which kind of flows are present during flares? Are they compatible
with the present understanding of energy release and which model
best describes the observations? We analyze successive flare events
in order to answer these questions. The flares were observed in the
magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One
of them is of GOES X-class. The description of these flares and how
they relate to the break-out model is presented in Gary & Moore
(2004). The Coronal Diagnostic Spectrometer on board SOHO observed
this active region for around 14 h. The observed emission lines
provided data from the transition region to the corona with a field
of view covering more than half of the active region. In this paper
we analyse the spatially resolved flows seen in the atmosphere from
the preflare to the flare stages. We find evidence for evaporation
occurring before the impulsive phase. During the main phase, the
ongoing magnetic reconnection is demonstrated by upflows located at
the edges of the flare loops (while downflows are found in the flare
loops themselves). We also report the impact of a filament eruption
on the atmosphere, with flows up to 300 km s<SUP>-1</SUP> observed at
transition-region temperatures in regions well away from the location
of the pre-eruptive filament. Our results are consistent with the
predictions of the break out model before the impulsive phase of the
flare; while, as the flare progresses, the directions of the flows are
consistent with flare models invoking evaporation followed by cooling
and downward plasma motions in the flare loops.
---------------------------------------------------------
Title: Stability of EUV multilayers to long-term heating, and to
energetic protons and neutrons, for extreme solar missions
Authors: Rousseau, A. D.; Windt, D. L.; Winter, B.; Harra, L.;
Lamoureux, H.; Eriksson, F.
2005SPIE.5900...14R Altcode:
We have systematically investigated the thermal and particle stability
of several state-of-the-art EUV multilayer coatings suitable for use in
high-performance solar instrumentation. Our research has been motivated
principally by the performance requirements for extreme solar missions
such as Solar Orbiter, an approved ESA mission with an expected launch
date of 2013. The goal of this particular mission is to explore the
solar atmosphere with both in situ and remote sensing instrumentation
at a close encounter. At perihelion the mission will reach 0.2
A.U. providing a unique viewpoint where the instruments can both
'see' and 'feel' the dynamic atmosphere. But the orbit is technically
challenging- no remote sensing instrument has been put in such close
proximity to the Sun before. Furthermore, the thermal and particle
environment will not only be severe but will suffer huge fluctuations
as the elliptical orbit changes from 0.2 A.U. to 1.1 A.U. Several of
the remote sensing packages on the strawman payload of the mission
contain multilayer coatings, thus the stability of these coatings to
the expected thermal and particle environment must be established. In
this paper, we investigate the impact on the integrity of several
candidate EUV multilayer coatings after long-term thermal annealing,
and upon exposure to energetic protons and neutrons. In summary,
we find no significant degradation in any of the multilayer samples
tested. These results suggest that the multilayers we have studied
can be safely used for Solar Orbiter or other extreme solar missions.
---------------------------------------------------------
Title: Relating near-Earth observations of an interplanetary coronal
mass ejection to the conditions at its site of origin in the solar
corona
Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van
Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle,
C.; Balogh, A.; Rème, H.
2005GeoRL..3213105F Altcode:
A halo coronal mass ejection (CME) was detected on January 20, 2004. We
use solar remote sensing data (SOHO, Culgoora) and near-Earth in situ
data (Cluster) to identify the CME source event and show that it was a
long duration flare in which a magnetic flux rope was ejected, carrying
overlying coronal arcade material along with it. We demonstrate that
signatures of both the arcade material and the flux rope material are
clearly identifiable in the Cluster and ACE data, indicating that the
magnetic field orientations changed little as the material traveled
to the Earth, and that the methods we used to infer coronal magnetic
field configurations are effective.
---------------------------------------------------------
Title: The first observed stellar X-ray flare oscillation: Constraints
on the flare loop length and the magnetic field
Authors: Mitra-Kraev, U.; Harra, L. K.; Williams, D. R.; Kraev, E.
2005A&A...436.1041M Altcode: 2005astro.ph..3384M
We present the first X-ray observation of an oscillation during
a stellar flare. The flare occurred on the active M-type dwarf
<ASTROBJ>AT Mic</ASTROBJ> and was observed with XMM-Newton. The
soft X-ray light curve (0.2-12 keV) is investigated with wavelet
analysis. The flare's extended, flat peak shows clear evidence for
a damped oscillation with a period of around 750 s, an exponential
damping time of around 2000 s, and an initial, relative peak-to-peak
amplitude of around 15%. We suggest that the oscillation is a standing
magneto-acoustic wave tied to the flare loop, and find that the
most likely interpretation is a longitudinal, slow-mode wave, with a
resulting loop length of (2.5 ± 0.2)×10<SUP>10</SUP> cm. The local
magnetic field strength is found to be 105 ± 50 G. These values are
consistent with (oscillation-independent) flare cooling time models
and pressure balance scaling laws. Such a flare oscillation provides
an excellent opportunity to obtain coronal properties like the size
of a flare loop or the local magnetic field strength for the otherwise
spatially-unresolved star.
---------------------------------------------------------
Title: A slow coronal mass ejection with rising X-ray source
Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews,
S. A.; Mandrini, C. H.
2005A&A...434..761G Altcode:
An eruptive event, which occurred on 16th April 2002, is
discussed. Using images from the Transition Region and Coronal Explorer
(TRACE) at 195 Å, we observe a lifting flux rope which gives rise
to a slow coronal mass ejection (CME). There are supporting velocity
observations from the Coronal Diagnostic Spectrometer (CDS) on the Solar
and Heliospheric Observatory (SOHO), which illustrate the helical nature
of the structure. Additionally a rising coronal hard X-ray source,
which is observed with the Reuven Ramaty High Energy Solar Spectroscopic
Imager (RHESSI), is shown to follow the flux rope with a speed of ~60
km s<SUP>-1</SUP>. It is also sampled by the CDS slit, although it has
no signature in the Fe XIX band. Following the passage of this source,
there is evidence from the CDS for down-flowing (cooling) material
along newly reconnected loops through Doppler velocity observations,
combined with magnetic field modeling. Later, a slow CME is observed
with the Large Angle and Spectroscopic Coronagraph (LASCO). We combine
a height-time profile of the flux rope at lower altitudes with the slow
CME. The rising flux rope speeds up by a factor of 1.7 at the start
of the impulsive energy release and goes through further acceleration
before reaching 1.5 solar radii. These observations support classical
CME scenarios in which the eruption of a filament precedes flaring
activity. Cusped flare loops are observed following the erupting
flux rope and their altitude increases with time. In addition we
find RHESSI sources both below and above the probable location of the
reconnection region.
---------------------------------------------------------
Title: Loop length and magnetic field estimates from oscillations
detected during an X-ray flare on AT Mic
Authors: Mitra-Kraev, U.; Harra, L. K.
2005ESASP.560..821M Altcode: 2005csss...13..821M; 2004astro.ph.10656M
We analyse oscillations observed in the X-ray light curve of
the late-type star AT Mic. The oscillations occurred during flare
maximum. We interpret these oscillations as density perturbations in
the flare loop. Applying various models derived for the Sun, the loop
length and the magnetic field of the flare can be estimated. We find
a period of 740 s, and that the models give similar results (within a
factor of 2) for the loop length (~5.4e10 cm) and the magnetic field
(~100 G). For the first time, an oscillation of a stellar X-ray flare
has been observed and results thus obtained for otherwise unobservable
physical parameters.
---------------------------------------------------------
Title: Relationship between X-ray and ultraviolet emission of flares
from dMe stars observed by XMM-Newton
Authors: Mitra-Kraev, U.; Harra, L. K.; Güdel, M.; Audard, M.;
Branduardi-Raymont, G.; Kay, H. R. M.; Mewe, R.; Raassen, A. J. J.;
van Driel-Gesztelyi, L.
2005A&A...431..679M Altcode: 2004astro.ph.10592M
We present simultaneous ultraviolet and X-ray observations of
the dMe-type flaring stars <ASTROBJ>AT Mic</ASTROBJ>, <ASTROBJ>AU
Mic</ASTROBJ>, <ASTROBJ>EV Lac</ASTROBJ>, <ASTROBJ>UV Cet</ASTROBJ>
and <ASTROBJ>YZ CMi</ASTROBJ> obtained with the XMM-Newton
observatory. During 40 h of simultaneous observation we identify
13 flares which occurred in both wave bands. For the first time,
a correlation between X-ray and ultraviolet flux for stellar flares
has been observed. We find power-law relationships between these two
wavelength bands for the flare luminosity increase, as well as for
flare energies, with power-law exponents between 1 and 2. We also
observe a correlation between the ultraviolet flare energy and the
X-ray luminosity increase, which is in agreement with the Neupert
effect and demonstrates that chromospheric evaporation is taking place.
---------------------------------------------------------
Title: Preface
Authors: Harra, Louise K.
2005AdSpR..36.1359H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: An imager with added value for the Solar Orbiter mission
Authors: Harra, L. K.; Kankelborg, C. C.; Thomas, R. J.; Fox, J. L.;
Winter, B.
2005AdSpR..36.1422H Altcode:
Our current ways of observing the Sun with spectrometers and imagers
are limited. With a slit spectrometer, we require time to build up a
2-D image which results in temporal blurring. When we use a traditional
imager, we have no ability to measure and detect line-of-sight flows
or to discriminate contributions from gas at different temperatures
in the imager passband, causing spectral confusion of the images. For
Solar Orbiter, the combination of an exciting new viewpoint of the
Sun, and the best resolution of the corona ever seen, means that we
require the best time cadence and velocity information that we can
get. The spatial resolution expected from the imager on Solar Orbiter
will reach approximately 70 km. At such a resolution in the corona,
we expect to see the fundamental magnetic flux tubes, which are
predicted to have high velocities. This is also the scale at which we
will be able to search for evidence basic physical processes such as
magnetic reconnection. We will describe the design of an imager that
gives not only high quality images, but also provides simultaneous
information about plasma flows and temperature. A prototype instrument
is being flown on a NASA sounding rocket next year. The concept will
be described, along with some methods of extracting the spectroscopic
information.
---------------------------------------------------------
Title: The Solar-B EUV imaging spectrometer and its science goals
Authors: Culhane, J. L.; Harra, L. K.; Doschek, G. A.; Mariska, J. T.;
Watanabe, T.; Hara, H.
2005AdSpR..36.1494C Altcode:
The Solar-B mission includes an Extreme-UV Imaging Spectrometer
(EIS). It detects photons in the ranges 170-210 and 250-290 Å which
include emission lines from several highly ionised species that exist
at temperatures log T = 4.7, 5.6, 5.8, 5.9 and 6.0-7.3 K. In this
paper, we will describe the design and operation of the instrument
and present its performance parameters, e.g., spectral and spatial
resolution and sensitivity. Preliminary results of recent calibration
measurements will be described. Its role in the Solar-B mission will
be illustrated with reference to several key science topics that the
EIS is expected to address. The anticipated observing strategy for
the first three months of the mission will be outlined.
---------------------------------------------------------
Title: The Relationship between Prominence Eruptions and Global
Coronal Waves
Authors: Attrill, G. D. R.; Harra, L. K.; Matthews, S. A.; Foley,
C. R.; Sterling, A. C.
2004ASPC..325..409A Altcode:
There has been much debate over the physical mechanism for producing
global coronal waves (`EIT waves'). In this work, we investigate
whether filament eruptions are directly associated with coronal
waves. We analyse 45 coronal waves and search for evidence of
filament eruptions. We used SOHO-EIT data, and EIT data along with
any available ground-based Hα data to search for filament eruptions,
and found that more than 50 % of coronal waves are clearly associated
with eruptions. The speeds of the coronal waves, and the filament
eruptions are similar. We discuss the implications of these results.
---------------------------------------------------------
Title: Effect of solar energetic particle (SEP) events on the
radiation exposure levels to aircraft passengers and crew: Case
study of 14 July 2000 SEP event
Authors: Iles, R. H. A.; Jones, J. B. L.; Taylor, G. C.; Blake, J. B.;
Bentley, R. D.; Hunter, R.; Harra, L. K.; Coates, A. J.
