explanation blue bibcodes open ADS page with paths to full text
Author name code: schmit
ADS astronomy entries on 2022-09-14
=author:"Schmit, Donald" OR =author:"Schmit, Donald J." OR =author:"Schmit, D.J."
---------------------------------------------------------
Title: First Imaging Spectroscopy of 92-115 Angstrom Solar Soft
X-rays by EUNIS: Implications for Solar Coronal Heating
Authors: Brosius, Jeffrey; Daw, Adrian; Rabin, Douglas; Landi, Enrico;
Schmit, Donald
2021AGUFMSH12B..04B Altcode:
The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS)
sounding rocket waslaunched from White Sands Missile Range, NM, on
May 18, 2021. The instrumentcomprised a pair of coaligned imaging
spectrographs, one of which observed solarline emission in first
order at wavelengths between 525 and 639 A, and the secondof which
observed line emission in third order at wavelengths between 92 and
115 Aand in first order between 277 and 345 A. Images of AR 12824,
quiet-sun area, andoff-limb area were obtained by rastering the slits
over the selected targets. Thisis the first time that solar imaging
spectroscopy has been performed in the 92-115A soft X-ray range. This
waveband was selected to (1) observe Fe XVIII 93.932 and103.948 A
and Fe XIX 108.355 A line emission in a quiescent active region, and
(2)explore a relatively unobserved portion of the solar electromagnetic
spectrum. Theinstrument performed well during its 6-minute observing
run. We report preliminaryresults on observations of Fe XVIII and Fe
XIX in the quiescent active region, anddiscuss implications for the
nanoflare model of solar coronal heating. EUNIS wassupported by NASA
Heliophysics Low Cost Access to Space award 13-HTIDS13_2-0074.
---------------------------------------------------------
Title: A Novel Integral Field Spectrograph Design for taking
High-Cadence Spectral Solar Images: SNIFS
Authors: Knoer, Vicki; Chamberlin, Phillip; Daw, Adrian; Gong, Qian;
Milligan, Ryan; Polito, Vanessa; Schmit, Donald
2021AGUFMSH55B1837K Altcode:
Many features on the sun such as flares and nanoflares are highly
dynamic and change over the course of seconds. This is at least an order
of magnitude faster than our current ability to 2D spectrally image the
sun. This difference in time scale has made it difficult to study some
of the sun's faster-changing features. The newly designed Solar eruptioN
Integral Field Spectrograph (SNIFS) is an extreme