2004JGRA..10911103I Altcode:
We investigate the circumstances required for aircrew and passengers
to experience an increased radiation exposure rate from a solar
energetic particle (SEP) event occurring during a flight. The effects
of the 14 July 2000 National Oceanic and Atmospheric Administration
S3 class SEP event are examined using ground-based and satellite
measurements together with coincident measurements made using a tissue
equivalent proportional counter (TEPC) on board a Virgin Atlantic
Airways flight from London Heathrow to Hong Kong. In this paper we
present the first measurements made during a SEP event using a TEPC at
flight altitudes. Our results indicate that there were no increased
radiation levels detected during the flight due to the SEPs, but the
measurements agreed well with the CARI-6 model calculations made using
a heliocentric potential value derived immediately prior to the SEP
event. In addition, a prolonged increase in the >85 MeV particle
flux is observed for up to 2 days after the SEP onset by the SAMPEX
spacecraft at latitudes >55°.
---------------------------------------------------------
Title: What causes solar active region loops to exist at transition
region temperatures?
Authors: Harra, Louise K.; Mandrini, Cristine H.; Matthews, Sarah A.
2004SoPh..223...57H Altcode:
High-lying, dynamic loops have been observed at transition region
temperatures since Skylab observations. The nature of these loops has
been debated for many years with several explanations having been
put forward. These include that the loops are merely cooling from
hotter coronal loops, that they are produced from siphon flows, or
that they are loops heated only to transition region temperatures. In
this paper we will make use of combined SOHO-MDI (Michelson-Doppler
Imager), SOHO-CDS (Coronal Diagnostic Spectrometer) and Yohkoh SXT
(Soft X-ray Telescope) datasets in order to determine whether the
appearance of transition region loops is related to small-scale
flaring in the corona, and to estimate the magnetic configuration of
the loops. The latter allows us to determine the direction of plasma
flows in the transition region loops. We find that the appearance of
the transition region loops is often related to small-scale flaring
in the corona and in this case the transition region loops appear to
be cooling with material draining down from the loop top.
---------------------------------------------------------
Title: Relating magnetic field strengths to hard X-ray emission in
solar flares
Authors: Goff, C. P.; Matthews, S. A.; van Driel-Gesztelyi, L.; Harra,
L. K.
2004A&A...423..363G Altcode:
The observation of hard X-ray (HXR) emission in solar flares provides
important diagnostic information about the acceleration and subsequent
transport of energetic electrons in the flare process. However,
while hard X-rays are thought to be emitted from the flare footpoints
through thick-target bremsstrahlung interactions, the details of the
transport of accelerated electrons through the solar atmosphere still
remains unclear. <P />Trapping of the electrons is one particular
effect that is expected to occur as a result of the convergence of the
magnetic field between the corona and the chromosphere. In this case
the brightness of the HXR footpoints should be related to the strength
of the magnetic field present and we would expect greater precipitation
and higher HXR intensities at the footpoints with lower magnetic field
strength. This relationship has been observed to hold in many flares
(see \citealt{Sakaothesis}) but interestingly the opposite relationship,
where the stronger HXR source is found at the stronger magnetic field
region, has also been observed in an event studied by \citet{Asai}. <P
/>Using Data from Yohkoh's Hard X-Ray Telescope (HXT) and SOHO's
Michelson Doppler Imager (MDI) we have studied the magnetic field
strengths at the footpoints of a sample of 32 flares and have compared
them to the hard X-ray brightness to determine whether the expected
ratios are seen. We find that contrary to the expected relationship
the brighter HXR footpoint is found in the region of stronger magnetic
field in approximately one third of our sample of events. We discuss
the implications of these results in terms of the transport mechanisms.
---------------------------------------------------------
Title: Improved data for solar flare X-ray spectral analysis
Authors: Phillips, K. J. H.; Rainnie, J. A.; Harra, L. K.; Dubau,
J.; Keenan, F. P.; Peacock, N. J.
2004A&A...416..765P Altcode:
The inclusion of collisional rates for He-like Fe and Ca ions
is discussed with reference to the analysis of solar flare Fe
XXV and Ca XIX line emission, particularly from the Yohkoh Bragg
Crystal Spectrometer (BCS). The new data are a slight improvement
on calculations presently used in the BCS analysis software in that
the discrepancy in the Fe XXV y and z line intensities (observed
larger than predicted) is reduced. Values of electron temperature from
satellite-to-resonance line ratios are slightly reduced (by up to 1 MK)
for a given observed ratio. The new atomic data will be incorporated
in the Yohkoh BCS databases. The data should also be of interest for
the analysis of high-resolution, non-solar spectra expected from the
Constellation-X and Astro-E space missions. A comparison is made of a
tokamak S XV spectrum with a synthetic spectrum using atomic data in the
existing software and the agreement is found to be good, so validating
these data for particularly high-n satellite wavelengths close to the
S XV resonance line. An error in a data file used for analyzing BCS
Fe XXVI spectra is corrected, so permitting analysis of these spectra.
---------------------------------------------------------
Title: An Observational Test for Coronal Heating Models
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.;
Harra, L. K.; Klimchuk, J. A.
2004IAUS..219..473V Altcode: 2003IAUS..219E..97V
We correlate the evolution of the mean X-ray flux emission measure
and temperature (Yohkoh SXT & BCS) with the magnetic flux density
(SOHO/MDI) in active region NOAA 7978 from its birth throughout its
decay for five solar rotations. We show that these plasma parameters
together with other quantities deduced from them such as the density
and the pressure follow power-law relationships with the mean magnetic
flux density (bar{B}). We derive the dependence of the mean coronal
heating rate on the magnetic flux density. We use the obtained scaling
laws of coronal loops in thermal equilibrium to derive observational
estimates of the scaling of the coronal heating with bar{B}. These
results are used to test the validity of coronal heating models. We
find that models invoking stochastic buildup of energy current layers
and MHD turbulence are in best agreement with the observations. This
narrows down the range of possible models retained by previous results
obtained for individual coronal loops as well as for the global coronal
emission of the Sun and cool stars.
---------------------------------------------------------
Title: On the origin of loops with transition region temperatures
Authors: Mandrini, C. H.; Harra, L. K.; Matthews, S. A.
2004BAAA...47...32M Altcode:
Very dynamic loops at transition region temperatures have been observed
at coronal heights since more than 30 years. The origin of these loops
is still debated and several explanations have been put forward. It
has been proposed that the loops are merely cooling from hotter coronal
loops, that they are produced from siphon flows, or that they are loops
heated only to transition region temperatures. In this work we combine
SOHO/MDI (Michelson-Doppler Imager), SOHO/CDS (Coronal Diagnostic
Spectrometer) and Yohkoh/SXT (Soft X-ray Telescope) observations to
determine whether the appearance of transition region loops is related
to small-scale flaring in the corona, and to compute the magnetic
configuration of the loops. The latter allows us to determine the
direction of plasma flows in the loops. In our analyzed examples the
appearance of the transition region loops is often related to small
flares and, consequently, the plasma flows from the loop top to the
footpoints as it cools down.
---------------------------------------------------------
Title: The Physics of the Sun
Authors: Harra, Louise
2004spsc.book..187H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal emission from the active binary CC Eri
Authors: Kay, H.; Matthews, S.; Harra, L.; Culhane, L.
2004cosp...35.1742K Altcode: 2004cosp.meet.1742K
The binary star CC Eri (HD 16157) is an active star with a short
orbital period of 1.56 days. It was observed for more than 35 ks with
XMM-Newton in September 2003, during which it flared several times
and showed a high level of X-ray variability. Preliminary analysis of
the thermal structure and elemental abundances of the corona of CC Eri
will be presented, along with an investigation into variation in the
coronal density and opacity during flares. Simultaneous observations
with the Optical Monitor, used to make a comparison between UV and
X-ray emission during the flares, will also be presented.
---------------------------------------------------------
Title: An imager with added value for the Solar Orbiter mission
Authors: Harra, L.; Kankelborg, C.; Thomas, R.; Fox, J.; Winter, B.
2004cosp...35.1120H Altcode: 2004cosp.meet.1120H
Our current ways of observing the Sun with spectrometers and imagers
are limited. When we use a spectrometer, we require time to build
up an image. When we use a traditional imager we have no ability to
measure and detect Doppler flows. These limitations will become even
more restrictive on Solar Orbiter. The combination of an exciting new
viewpoint of the Sun, and the best resolution of the corona ever seen,
means that we require the best time cadence and velocity information
that we can get. The spatial resolution expected from the imager on
Solar Orbiter will reach approximately 30 km. At such a resolution in
the corona, we expect to see the fundamental flux tubes, which are
predicted to have high velocities. This is also the scale at which
we will be able to observe basic physical processes such as magnetic
reconnection occurring. We will describe a design of an imager that
allows not only high quality images, but also obtains information about
Doppler flows simultaneously. A prototype instrument is being flown
on a NASA sounding rocket this year. The concept will be described,
along with some methods of deconvolving the spectroscopic information.
---------------------------------------------------------
Title: Space Science
Authors: Harra, Louise K.; Mason, Keith O.
2004spsc.book.....H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Using Quantum Physics and Spectroscopy to Probe the Physical
Universe
Authors: Harra, Louise; Mason, Keith
2004spsc.book..251H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic observations of coronal waves and coronal
mass ejections
Authors: Harra, L.
2004cosp...35.4417H Altcode: 2004cosp.meet.4417H
I will review current spectroscopic observations of large-scale dynamic
phenomena such as global coronal waves and coronal mass ejections. The
aim is to determine plasma parameters such as flows. temperatures and
densities to obtain a physical understanding of these phenomena.
---------------------------------------------------------
Title: Introduction
Authors: Harra, Louise; Mason, Keith
2004spsc.book....1H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar 'EIT Waves' - What are They?
Authors: Harra, L. K.; Sterling, A. C.
2004IAUS..219..498H Altcode: 2003IAUS..219E..65H
Using spectral data from the Coronal Diagnostic Spectrometer (CDS)
instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft
we observe a coronal wave feature which occurred in association with a
solar eruption and flare on 1998 June~13. EUV images from the Transition
Region and Coronal Explorer (TRACE) satellite show that the coronal
wave consists of two aspects: (1) a “bright wave” which shows up
prominently in the TRACE difference images moves with a velocity of
approximately 200km/s and is followed by a strong dimming region behind
it and (2) a “weak wave” which is faint in the TRACE images has a
velocity of about 500km/s and appears to disperse out of the bright
wave. A “high-velocity” CDS feature however occurs after the weak wave
passes which appears to correspond to ejection of cool filament-like
material in TRACE images. Our observations have similarities with a
numerical simulation model of coronal waves presented by Chen etal
(2002) who suggests that coronal waves consist of a faster-propagating
piston-driven portion and a more slowly-propagating portion due to
the opening of field lines associated with an erupting filament.
---------------------------------------------------------
Title: Evidence of Flaring in a Transequatorial Loop on the Sun
Authors: Harra, Louise K.; Matthews, Sarah A.; van Driel-Gesztelyi,
Lidia
2003ApJ...598L..59H Altcode:
We present evidence of flaring behavior in a transequatorial loop (TEL)
that lights up in soft X-rays on 2000 July 13. The large loop structure
connects NOAA Active Regions 9070/9066 in the northern hemisphere and
AR 9069/9068 in the southern hemisphere. We follow the loop systems for
2 days and observe several pieces of evidence strongly suggesting flare
behavior of the form seen in standard flaring in active regions. These
include brightenings of the loop structure, cooling of plasma that is
seen both in soft X-rays and in the transition region temperatures,
morphological evidence of reconnection inflow, and blueshifts around
the footpoint of the TEL suggestive of chromospheric evaporation. We
present, to our knowledge for the first time, observations of TEL in
the O V emission line.
---------------------------------------------------------
Title: A study of the unification of quiet-Sun transient-event
phenomena
Authors: Harrison, R. A.; Harra, L. K.; Brković, A.; Parnell, C. E.
2003A&A...409..755H Altcode:
A number of small-scale, globally distributed solar transient
event-types have been reported in the literature. Their potential
role in fundamental processes in the solar atmosphere, such as coronal
heating and wind acceleration, is under active investigation. However,
the event-types, such as those known as blinkers, explosive events,
EUV (extreme-UV) network and cell brightenings, network flares, heating
events, nanoflares and EUV brightenings are basically classifications
which are driven to a large extent by different observational techniques
and different instruments rather than the identification of a clear
differing physical phenomenon. We investigate the different instrumental
and technique limitations and attempt to identify any unification
of the reported quiet-Sun transient, small-scale phenomena. We find
that once observational techniques have been considered, a number of
the different classifications appear to be the same. This suggests
that events known as blinkers, network and cell brightenings and EUV
brightenings are the same event-type. We suggest that the term blinker
be used as a generic term to describe these events. However, there
appears to be little evidence that blinkers and explosive events are
directly related. Furthermore, although a small percentage of blinkers
and nanoflares/heating events appear to be related to one another,
these events pose a number of important questions suggesting that either
(i) blinkers and nanoflare/heating events are all created by the same
mechanism, i.e. for some blinker events, the conditions are such that
higher temperatures are found, or (ii) there are two types of event,
including the “traditional” blinker which is effectively a transition
region brightening driven by a density or filling factor enhancement,
and a mini-flare-like event which reaches higher temperatures,
presumably driven by reconnection.
---------------------------------------------------------
Title: Preface
Authors: Harra, L. K.
2003AdSpR..32..883H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flare characteristics: Properties of eruptive and non-eruptive
events and their associations
Authors: Kay, H. R. M.; Culhane, J. L.; Harra, L. K.; Matthews, S. A.
2003AdSpR..32.1051K Altcode:
The complex: relationship between solar flares and coronal mass
ejections is investigated using a comparison of flare parameters for
a total of 69 ejective and non-ejective flares. In the case of solar
flares which do not show mass ejection there seems to be a clear
relationship between the peak intensity and duration, with higher
intensity events being of longer duration. Systematic differences in
the relationship between peak temperature and intensity for the two
types of events are also evident, with flares accompanied by CMEs
tending to have lower peak temperatures than non-ejective events of
the same intensity. Whilst there appears to be a clear relationship
between the length of rise and decay phase in a flare, there are
no systematic differences in the parameters between ejective and
non-ejective flares. A total of eleven EIT waves were found, all of
which were associated with CMEs. There is no apparent correlation
between the occurrence of an EIT wave and the peak intensity or rise
time of the associated flare.
---------------------------------------------------------
Title: UV spectroscopy with SOHO
Authors: Harra, L. K.; Brekke, P.
2003AdSpR..32..965H Altcode:
The UV spectroscopy from SOHO has provided new and exciting results
from a wide range of phenomena observed on the Sun. Determination of
plasma parameters such as velocity, density, temperatures, line widths
and abundances have provided new physical insight into fundamental
problems in solar physics. These include magnetic reconnection, quiet
Sun coronal heating, active region dynamics, flows in solar flares,
formation of the solar wind, determination of coronal mass ejection
onset, characteristics of coronal waves and the twisting of magnetic
structures. This paper will review these results and discuss what can
be achieved with future spectroscopic instrumentation.
---------------------------------------------------------
Title: A search for X-ray variability in the open cluster NGC 2516
Authors: Ramsay, Gavin; Harra, Louise; Kay, Hilary
2003MNRAS.341.1388R Altcode: 2003astro.ph..2200R
We present the results of a search for X-ray variability in the
Galactic open cluster NGC 2516. This cluster has been observed on
eight occasions using XMM-Newton, making it an excellent target for
such a study. We find four sources that show significant variability,
implying the detection of one significantly variable source every 25
ks. All sources exhibit spectra that can be fitted using an absorbed
one- or two-temperature thermal plasma model. The brightest of these
flares also show a prominent iron line near ~7.0 keV. All four sources
lie near the observed main sequence of NGC 2516, suggesting that they
are cluster members. We propose that at least three of the four objects
are RS CVn systems. We compare the properties of the brightest flare
with those of solar flares.
---------------------------------------------------------
Title: Imaging and Spectroscopic Investigations of a Solar Coronal
Wave: Properties of the Wave Front and Associated Erupting Material
Authors: Harra, Louise K.; Sterling, Alphonse C.
2003ApJ...587..429H Altcode:
Using spectral data from the Coronal Diagnostic Spectrometer (CDS)
instrument on the Solar and Heliospheric Observatory spacecraft, we
observe a coronal wave feature (often referred to as an EIT wave) that
occurred in association with a solar eruption and flare on 1998 June
13. EUV images from the Transition Region and Coronal Explorer (TRACE)
satellite show that the coronal wave consists of two aspects: (1) a
“bright wave,” which shows up prominently in the TRACE difference
images, moves with a velocity of approximately 200 km s<SUP>-1</SUP>,
and is followed by a strong dimming region behind it and (2) a “weak
wave,” which is faint in the TRACE images, has a velocity of about 500
km s<SUP>-1</SUP>, and appears to disperse out of the bright wave. The
weak wave passes through the CDS field of view but shows little or
no line-of-sight motions in CDS spectra (velocities less than about
10 km s<SUP>-1</SUP>). Only a small portion of the bright wave passes
the CDS field of view, with the spectral lines showing insignificant
shifts. A high-velocity CDS feature, however, occurs after the weak wave
passes, which appears to correspond to ejection of cool, filament-like
material in TRACE images. Our observations have similarities with
a numerical simulation model of coronal waves presented by Chen et
al., who suggest that coronal waves consist of a faster propagating,
piston-driven portion and a more slowly propagating portion due to
the opening of field lines associated with an erupting filament.
---------------------------------------------------------
Title: The association of transequatorial loops in the solar corona
with coronal mass ejection onset
Authors: Glover, A.; Harra, L. K.; Matthews, S. A.; Foley, C. A.
2003A&A...400..759G Altcode:
It has been shown that transequatorial loops can disappear in
association with the onset of a coronal mass ejection (CME) (Khan
& Hudson \cite{khan}). We extend this result by considering a
larger sample of transequatorial loop systems (TLS) to investigate
their associated flaring and CME activity. We find 10 of a total
18 TLS considered here to be associated with flaring and CME onset
originating from a connected active region. A total 33 cases of
flaring and associated CME onset are observed from these 10 systems
during their lifetime. We observe the influence of this activity on
the TLS in each case. In contrast to the Khan & Hudson result,
we find evidence that transequatorial loop eruption leading to soft
X-ray brightening equivalent in temperature to a B-class flare is
equally as common as dimming in the corona. Consequently we conclude
that the scenario observed by Khan & Hudson is not universal and
that other types of CME-TLS association occur. It was found that for
transequatorial loops that were associated with CMEs the asymmetry in
longitude was larger than for those that were not associated to a CME
by 10<SUP>o</SUP>. In addition, the extent in latitude (as a measure
of the loop length) was nearly twice as large for those TLS associated
with CMEs than those that were not. The asymmetry in latitude was
actually on average larger for those TLS not associated with CMEs,
than for those that were. This suggests that differential rotation is
not a major contributor to the production of CMEs from transequatorial
loops. Instead it is more likely for a CME to be produced if the loop is
long, and if there is a large asymmetry in longitude. The implications
of these results for CME onset prediction are discussed.
---------------------------------------------------------
Title: The Long-Term Evolution of AR 7978: The Scalings of the
Coronal Plasma Parameters with the Mean Photospheric Magnetic Field
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.;
Harra, L.; Klimchuk, J. A.
2003ApJ...586..579V Altcode:
We analyze the evolution of the fluxes observed in X-rays and correlate
them with the magnetic flux density in active region (AR) NOAA 7978
from its birth throughout its decay, for five solar rotations. We
use Solar and Heliospheric Observatory Michelson Doppler Imager
(MDI) data, together with Yohkoh Soft X-Ray Telescope (SXT) and
Yohkoh Bragg Crystal Spectrometer (BCS) data, to determine the global
evolution of the temperature and the emission measure of the coronal
plasma at times when no significant brightenings were observed. We
show that the mean X-ray flux and derived parameters, temperature
and emission measure (together with other quantities deduced from
them, such as the density and the pressure), of the plasma in the AR
follow power-law relationships with the mean magnetic flux density
(B). The exponents (b) of these power-law functions (aB<SUP>b</SUP>)
are derived using two different statistical methods, a classical
least-squares method in log-log plots and a nonparametric method,
which takes into account the fact that errors in the data may not be
normally distributed. Both methods give similar exponents, within
error bars, for the mean temperature and for both instruments (SXT
and BCS); in particular, b stays in the range [0.27, 0.31] and [0.24,
0.57] for full-resolution SXT images and BCS data, respectively. For
the emission measure, the exponent b lies in the range [0.85, 1.35]
and [0.45, 1.96] for SXT and BCS, respectively. The determination of
such power-law relations, when combined with the results from coronal
heating models, can provide us with powerful tools for determining the
mechanism responsible for the existence of the high-temperature corona.
---------------------------------------------------------
Title: The Long-Term Evolution of AR 7978: Testing Coronal Heating
Models
Authors: Démoulin, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.;
Klimchuk, J. A.; Harra, L.
2003ApJ...586..592D Altcode:
We derive the dependence of the mean coronal heating rate on the
magnetic flux density. Our results are based on a previous study of
the plasma parameters and the magnetic flux density (B) in the active
region NOAA 7978 from its birth to its decay, throughout five solar
rotations using the Solar and Heliospheric Observatory Michelson
Doppler Imager, Yohkoh Soft X-Ray Telescope (SXT), and Yohkoh Bragg
Crystal Spectrometer (BCS). We use the scaling laws of coronal loops
in thermal equilibrium to derive four observational estimates of the
scaling of the coronal heating with B (two from SXT and two from
BCS observations). These results are used to test the validity of
coronal heating models. We find that models based on the dissipation
of stressed, current-carrying magnetic fields are in better agreement
with the observations than models that attribute coronal heating to
the dissipation of MHD waves injected at the base of the corona. This
confirms, with smaller error bars, previous results obtained for
individual coronal loops, as well as for the global coronal emission
of the Sun and cool stars. Taking into account that the photospheric
field is concentrated in thin magnetic flux tubes, both SXT and BCS
data are in best agreement with models invoking a stochastic buildup
of energy, current layers, and MHD turbulence.
---------------------------------------------------------
Title: The soft X-ray characteristics of solar flares, both with
and without associated CMEs
Authors: Kay, H. R. M.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.;
Green, L. M.
2003A&A...400..779K Altcode:
The complex relationship between solar flares and coronal mass ejections
is investigated using a comparison of flare parameters for a total
of 69 ejective and non-ejective flares. In the case of solar flares
which do not show mass ejection there seems to be a clear relationship
between the peak intensity and duration, with higher intensity events
being of longer duration. Systematic differences in the relationship
between peak temperature and intensity for the two types of event are
also evident, with flares associated with CMEs tending to have lower
peak temperatures than non-ejective events of the same intensity. Whilst
there appears to be a clear relationship between the length of rise and
decay phase in a flare, there are no systematic differences in these
parameters for ejective and non-ejective flares. A total of eleven
“EIT waves” were found, all of which were associated with CMEs. There
is no apparent correlation between the occurrence of an EIT wave and
the peak temperature, intensity or rise time of the associated flare.
---------------------------------------------------------
Title: Evidence for a Flux Rope driven EUV wave and CME: Comparison
with the Piston Shock Model
Authors: Foley, C. R.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.;
Kitai, R.
2003A&A...399..749F Altcode:
This paper examines the relationship between a coronal wave, filament
eruption, flare and Coronal Mass Ejection (CME) which occurred on
2001, April 10th. We study the pre-flare activity which includes the
eruption of a filament and a coronal wave. A large X-ray flare and
a CME follow. We discuss how these phenomena are related and compare
our results to recent models. These are found to be largely consistent
with the numerical simulations of a flux rope driven CME as presented
recently in Chen et al. (2002).
---------------------------------------------------------
Title: The occurrence of single hard x-ray sources in solar flares
Authors: Goff, C. P.; Matthews, S. A.; Harra, L. K.
2003AdSpR..32.2483G Altcode:
The 'standard' thick target flare model predicts the existence of strong
hard X-ray emission at the footpointsof a flare loop. However, Yohkoh
observations suggest that up to 20% of events with data available in
three or more Hard X-ray Telescope (HXT) channels show only a single
source. Combining datasets from Yohkoh, the Solar and Heliospheric
Observatory (SOHO), and Nobeyama Radio Heliograph (NoRH), we compare
the characteristics of these single source events to double source
events. The objective of this study is to determine whether these
represent unresolved double footpoints, asymmetric electron deposition
due to magnetic mirroring effects, or a genuine departure from the
'standard' model.
---------------------------------------------------------
Title: How to test coronal heating models?
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
Klimchuk, J. A.; Harra, L. K.
2003BAAA...46....5M Altcode:
We have tested coronal heating models following two different
approaches. In the first case, we compared the dependence of the
coronal heating rate predicted by theoretical models with the
observed one, deriving the scalings of parameters, such as: the
density, temperature and intensity of the coronal magnetic field,
with the length of magnetic field lines. To do so, we combined density
and temperature measurements for 47 coronal loops with magnetic field
models for 14 active regions. In the second case, we analyzed the long
term evolution of an active region observed during seven rotations
on the solar disk and we determined the dependence of the observed
heating rate with the magnetic field density (bar{B}), after finding
the scalings of plasma parameters with bar{B}. In both cases, we found
that models based on the dissipation of stressed, current-carrying
magnetic fields (called direct current models) are in better agreement
with observations than models that attribute coronal heating to the
dissipation of MHD waves injected at the base of the corona (called
alternate current models). Taking into account that the photospheric
field is concentrated in thin magnetic flux tubes, observations are
in best agreement with models invoking a stochastic buildup of energy,
current layers and MHD turbulence, within direct current models.
---------------------------------------------------------
Title: Multi-wavelength observations of the pre-cursor phase of
solar flares
Authors: Matthews, S. A.; Harra, L. K.; Culhane, J. L.
2003AdSpR..32.2553M Altcode:
Observational studies of the pre-cursor phase of solar flares have
shown that there are many and varied signatures that may or may not
indicate the probable onset of a flare. Combining data from Yohkoh,
SOHO and TRACE and more recent observations from RHESSI, SOHO and TRACE
we, investigate the relationships between the different manifestations
of pre-flare behaviour in two solar flares with a view to determining
how they are related to the subsequent flare energy release. We find
that in one case the preflare activity seems strongly related to the
subsequent flare and probably represents a build-up of energy in the
active region prior to flare onset. The second case we find to be less
clear cut suggesting that significant further work remains to be done
in order to determine which pre-flare signatures are most useful in
indicating the build-up to flare onset.
---------------------------------------------------------
Title: The Solar Corona as Seen by Yohkoh
Authors: Harra, L. K.
2002ASPC..277..277H Altcode: 2002sccx.conf..277H
No abstract at ADS
---------------------------------------------------------
Title: The Coronal Emission of Photospheric Magnetic Fragments
Authors: McDonald, L.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.
2002SoPh..211..125M Altcode:
This paper examines the relationship between magnetic dipoles in the
photosphere and X-ray bright points (XBPs) in the corona, using an XBP
special campaign dataset obtained by the Yohkoh SXT and the NSO/Kitt
Peak magnetograph. We find that for the cases where a simple dipole
exists in the photosphere, the condition that they are separated by a
distance less than the interaction distance defined by Longcope1998 is
favorable for an XBP to be observed. For the cases where the magnetic
topology is more complicated due to the addition of an extra fragment,
we find that the geometry of the magnetic fragments is a major factor
that determines if an XBP is observed. XBPs are more likely to be formed
above magnetic fragments arranged in such a way that photospheric
motions giving rise to reconnection between any two fragments will
also give rise to reconnection with the remaining fragment.
---------------------------------------------------------
Title: Explosive events on the Sun
Authors: Harra, Louise K.
2002RSPTA.360.2757H Altcode:
I describe two of the most dynamic and highly energetic phenomena in the
Solar System-the explosive flares that can occur when plasma is confined
by magnetic fields and the large-scale ejections of material known as
'coronal mass ejections'. These explosive events are poorly understood
and yet occur in a variety of contexts in the Universe, ranging from
planetary magnetospheres to active galactic nuclei. Understanding why
flares and coronal mass ejections occur is a major goal across a wide
range of space physics and astrophysics. Although explosive events from
the Sun have dramatic effects on Earth, flares in other stars, for
example, can be vastly more energetic and have an even more profound
effect on their environment. We are now in the unprecedented position
of having access to a number of space observatories dedicated to the
Sun: the Yohkoh spacecraft, the Solar and Heliospheric Observatory,
the Transition Region and Coronal Explorer and the Ramaty High Energy
Solar Spectroscopic Imager. These cover a wide wavelength range from
white light to gamma rays with both spectroscopy and imaging, and
allow huge progress to be made in understanding the processes involved
in such large explosions. The high-resolution data show dramatic and
complex explosions of material on all spatial scales on the Sun. They
have revealed that the Sun is constantly changing everywhere on its
surface-something that was never imagined before. One of the mechanisms
that has been proposed to account for the large energy release is
magnetic reconnection. Recent observations from space increasingly
support this view. This article will discuss those observations
that support this model and also those that suggest different
processes. The current space missions have given us an excellent
insight into the actual explosive processes in the Sun. However,
they have provided us with only a tantalizing glimpse of what causes
the elusive trigger. Future missions such as Solar-B (the follow-on to
Yohkoh), the Solar Terrestrial Relations Observatory, the Solar Dynamics
Observatory and the Solar Orbiter mission will allow us to probe the
trigger in a way that was not dreamt of a decade ago, by providing
stereo views, measurements from Sun-grazing orbit, and much higher
spatial, temporal and spectral resolution. It is an exciting time for
solar physics and everything that we learn about the Sun will improve
our ability to understand other magnetic phenomena in the Universe.
---------------------------------------------------------
Title: The Relationship between Duration and Intensity for Ejective
and Non-Ejective Solar and Stellar Flares
Authors: Magee, H. R. M.; Harra, L. K.; Matthews, S. A.
2002ASPC..277..533M Altcode: 2002sccx.conf..533M
No abstract at ADS
---------------------------------------------------------
Title: Doppler Detection of Material Outflows from Coronal Intensity
“Dimming Regions” During Coronal Mass Ejection Onset
Authors: Sterling, A.; Harra, Louise
2002AAS...200.3709S Altcode: 2002BAAS...34..696S
“Coronal dimmings,” localized regions showing a precipitous drop in
EUV or X-ray emission, are a key coronal signature of the sources of
Coronal Mass Ejections (CMEs). Researchers often assume that dimmings
result from a depletion of coronal material (i.e., a decrease in density
along the line-of-sight), even when no obvious moving structure can be
detected in images. Yet, this explanation has not been unambiguously
established; in principle the dimmings could, for example, be due
to a dramatic change in the temperature of the emitting material
instead. Here we present the most direct evidence to-date that the
dimmings result from mass loss, by observing Doppler motions of material
leaving the regions as they dim. Using spectral data from the Coronal
Diagnostic Spectrometer (CDS) on SOHO, we observe Doppler shifts in
two different events. One of these, from 1998 March 31 near 9 UT,
was near the solar limb and was associated with a CME traveling in the
plane of the sky, while the other event, from 1999 July 19 near 1:50
UT, was on the solar disk and was associated with an Earth-directed
“halo” CME\@. The limb event shows Doppler signatures of ≈ 30 km
s<SUP>-1</SUP> in coronal (Fe xvi and Mg ix) emission lines, where the
enhanced velocities coincide with the locations of coronal dimming. An
“EIT wave” accompanies the disk event, and a dimming region behind
the wave shows strong blue-shifted Doppler signatures of ≈ 100 km
s<SUP>-1</SUP> in the O v transition region line. These results provide
strong evidence that material from the dimming regions feeds into
the CMEs. This work was supported by NASA's SR&T and GI Programs,
and by PPARC.
---------------------------------------------------------
Title: Changes in the solar magnetic field preceding a coronal
mass ejection
Authors: Harra, L. K.
2002JASTP..64..505H Altcode: 2002JATP...64..505H
The combined observing power of the Yohkoh, SOHO and TRACE spacecraft,
along with the continuing ground-based observations has proved
invaluable for the detection of changes in the magnetic morphology
preceding coronal mass ejections (CMEs). A wide range of activity
from small scale dimmings to large scale eruptions covering half
the solar disk have been observed. The relationship between flares
and CMEs has also become clearer. Rather than one event causing the
other it would seem that it is a global change in the magnetic field
which causes both. Recently, there has been a lot of interest in the
sigmoid (S-shaped) structures seen in soft X-rays. The likelihood of
a CME occurring appears to increase if there is a sigmoidal structure
observed. This has formed the basis of more extensive studies into
predicting the time and location of a CME from the changes in behaviour
of features on the solar disk.
---------------------------------------------------------
Title: The magnetic topology of a sigmoid
Authors: Glover, Alexi; Ranns, Neale D. R.; Brown, Daniel S.; Harra,
Louise K.; Matthews, Sarah A.; Culhane, J. Leonard
2002JASTP..64..497G Altcode: 2002JATP...64..497G
Recent surveys of solar features have linked the “sigmoid-to-arcade”
scenario observed in the soft X-ray corona to coronal mass ejection
(CME) onset (Geophys. Res. Lett. 26 (1999) 627, Geophys. Res. Lett. 14
(1998) 2481). Further to these observations, incorporation of
extreme-ultraviolet, white light and H-alpha data into such a survey
(Geophys. Res. Lett. 27 (2000) 2161) has illustrated the need
for a quantitative definition of the term “sigmoid” and further
understanding of such features if they are to be used as a means by
which to predict CME onset. We analyse two sample active regions in
detail, each appearing both sigmoidal and eruptive in Yohkoh soft
X-ray telescope (SXT) full-disk data. Both regions were observed
during October 1997 and each produced a flare displaying eruptive
characteristics. In each case, formation of a flare-arcade was
observed by both SXT and the extreme ultraviolet imaging telescope
(EIT) following the event. EUV dimming and coronal EIT waves were also
observed in each case. We have studied each active region both before
and after eruption using soft X-ray, EUV and H-alpha data. A linear
force-free field extrapolation has also been applied as a means by
which to determine the active region field deviation from potential
in each case. Each active region was observed to erupt by means of a
different mechanism and while both events show signatures of eruption
and consequently, mass ejection, only one produced a CME large enough
to be observed by the SoHO large angle spectroscopic coronagraph. The
implications of these observations in terms of CME prediction are
discussed.
---------------------------------------------------------
Title: Multi-wavelength observations of an X-class flare without a
coronal mass ejection.
Authors: Green, L. M.; Matthews, S. A.; van Driel-Gesztelyi, L.;
Harra, L. K.; Culhane, J. L.
2002SoPh..205..325G Altcode:
Developments in our knowledge of coronal mass ejections (CMEs) have
shown that many of these transients occur in association with solar
flares. On the occasions when there is a common occurrence of the
eruption and the flare, it is most likely that the flare is of high
intensity and/or long-duration (Burkepile, Hundhausen, and Webb,
1994; Munro et al., 1979; Webb and Hundhausen, 1987). A model for
the relationship between the long-duration event and eruption has
been developed (Carmichael, 1964; Sturrock, 1966; Hirayama, 1974;
Kopp and Pneuman, 1976), but not so for the high-intensity flares and
eruptions. This work investigates the magnetic topology changes that
occur for a X1.2 GOES classification flare which has no associated
CME. It is found that the flare is likely to result from the interaction
between two pre-existing loops low in the corona, producing a confined
flare. Slightly higher in the corona, a loop is observed which
exhibits an outward motion as a result of the reconfiguration during
reconnection. The objective of this work is to gain insight on the
magnetic topology of the event which is critical in order to determine
whether a high-intensity flare is likely to be related to a CME or not.
---------------------------------------------------------
Title: AstroGrid: the UK's Virtual Observatory Initiative
Authors: Mann, Robert G.; Astrogrid Consortium; Lawrence, Andy;
Davenhall, Clive; Mann, Bob; McMahon, Richard; Irwin, Mike; Walton,
Nic; Rixon, Guy; Watson, Mike; Osborne, Julian; Page, Clive; Allan,
Peter; Giaretta, David; Perry, Chris; Pike, Dave; Sherman, John;
Murtagh, Fionn; Harra, Louise; Bentley, Bob; Mason, Keith; Garrington,
Simon
2002ASPC..281....3M Altcode: 2002adass..11....3M
AstroGrid is the UK's Virtual Observatory (VO) initiative. It brings
together the principal astronomical data centres in the UK, and has
been funded to the tune of ∼pounds 5M over the next three years,
via PPARC, as part of the UK e--science programme. Its twin goals
are the provision of the infrastructure and tools for the federation
and exploitation of large astronomical (X-ray to radio), solar and
space plasma physics datasets, and the delivery of federations of
current datasets for its user communities to exploit using those
tools. <P />Whilst AstroGrid's work will be centred on existing and
future (e.g. VISTA) UK datasets, it will seek solutions to generic VO
problems and will contribute to the developing international virtual
observatory framework: AstroGrid is a member of the EU-funded <A
href="http://www.eso.org/projects/avo"> Astrophysical Virtual
Observatory </A> project, has close links to a second EU Grid
initiative, the <A href="http://www.mssl.ucl.ac.uk/grid/egso/">
European Grid of Solar Observations </A> (EGSO), and will seek an
active role in the development of the common standards on which the
international virtual observatory will rely. <P />In this paper we shall
primarily describe the concrete plans for AstroGrid's one-year Phase
A study, which will centre on: (i) the definition of detailed science
requirements through community consultation; (ii) the undertaking
of a “functionality market survey" to test the utility of existing
technologies for the VO; and (iii) a pilot programme of database
federations, each addressing different aspects of the general database
federation problem. Further information on AstroGrid can be found at
<A href="http://www.astrogrid.ac.uk"> AstroGrid </A>.
---------------------------------------------------------
Title: Non-thermal Velocities in Solar Flares [Invited]
Authors: Harra, L. K.
2002mwoc.conf..261H Altcode:
The high resolution spectroscopic information from the Bragg Crystal
Spectrometer onboard Yohkoh has provided us with new and exciting
information about flares and active regions. In particular, there has
been much work on understanding the excess line broadening above the
thermal width (known as non-thermal line broadening). We have been able
to look for the first time spectroscopically at the preflare stages. The
timings of the non-thermal velocity relative to the hard X-ray emission
has been investigated. Non-thermal velocities have been observed to
increase ten minutes before the main flares begins. Progress has been
made to locate the region of dominant non-thermal velocity. This is
difficult due to the lack of spatial resolution. A discussion will be
made on what can be expected from the EUV Imaging Spectrometer onboard
Solar B, which combines both high spatial and spectral resolution
simultaneously.
---------------------------------------------------------
Title: Multi-wavelength observations of the pre-cursor phase of
solar flares
Authors: Matthews, S.; Harra, L.; Culhane, J.
2002cosp...34E1579M Altcode: 2002cosp.meetE1579M
Observational studies of the pre-cursor phase of solar flares have
shown that there are many and varied signatures that may or may not
indicate the probable onset of a flare. Recent studies have included
results showing that in some flares the non- thermal velocity of soft
X-ray lines begins to rise up to 10 minutes before flare onset (Harra
et al., 2001), and that UV brightenings are also seen several minutes
before flare onset, at locations remote from site of the flare Hard
X-ray emission (Warren &Warshall, 2001). Combining data from Yohkoh,
SOHO and TRACE and more recent observations from RHESSI, SOHO and TRACE
we investigate the relationships between the different manifestations
of pre-flare behaviour with a view to detrmining how they affect the
flare energy release process.
---------------------------------------------------------
Title: Flare characteristics: Properties of Eruptive and Non-eruptive
events and their associations
Authors: Culhane, J.; Magee, H.; Matthews, S.; Harra, L.
2002cosp...34E1676C Altcode: 2002cosp.meetE1676C
We report studies of a sample of 64 solar flares - GOES class
A to X. Events are classed as eruptive or non-eruptive based on
whether or not accompanying CMEs were observed in SOHO LASCO or EIT
data. Associations between event parameters; duratuion, intensity,
temperature and emission measure and presence or absence of a related
CME are discussed. Intensity and duration are considered for a sample of
stellar flares and the relationship with solar flares is examined. For
a subset of the solar flare sample, the significance of the hard X-ray
spectral slope and the association with coronal waves is assessed.
---------------------------------------------------------
Title: Single source hard X-ray sources and the standard flare model
Authors: Goff, C.; Matthews, S.; Harra, L.
2002cosp...34E1082G Altcode: 2002cosp.meetE1082G
The 'standard' flare model predicts the existence of strong Hard
X-ray emission at the footpoints of the flare loop. However, Yohkoh
observations suggest that a third of events show instead only a single
source. Combining datasets which include observations from Yohkoh,
RHESSI, SOHO, TRACE and Nobeyama we compare the characteristics of
these single source events to a group of double source events with the
aim of determining whether these sources represent unresolved double
footpoints, asymmetric electron deposition due to magnetic mirroring
effects, or a genuine departure from the 'standard' model.
---------------------------------------------------------
Title: Anatomy of a Flare and Coronal Mass Ejection
Authors: Foley, C. R.; Harra, L. K.; Culhane, J. L.; Mason, K. O.;
Hori, K.; Matthews, S. A.; Iles, R. H. A.
2002mwoc.conf..253F Altcode:
In this paper we present the observations of a flare, CME and their
interaction obtained with the SOHO, Trace, and Yohkoh spacecraft. More
specifically we show evidence for wave-like motions in the Trace 171
observations, of comparable speed to those usually inferred from EIT
observations and thus termed `EIT waves'. We find that these waves
commence at the same time at which a prominence is observed to rise
within the active region and signifies the start of a gradual coronal
mass ejection. The prominence is observed with the Coronal Diagnostic
Spectrometer, on SOHO, with red and blueshifts which can only be
reconciled if the structure is rotating close to the plane of the
image with an angle of ~ 72<SUP>o</SUP>, to line of sight. During,
the impulsive phase of the flare the prominence and CME is observed
to accelerate from 190km/s to 900km/s.
---------------------------------------------------------
Title: Flare Temperature from FE XXV and CA XIX: Improved Atomic Data
Authors: Phillips, K. J. H.; Rainnie, J. A.; Harra, L. K.; Dubau,
J.; Keenan, F. P.
2002mwoc.conf..293P Altcode:
For several years flare temperatures and emission measures have
been derived from comparison of observed Yohkoh BCS spectra with
theoretical spectra derived from atomic parameters based on distorted
wave approximation. In the case of Fe XXV and Ca XIX spectra, the
main lines used in the determination are dielectronic satellite lines
(j or k as appropriate) and the resonance line w. More accurate
close-coupling calculations from the R-matrix procedure have been
available in unpublished form, and in this work these new atomic data
were substituted for the distorted wave data. The intensities of
the Fe XXV and Ca XIX lines w, x, y, and z are affected -- all are
increased. However, the differences from the previously used atomic
data are very slight. We estimate that for a given j/w ratio in Fe
XXV, for instance, the temperature estimated from the new atomic data
will be about 1MK smaller than from the existing data in the standard
Yohkoh software at temperatures of around 20MK. Smaller differences
are expected for Ca XIX at typical temperatures of 14MK. The increase
in the Fe XXV y and z line intensities tends to reduce a well-known
discrepancy in these lines (more evident in the much better resolved SMM
BCS spectra) but not by a sufficient amount to explain the discrepancy.
---------------------------------------------------------
Title: Ultraviolet spectroscopy with SOHO
Authors: Harra, L.
2002cosp...34E1466H Altcode: 2002cosp.meetE1466H
The UV spectroscopy available from SOHO has provided new and exciting
results for a wide range of phenomena observed on the Sun. Determination
of plasma parameters such as velocity, density, temperatures and
abundances have provided new physical insight into fundamental problems
in solar physics. These include magnetic reconnection, emerging flux,
quiet Sun , active region heating, the characteristics of coronal waves,
flows in solar flares, formation of the solar wind, determination of
coronal mass ejection onset and twisting of magnetic structures. This
paper will review these results, and discuss what can be achieved with
future spectroscopic instrumentation.
---------------------------------------------------------
Title: The timing of non-thermal soft X-ray emission line broadenings
in solar flares
Authors: Ranns, N. D. R.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.
2001A&A...379..616R Altcode:
We study 59 solar limb flares using the Bragg Crystal Spectrometer
(BCS) on Yohkoh and the Burst and Transient Source Experiment (BATSE)
to investigate the relative timings between the Hard X-Ray (HXR)
emission and the observed non-thermal broadenings of X-ray emission
lines (V<SUB>nt</SUB>). We show that the duration of the HXR flux
rise to maximum emission affects the relative timing of the main
V<SUB>nt</SUB> peak with respect to the main HXR peak. In ~20% of the
flares studied, secondary peaks in V<SUB>nt</SUB> are observed. These
are always associated with a strong HXR pulse and usually occur after
the associated HXR pulse. There are also flares that show a relationship
between the decay times of V<SUB>nt</SUB> and HXR flux. These results
are conducive to a causal relationship between the HXR flux and
V<SUB>nt</SUB>. We divided the sample of flares into two classes,
gradual rise and impulsive rise, depending on the shape of the HXR
lightcurve up to maximum emission. We show that the V<SUB>nt</SUB>
behaviour differs in the two classes. The implications are discussed
with a view to understanding the mechanism of V<SUB>nt</SUB> generation.
---------------------------------------------------------
Title: Material Outflows from Coronal Intensity “Dimming Regions”
during Coronal Mass Ejection Onset
Authors: Harra, Louise K.; Sterling, Alphonse C.
2001ApJ...561L.215H Altcode:
One signature of expulsion of coronal mass ejections (CMEs) from the
solar corona is the appearance of transient intensity dimmings in
coronal images. These dimmings have generally been assumed to be due
to discharge of CME material from the corona, and thus the “dimming
regions” are thought of as an important signature of the sources of
CMEs. We present spectral observations of two dimming regions at the
time of expulsion of CMEs, using the Coronal Diagnostic Spectrometer
(CDS) on the SOHO satellite. One of the dimming regions is at the
solar limb and associated with a CME traveling in the plane of the
sky, while the other region is on the solar disk and associated with
an Earth-directed “halo” CME. From the limb event, we see Doppler
signatures of ~30 km s<SUP>-1</SUP> in coronal (Fe XVI and Mg IX)
emission lines, where the enhanced velocities coincide with the
locations of coronal dimming. This provides direct evidence that the
dimmings are associated with outflowing material. We also see larger
(~100 km s<SUP>-1</SUP>) Doppler velocities in transition region (O V
and He I) emission lines, which are likely to be associated with motions
of a prominence and loops at transition region temperatures. An “EIT
wave” accompanies the disk event, and a dimming region behind the wave
shows strong blueshifted Doppler signatures of ~100 km s<SUP>-1</SUP>
in O V, suggesting that material from the dimming regions behind the
wave may be feeding the CME.
---------------------------------------------------------
Title: Eruption of a Flux Rope on the Disk of the Sun: Evidence for
the Coronal Mass Ejection Trigger?
Authors: Foley, Carl R.; Harra, Louise K.; Culhane, J. Leonard; Mason,
Keith O.
2001ApJ...560L..91F Altcode:
The first evidence of acceleration of a flux rope from the disk of the
Sun using the Coronal Diagnostic Spectrometer (CDS) on the Solar and
Heliospheric Observatory (SOHO) is presented. A distinct blueshifted
emission component (-480 km s<SUP>-1</SUP>) was observed by the EUV
spectrometer on SOHO at the start of the impulsive phase of an X2.3
flare. There is a halo coronal mass ejection associated with this
event. Based on a sequence of velocity measurements, we determine the
acceleration of the erupting material. These results are supported by
simultaneous EUV imaging data from the Transition Region and Coronal
Explorer spacecraft, which shows the projected motion of the flux
rope. The CDS spectra reveal an initial rapid acceleration phase
(3.5 km s<SUP>-2</SUP>), followed by a transition to a more gradual
acceleration (0.68 km s<SUP>-2</SUP>). This may indicate energy input
via explosive reconnection.
---------------------------------------------------------
Title: Long term evolution of a non-active region sigmoid and its
CME activity
Authors: Glover, A.; Harra, L. K.; Matthews, S. A.; Hori, K.; Culhane,
J. L.
2001A&A...378..239G Altcode:
Recent studies have considered sigmoidal features in the Solar corona to
possess a high probability of eruption. Unlike these studies which have
focussed only on active region sigmoids, the present work centres on
a large area which developed S-like morphology unconfined by a single
active region. The S-like feature formed near the central meridian
on 8th May 2000 and was observed to erupt, with an associated CME,
twice over a period of 3 days. We observe considerable CME and flaring
activity in two previous rotations, consistent with the observation
of active regions and emerging flux. We illustrate sigmoid formation
through the appearance of highly sheared soft X-ray loops overlying
an extended filament channel. This arises from the gradual diffusion
of flux associated with a large, dispersing active region over the
period of three solar rotations. This scenario is indicative of shear
build-up within the region over several rotations. The observed CMEs act
to remove helicity from the highly sheared sigmoidal feature, finally
producing an approximately potential filament channel on 10th May 2000.
---------------------------------------------------------
Title: Magnetic field configurations and the likelihood of coronal
mass ejections
Authors: Culhane, J. L.; Glover, A.; Green, L. M.; Harra, L. K.;
Matthews, S. A.; Hori, K.
2001ESASP.493..193C Altcode: 2001sefs.work..193C
No abstract at ADS
---------------------------------------------------------
Title: Velocity observations of an active region during the onset
phase of a coronal mass ejection
Authors: Harra, Louise K.; Sterling, Alphonse C.
2001ESASP.493..237H Altcode: 2001sefs.work..237H
No abstract at ADS
---------------------------------------------------------
Title: Coronal heating in the Sun and late-type stars
Authors: Harra, L. K.; Culhane, J. L.
2001Obs...121..217H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Energetics of an Active Region Observed from Helium-Like
Sulphur Lines
Authors: Watanabe, Tetsuya; Sterling, Alphonse C.; Hudson, Hugh S.;
Harra, Louise K.
2001SoPh..201...71W Altcode:
We report temperature diagnostics derived from helium-like ions of
sulphur for an active region NOAA 7978 obtained with Bragg Crystal
Spectrometer (BCS) on board the Yohkoh satellite. For the same
region we estimate conductive flux downward to the chromosphere by
the Coronal Diagnostic Spectrometer (CDS) on board the Solar and
Heliospheric Observatory (SOHO) satellite. This region appeared as a
region of soft X-ray enhancement in May 1996, underwent a period of
enhanced activity coinciding with flux emergence between 6 July and
12 July, and then continued to exist in a nearly flareless state for
several solar rotations until November 1996. Energy balance of the
non-flaring active region is basically consistent with a model of
an arcade of coronal loops having an average loop-top temperature of
4×10<SUP>6</SUP> K. Energy from flare activity during a period of flux
emergence is comparable to the energy requirements of the non-flaring
active region. However, the non-flaring energy is roughly constant
for the subsequent solar rotations following the birth of the active
region even after the flare activity essentially subsided. Energy
partition between flare activity and steady active-region heating
thus varies significantly over the lifetime of the active region,
and active-region emission cannot always be identified with flaring.
---------------------------------------------------------
Title: Coronal mass ejections and their association to active
region flaring.
Authors: Green, L. M.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.
2001SoPh..200..189G Altcode:
Since the discovery of coronal mass ejections (CMEs), flaring has been
thought to be associated in some way with the ejection in either cause
or effect. When CMEs were first discovered in the 1970s it was suggested
that they were powered by solar flares (e.g., Dryer, 1982). Research
since then (Harrison, 1986) has indicated that there is an associated
flare that occurs shortly after the CME. To investigate this further,
and making no assumption that a particular flare is causally connected
to the CME, flaring activity in nine active regions that show one or
more CME signatures has been studied for several hours before and after
CME launch. Although the initiation of the CME may occur on size scales
larger than the active region itself, definite changes are seen in
the flaring activity which may be related to the ejection. This work
indicates that the energy released from the active region magnetic
field via flaring is greater prior to the CME launch than after.
---------------------------------------------------------
Title: Radio and X ray Observations of a Limb Flare during the Max
Millennium Campaign
Authors: Lee, J.; Gallagher, P. T.; Gary, D. E.; Harra, L. K.
2001AGUSM..SP51A03L Altcode:
A powerful (GOES Class M9.8), limb flare was observed on 1999 August
20 above AR 8673 during the second Max Millennium campaign. Due to its
location on the limb as well as its strength, the flare observation
provides an ideal case of studying vertical structure of electron
acceleration and its transport. The hard X ray images from Yohkoh/HXT
along with EUV images from SoHO/EIT show an impulsive, compact double
brightening in the lower atmosphere and a hypothesis of footpoint
emission from a compact loop seems likely. In contrast, microwave
visibilities obtained using the Owens Valley Solar Array (OVSA) suggest
a region of high energy electrons high in the corona (2x 10<SUP>5</SUP>
km), requiring large loops that can act as a good trap of electrons. The
duration of radio emission is also much extended compared with the
hard X ray emission. We present this set of observations as a good
example of the trap-plus-precipitation hypothesis, and derive numbers
of electrons emitting the microwaves and hard X rays, respectively, as
a measure for the trap vs. precipitation. The derived time evolution
of electron numbers in energy space is not compatible with a simple
hypothesis of energy-independent acceleration solely under Coulomb
collisions, but instead requires an acceleration or transport process
that is highly energy-dependent.
---------------------------------------------------------
Title: Coronal heating
Authors: Harra, Louise
2001A&G....42b..18H Altcode:
Louise Harra presents a summary of a meeting at which a wealth of new
sources of data - Yohkoh, SOHO, TRACE, XMM-Newton and Chandra - is
bringing new insights to studies of solar and stellar coronal heating.
---------------------------------------------------------
Title: Nonthermal Velocity Evolution in the Precursor Phase of a
Solar Flare
Authors: Harra, L. K.; Matthews, S. A.; Culhane, J. L.
2001ApJ...549L.245H Altcode:
We present observations of two solar flares occurring in Active Region
7590 on 1993 October 3 using data from the Yohkoh spacecraft. The
hard X-ray bursts from the two flares occurred within an 18 minute
interval, with the soft X-ray emission having a shorter separation of
~5 minutes. Both flares occurred within one Yohkoh orbit, and hence
we have continuous coverage of the soft X-ray line broadening at the
peak of the first flare, reducing to the active region level of 33.5
km s<SUP>-1</SUP> in S XV (66.1 km s<SUP>-1</SUP> in Ca XIX) and then
increasing to the peak in the second flare. The rise above the active
region background level begins 11 minutes before the start of the second
flare as defined by the start of the hard X-ray emission. During this
extended rise time of V<SUB>nt</SUB>, there is no increase in the light
curves or the electron temperature. We suggest that this increase is
an indicator of turbulent changes in the active region prior to the
flare that are related to the flare trigger mechanism.
---------------------------------------------------------
Title: An Observational Test for Solar Atmospheric Heating
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Ireland, J.; Thompson,
B.; Fludra, A.; Oláh, K.; Kövári, Zs.; Harra, L. K.; Mandrini,
C. H.; Bocchialini, K.; Orlando, S.
2001IAUS..203..514V Altcode:
We study the evolution of the emissivity and heating correlated with
magnetic observables of an active region from its birth throughout
its decay during seven solar rotations (July-Dec. 1996). Taking one
"snapshot" per g:wq: Command not found. time of flares, we analyse
multi-wavelength and multi-instrument data obtained from SOHO (MDI,
EIT, CDS and SUMER), Yohkoh (SXT), GOES, SOLSTICE and 10.7 cm radio
data from DRAO, Canada. We utilise our results to test the validity
of coronal heating models. We find that models which are based on
the dissipation of stressed, current-carrying magnetic fields are in
better agreement with the observations than the models which attribute
coronal heating to the dissipation of MHD waves.
---------------------------------------------------------
Title: Properties of EUV and X-ray emission in solar active regions
Authors: Matthews, S. A.; Klimchuk, J. A.; Harra, L. K.
2001A&A...365..186M Altcode:
Using observations from the Coronal Diagnostic Spectrometer (CDS) on
SoHO and the Soft X-ray Telescope (SXT) on Yohkoh we investigate how the
spatial properties of active region emission observed in the EUV and
X-ray range varies with temperature. We examine the contrast per unit
area of the EUV emission from a number of active regions, and employ
correlation techniques and Fourier methods with which we obtain the two
dimensional power spectrum of the intensity distribution for a number of
images in emission lines formed at different temperatures. Integrating
this over polar angle we find isotropic power-law behaviour at all
temperatures in a number of topologically different active regions,
with a tendency for flatter spectra at lower temperatures. The
existence of power-law spectra indicates that there is no preferred
length scale within the regions, at least not a resolvable one, while
flatter spectra at lower temperatures indicate that the structures are
relatively smaller in this temperature range, possibly providing support
for the idea of a multi-component transition region (TR). Implications
for various heating models are discussed.
---------------------------------------------------------
Title: Quiet Sun Brightenings - Cell and Network Behaviour (CD-ROM
Directory: contribs/harra)
Authors: Harra, L.; Gallagher, T. P.; Phillips, J. J. H.
2001ASPC..223..674H Altcode: 2001csss...11..674H
No abstract at ADS
---------------------------------------------------------
Title: Location of the source of soft X-ray non-thermal line
broadenings in a solar flare
Authors: Ranns, N. D. R.; Matthews, S. A.; Harra, L. K.; Culhane, J. L.
2000A&A...364..859R Altcode:
We determine the location of the source of the non-thermal Soft
X-ray line broadenings in an M1.7 two-ribbon solar flare using
multi-wavelength observations. Using a combination of the Yohkoh Soft
X-ray Telescope (SXT), Hard X-ray Telescope (HXT), Bragg Crystal
Spectrometer (BCS) and the Transition Region and Coronal Explorer
(TRACE), we find the source of the non-thermal broadenings, at their
peak value, to be located in and above the SXR flare loops, not at the
flare loop footpoints. After eliminating the footpoints as a potential
source we discuss the likelihood that the source of non-thermally
broadened emission lines is either evaporating chromospheric plasma
or plasma above the Soft X-ray flare loop that is associated with the
flare energy release.
---------------------------------------------------------
Title: Characteristics of quiet Sun cell and network brightenings
Authors: Harra, L. K.; Gallagher, P. T.; Phillips, K. J. H.
2000A&A...362..371H Altcode:
Extreme ultraviolet observations of the quiet Sun are made with
the Coronal Diagnostic Spectrometer (cds) on board the Solar and
Heliospheric Observatory (soho). It has been previously noted that
frequent transition region brightenings occur in both the bright
network and dark cell regions. Analysing 1125 events, we determined
the characteristics of the brightenings in the cell and network
regions which include the duration, energy, and intensity increase
above the background. Network brightenings are found to be larger than
cell events occurring with a mean duration of 150 s and releasing an
average of 10<SUP>26.9</SUP> ergs per event. Cell brightenings, on the
other hand, last for an average of 96 s and release 10<SUP>25.8</SUP>
ergs per event. It has also been found that the distribution of
energy is a power-law which is different in the cell (gamma =2.5)
and network (gamma =1.5) regions. When the entire quiet Sun region
is analysed the value of gamma is 1.7. The number of events per cds
pixel is approximately the same, and a histogram of the ratio ([peak
value - background]/background) shows similar values for both the
cell and network. It is important to analyse the cell and network
regions separately in the context of coronal heating by such small
flare-like events.
---------------------------------------------------------
Title: The Energy Supply to X-ray Bright Points
Authors: McDonald, L.; Culhane, J. L.; Harra, L. K.; Matthews, S. A.
2000SoPh..196..137M Altcode:
X-ray bright points (XBPs) are usually assumed to be isolated
structures in the solar atmosphere that are powered exclusively by
magnetic reconnection. We analyse a large XBP that does not satisfy
this assumption. The XBP is observed to be connected to an active region
approximately 280 000 km away by a magnetic loop. We find that the soft
X-ray intensity and thermal energy of the XBP are very sensitive to the
existence of the magnetic loop. Both the intensity and energy decrease
significantly at the times when the loop disappears, indicating that
the loop is a medium for energy transfer from the active region to
the XBP. We deduce that the mechanism for the energy transfer is most
likely to be Alfvén or fast-mode magnetoacoustic waves created by
photospheric motions in the active region. These waves can dissipate
energy at the density gradient between the XBP and the loop via phase
mixing or resonant absorption.
---------------------------------------------------------
Title: Emerging flux as a driver for homologous flares
Authors: Ranns, N. D. R.; Harra, L. K.; Matthews, S. A.; Culhane, J. L.
2000A&A...360.1163R Altcode:
We present multi-wavelength observations of 2 M-class solar flares
observed by SoHO and Yohkoh, which appear to be homologous. By
examination of the flare loop morphology and footpoints we propose
a schematic reconnection scenario of a two loop interaction in
a quadrupolar magnetic configuration, for both flares (Machado
?; Mandrini ?). After the first flare, the combination of chance
emergence of new flux at an opportune location and a subsequent flare,
of the type described by Heyvaerts et al. (?), form a new quadrupolar
configuration in which the second flare occurred. Therefore though the
two M-class flares are homologous by definition, they appear to conform
to a scenario in which the preflare conditions are reformed after the
first flare by emerging flux, rather than models which involve the
continual shearing of a single magnetic structure.
---------------------------------------------------------
Title: The onset and association of CMEs with sigmoidal active regions
Authors: Glover, Alexi; Ranns, Neale D. R.; Harra, Louise K.; Culhane,
J. Leonard
2000GeoRL..27.2161G Altcode:
Previous studies of active regions characterised by Soft X-ray S or
inverse-S morphology [Canfield et al., 1999], have found these regions
to possess a higher probability of eruption. In such cases, CME launch
has been inferred using X-ray proxies to indicate eruption. Active
regions observed during 1997, previously categorised as both sigmoidal
and eruptive [Canfield, 1999], have been selected for further study,
incorporating SoHO-LASCO, SoHO-EIT and ground based H-alpha data. Our
results allow re-classification into three main categories; sigmoidal,
non-sigmoidal and active regions appearing sigmoidal due to the
projection of many loops. Although the reduced dataset size prevents a
statistical measure of significance, we note that regions comprising a
single S (or inverse-S) shaped structure are more frequently associated
with a CME than those classed as non-sigmoidal. This motivates the
study of a larger dataset and highlights the need for a quantitative
observational definition of the term “sigmoid”.
---------------------------------------------------------
Title: Solar activity studies through coronal X-ray observations
Authors: Harra, Louise
2000RSPTA.358..641H Altcode:
The solar corona consists of high-temperature plasma that is contained
by a wide range of magnetic field structures. The cyclic behaviour of
solar activity results in continuing evolution of these structures. This
evolution can be well studied by observing the X-ray and extreme
ultraviolet (EUV) emission from the hot plasma which delineates the
magnetic field in the corona. In this review, the X-ray images obtained
from the Yohkoh mission over more than half a solar cycle and the
information they provide about coronal evolution will be discussed. A
variety of short-term transient brightenings observed by Yohkoh,
and at EUV wavelengths by the SOHO mission, will be described and
their relevance for coronal heating evaluated. Yohkoh observations have
advanced our understanding of solar flares. These important results will
be summarized and discussed. Finally, the current view of the nature
of coronal mass ejections as deduced by Yohkoh and SOHO is presented.
---------------------------------------------------------
Title: Active region dynamics
Authors: Harra, L. K.; Matthews, S. A.; Hara, H.; Ichimoto, K.
2000ssls.work..109H Altcode:
It has been frequently observed that in solar active regions the
measured line widths are larger than those based on thermal equilibrium
widths. This excess width (characterised as non-thermal velocity,
V<SUB>nt</SUB>) has been proposed as a signature of the heating
mechanism. The behaviour of the V<SUB>nt</SUB> at coronal temperatures
has not produced consistent results with values ranging from 0 to
100 km/s. We investigate this problem by using joint observations
from Norikura Solar Observatory, Japan and the Coronal Diagnostic
Spectrometer (CDS) on SOHO. We find that values of V<SUB>nt</SUB> range
between 10-20 km/s. We analyse the dynamical bahaviour of different
temperature loops and find that for loops with log T<SUB>e</SUB> <
5.8, the variability ∝T<SUB>e</SUB><SUP>0.39</SUP>. This is comparable
to the dependence of non-thermal velocity on temperature which we have
determined to be V<SUB>nt</SUB> ∝ T<SUB>e</SUB><SUP>0.35</SUP>. This
suggests that the excess line broadening is caused by highly dynamical
behaviour in the transition region for active regions. These results
have significant implications for potential heating mechanisms and
these are discussed.
---------------------------------------------------------
Title: The spatial distribution of EUV emission in active regions
Authors: Matthews, S. A.; Klimchuk, J. A.; Harra, L. K.
2000ssls.work...53M Altcode:
The full version of this paper will be published elsewhere. We give
here only an extended abstract.
---------------------------------------------------------
Title: The Determination of Electron Densities in the Solar Atmosphere
from the 1718.56 Angstrom /1486.51 Angstrom Emission-Line Ratio in
N IV
Authors: Keenan, F. P.; Harra, L. K.; Doschek, G. A.; Cook, J. W.
1994ApJ...432..806K Altcode:
The theoretical electron density sensitive emission-line ratio
R = I(1718.56 a)/I(1486.51 A) in N IV is presented for a range of
N<SUB>e</SUB>(approximately equals 10<SUP>10</SUP> - 10<SUP>12</SUP>/cu
cm) applicable to higher density solar plasmas, such as active
regions. A comparison of these calculations with the observed values
of R of several solar features obtained with the Naval Research
Laboratory's S082B spectrograph on board Skylab reveals general
agreement between theory and observation at pointings just above the
limb, where line blends with N IV 1718.56 A should be insignificant,
which provides experimental support for the accuracy of the line
ratio calculations.
---------------------------------------------------------
Title: Coronal Electron Density Diagnostic from Fe XII
Authors: Cook, J. W.; Keenan, F. P.; Harra, L. K.; Tayal, S. S.
1994ApJ...429..924C Altcode:
We present observations of the forbidden coronal lines Fe XII 1242 A and
1349 A from active regions and from two flares, obtained by the SO82B
slit spectrograph onboard Skylab. The line intensity ratio R = I(1242
A)/I(1349 A) is sensitive to electron density. We have calculated this
ratio using recent atomic data, and obtained coronal electron densities
at T = 1.5 x 10<SUP>6</SUP> K for our observations. We find a range
in N<SUB>e</SUB> of (0.5 to 7.2) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> for
active regions, which is in good agreement with previous results from
other diagnostic ratios in this temperature range, and of approximately
(0.9 to 12) x 10<SUP>9</SUP>/cm<SUP>-3</SUP> (or higher) for flares,
which is generally low compared to previous flare results. The flare
values employ particularly weak 1349 A observations and may not be
reliable. From an observation of an active region just inside the solar
limb, giving the best coverage in our data of both line profiles, we
find a line width (FWHM) for both lines of 0.20 A, which corresponds
to a nonthermal velocity of 18 km/sec.
---------------------------------------------------------
Title: Calculated He-Like Argon Line Intensities and Comparison
with Solar Flare Spectra from the FCS Instrument on the Solar
Maximum Mission
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Zarro,
D. M.; Wilson, M.
1994emsp.conf...77H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Helium-like Argon Line Emission in Solar Flares
Authors: Phillips, K. J. H.; Harra, L. K.; Keenan, F. P.; Zarro,
D. M.; Wilson, M.
1993ApJ...419..426P Altcode:
Theoretical X-ray spectra of Ar XVII lines and Ar XVI satellites
at ∼4 Å, derived from R-matrix code and other calculations, are
compared with solar-flare observations obtained with the SMM Flat
Crystal Spectrometer. There is good agreement between the observed
line features and those in the theoretical spectra, and the comparison
leads to best-fit values of electron temperature for the observed solar
flares. We present wavelengths for the Ar XVII and some Ar XVI lines,
measured from the observed spectra, which have better precision than
previous values. In addition, the coronal Ar/S abundance is determined
from the relative intensities of Ar XVII lines to those of nearby S
XV transitions, and the value of this ratio is discussed in the light
of previous work.
---------------------------------------------------------
Title: Electron density diagnostics applicable to IUE spectra of
gaseous nebulae.
Authors: Keenan, F. P.; Feibelman, W. A.; Harra, L. K.; Conlon, E. S.;
Aggarwal, K. M.
1993uxrs.conf..341K Altcode: 1993uxsa.conf..341K
Observed values of the emission line ratios R = I(3s<SUP>2</SUP>
<SUP>1</SUP>S - 3s3p <SUP>3</SUP>P<SUB>2</SUB>)/ I(3s<SUP>2</SUP>
<SUP>1</SUP>S - 3s3p <SUP>3</SUP>P<SUB>1</SUB>) = I(2660 Å)/I(2669
Å) in Al II, R<SUB>1</SUB> = I(2s<SUP>2</SUP> <SUP>1</SUP>S -
2s2p <SUP>3</SUP>P<SUB>2</SUB>)/ I(2s<SUP>2</SUP> <SUP>1</SUP>S
- 2s2p <SUP>3</SUP>P<SUB>1</SUB>) = I(1907 Å)/I(1909 Å) in C
III, and R<SUB>2</SUB> = I(3s<SUP>2</SUP> <SUP>1</SUP>S - 3s3p
<SUP>3</SUP>P<SUB>2</SUB>)/ I(3s<SUP>2</SUP> <SUP>1</SUP>S - 3s3p
<SUP>3</SUP>P<SUB>1</SUB>) = I(1883 Å)/I(1892 Å) in Si III, measured
from high resolution spectra obtained with the International Ultraviolet
Explorer (IUE) satellite, are presented for several planetary nebulae
and symbiotic stars. Electron densities deduced from these ratios in
conjunction with new theoretical R, R<SUB>1</SUB> and R<SUB>2</SUB>
diagnostics (which are significantly different from those calculated
by previous authors), are found to be compatible, and are also in good
agreement with those derived from line ratios in other species. This
provides observational support for the accuracy of the atomic data
adopted in the line ratio calculations.
---------------------------------------------------------
Title: Spectral studies of high temperature plasmas
Authors: Harra, Louise Kim
1993PhDT.......252H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ar XVII X-ray lines emitted by solar flares.
Authors: Phillips, K. J. H.; Keenan, F. P.; Harra, L. K.; McCann, S. M.
1993uxrs.conf..579P Altcode: 1993uxsa.conf..579P
Recent calculations of electron impact excitation rates in helium-like
argon (Ar XVII) have been used to derive emission line intensities
for the resonance (1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> -
1s2p <SUP>1</SUP>P<SUB>1</SUB>), intercombination (1s<SUP>2</SUP>
<SUP>1</SUP>S<SUB>0</SUB> - 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>)
and forbidden (1s<SUP>2</SUP> <SUP>1</SUP>S<SUB>0</SUB> - 1s2s
<SUP>3</SUP>S<SUB>1</SUB>) lines that appear in the X-ray region
(≍4 Å). These have been combined with calculations of nearby
dielectronic satellites of Ar XVI to synthesize spectra that can be
compared with observations. The synthetic spectra are sensitive to
electron temperature T<SUB>e</SUB> but not electron density unless
extremely large (>10<SUP>14</SUP>cm<SUP>-3</SUP>). Comparisons have
been made using observations taken during solar flares with the Flat
Crystal Spectrometer (part of the X-ray Polychromator) on Solar Maximum
Mission and with spectra from the Alcator tokamak. The observed spectra
show good agreement with the theoretical spectra, and demonstrate the
feasibility of using Ar XVII line ratios for determining T<SUB>e</SUB>.
---------------------------------------------------------
Title: The determination of solar coronal electron temperatures from
Mg XI emission lines in SMM-FCS spectra of flares and active regions.
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Conlon,
E. S.; Kingston, A. E.
1993uxrs.conf..551H Altcode: 1993uxsa.conf..551H
Recent atomic physics calculations for Mg XI are used to derive
the electron temperature sensitive emission line ratios G =
[I(1s<SUP>2</SUP> <SUP>1</SUP>S - 1s2s <SUP>3</SUP>S) + I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s2p <SUP>3</SUP>P<SUB>1,2</SUB>)]/ I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s2p <SUP>1</SUP>P), R<SUB>1</SUB> = I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s3p <SUP>1</SUP>P)/ I(1s<SUP>2</SUP> <SUP>1</SUP>S
- 1s2p <SUP>1</SUP>P), and R<SUB>2</SUB> = I(1s<SUP>2</SUP>
<SUP>1</SUP>S - 1s4p <SUP>1</SUP>P)/ I(1s<SUP>2</SUP> <SUP>1</SUP>S -
1s2p <SUP>1</SUP>P), which are found to be significantly different from
earlier results. Values of T<SUB>e</SUB> deduced from G, R<SUB>1</SUB>
and R<SUB>2</SUB> ratios measured from solar flare and active region
spectra obtained with the Flat Crystal Spectrometer (FCS) on board the
Solar Maximum Mission (SMM) satellite are consistent. This provides
support both for the validity of the theoretical G, R<SUB>1</SUB>
and R<SUB>2</SUB> diagnostics, and for the FCS calibration curve in
the wavelength region covering the Mg XI transitions, 7.472-9.314 Å.
---------------------------------------------------------
Title: EUV lines of Mg IX as n<SUB>e</SUB>-diagnostics for high
density flares.
Authors: Harra, L. K.; Keenan, F. P.; Widing, K. G.; Conlon, E. S.
1993uxrs.conf..320H Altcode: 1993uxsa.conf..320H
Theoretical Mg IX electron density sensitive emission line ratios,
derived using electron impact excitation rates interpolated from
accurate R-matrix calculations, are presented for R<SUB>1</SUB> =
I(443.97 Å)/I(368.07 Å), R<SUB>2</SUB> = I(439.17 Å)/I(368.07 Å),
R<SUB>3</SUB> = I(443.40 Å)/I(368.07 Å) and R<SUB>4</SUB> = I(441.20
Å)/I(368.07 Å). A comparison of these with observational data for
solar flares, obtained with the Naval Research Laboratory's S082A
spectrograph on board Skylab, reveals excellent agreement between theory
and observation for R<SUB>1</SUB> and R<SUB>2</SUB>, which confirms
the usefulness of these ratios as N<SUB>e</SUB>-diagnostics for solar
flares, as well as providing experimental support for the accuracy
of the atomic data adopted in the line ratio calculations. However
the observed values of both R<SUB>3</SUB> and R<SUB>4</SUB> generally
imply unrealistically high electron densities, which is probably due
to blending in the 443.40 and 441.20 Å lines, possibly with Ar IV
443.44 Å and Mg VI/Mg VII 441.22 Å, respectively.
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Title: Energy levels and oscillator strengths for transitions in
helium-like Fe XXV and Ni XXVII.
Authors: Harra, L. K.; Boone, A. W.; Norrington, P. H.; Keenan, F. P.;
Kingston, A. E.
1993uxrs.conf..122H Altcode: 1993uxsa.conf..122H
Configuration interaction (CI) wavefunctions are used to calculate
energy levels and oscillator strengths for all significant electric
dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic
quadrupole (M2) transitions among the 1s<SUP>2</SUP>, 1s2l and 1s3l
states of He-like Fe XXV and Ni XXVII. Accurate wavefunctions are also
obtained using the fully relativistic MCDF method and similarly employed
to calculate these same energy levels and oscillator strenths. Derived
energy levels are compared to each other and with previous results,
and indicate that the MCDF method gives data which are closer to the
experimental energies. The calculated CI and MCDF A-values are found
to be in good agreement, but differ significantly in some cases from
these and previous authors.
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Title: X-Ray Emission-Line Ratios in MG XI as Electron Temperature
Diagnostics for Solar Flares and Active Regions
Authors: Keenan, F. P.; Phillips, K. J. H.; Harra, L. K.; Conlon,
E. S.; Kingston, A. E.
1992ApJ...393..815K Altcode:
Electron temperature-sensitive emission-line ratios are derived via
electron impact excitation rates for transitions in helium-like Mg
XI, calculated with the R-matrix code. These ratios are found to be
significantly different from earlier diagnostic calculations of Keenan
et al. (1984, 1991), and lead to electron temperature estimates up to
a factor of about 1.6 larger. Values of Te deduced from R<SUB>1</SUB>
and R<SUB>2</SUB> ratios measured from solar flare and active region
spectra obtained with the FCS on board the SMM satellite are consistent
and in good agreement with temperatures estimated from the observed
G ratios for these solar features. This provides support both for the
validity of the theoretical R<SUB>1</SUB> and R<SUB>2</SUB> diagnostics,
and for the FCS calibration curve in the wavelength region covering
the Mg XI transitions 7.472-9.314 A.
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Title: AI II as an electron density diagnostic for the upper
chromosphere/lower transition region in late-type stars.
Authors: Doyle, J. G.; Keenan, F. P.; Harra, L. K.; Aggarwal, K. M.;
Tayal, S. S.
1992A&A...261..285D Altcode:
The ratio of the Al II resonance line 3s2 1S-3sp 1P1 at 1670 A to the
inter-system line 3s2 1S-3s3p 3P1 at 2669 A is a useful electron density
diagnostic for N(e) greater than 10 exp 10/cu cm. However, it is also
sensitive to the adopted electron temperature, and, in fact, should
be a useful electron temperature diagnostic when Ne is not greater
than 10 exp 9/cu cm. In particular, we present observational data for
the RS CVn star II Peg and show that this ratio implies an electron
pressure substantially less than that implied from other diagnostic
line ratios but in good agreement with the pressure derived from the
C III 1176/C III 1908 ratio. We suggest additional observational and
theoretical work that may be required.
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Title: NE V Line Ratios in the EUV Spectra of Solar Flares
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Aggarwal, K. M.;
Widing, K. G.
1992ApJ...389..440K Altcode:
Theoretical line ratios involving 2s22p2-2s2p3 transitions in Ne
V between 359 and 572 A are presented. A comparison of these with
solar-flare observational data from the spectrograph on board Skylab
reveals excellent agreement between theory and experiment, with
discrepancies that average only 8 percent. This provides experimental
support for the accuracy of the atomic data adopted in the line-ratio
calculations, and in addition resolves discrepancies between theory
and observations previously found for this species. The potential
usefulness of the Ne V line ratios as electron temperature diagnostics
for the solar transition region is briefly discussed.
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Title: MG IX Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Widing, K. G.
1992ApJ...386..371K Altcode:
Attention is given to theoretical Mg IX electron density sensitive
emission-line ratios derived using electron impact excitation rates
interpolated from accurate R-matrix calculations, which are presented
for R1 = I(443.97 A)/I(368.07 A), R2 = I(439.17 A)/I(368.07 A), R3 =
I(368.07 A)/I(443.07 A), and R4 = I(441.20 A)/I(368.07 A). A comparison
of these with observational data for solar flares on board Skylab
reveals excellent agreement between theory and observation for R1 and
R2, which confirms the usefulness of these ratios as Ne-diagnostics for
solar flares, as well as providing experimental support for the accuracy
of the atomic data adopted in the line ratio calculations. The observed
values of both R3 and R4 generally imply unrealistically high electron
densities, which is argued to be due to blending in the 443.40- and
441.20-A lines, probably with Ar IV 443.44 A and Mg VI/Mg VII 441.22
A, respectively.
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Title: AL II Emission-Line Strengths in Low-Density Astrophysical
Plasmas
Authors: Keenan, F. P.; Harra, L. K.; Aggarwal, K. M.; Feibelman, W. A.
1992ApJ...385..375K Altcode:
Theoretical values of the emission-line ratio R are derived for the
transitions 3s2 1S-3s3p 3P2 and 3s2 1S-3s3p 3P1 in Al II, at 2660 and
2669 A, respectively. These ratios are compared with IUE observations
of the planetary nebula NGC 7027 and the symbiotic star RR Tel, to
illustrate the usefulness of the R as an electron density diagnostics. A
value of R = 0.72 was deduced for NGC 7027, which implies log Ne =
4.2 for Te = 14,000 K. This is consistent with densities deduced
earlier for this planetary nebula.
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Title: C IV Line Ratios in the Sun
Authors: Keenan, F. P.; Conlon, E. S.; Harra, L. K.; Burke, V. M.;
Widing, K. G.
1992ApJ...385..381K Altcode:
Theoretical electron temperature-sensitive emission-line ratios are
calculated with R-matrix analysis of electron-impact excitation
rates for transitions in C IV. Two of the emission-line ratios
are found to agree with observational data on the sun taken with
a slitless spectrograph aboard Skylab, and the two remaining lines
have inaccuracies that can be attributed to blending of the 312.43
A line. The agreement between the observational and analytical data
lends credence to the accuracy of the atomic data used in the analysis.
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Title: X-ray emission-line ratios in He-like ions as
electron-temperature diagnostics for solar flares and active regions
(abstract)
Authors: Harra, L. K.; Phillips, K. J. H.; Keenan, F. P.; Bromage,
B. J. I.; McCann, S. M.
1992sccw.conf..144H Altcode:
No abstract at ADS
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Title: Improved Line Ratio Calculations Involving Delta N = 1
(2--3) Transitions in O V and a Reanalysis of SKYLAB Observations
of Solar Flares
Authors: Keenan, F. P.; Dufton, P. L.; Harra, L. K.; Conlon, E. S.;
Berrington, K. A.; Kingston, A. E.; Widing, K. G.
1991ApJ...382..349K Altcode:
R-matrix calculations of electron-impact-excitation rates in O
V are used to rederive theoretical electron-density diagnostic
emission-line ratios involving transitions between the n = 2 and 3
levels, which includes lines at 192.80, 192.90, 215.10, 215.25, 220.35,
and 248.46 A. A comparison of these diagnostics with observational
data for two solar flares obtained with the spectrograph on board
Skylab reveals better agreement between theory and observation than was
found previously. This provides experimental support for the improved
accuracy of the atomic data employed in the present analysis.
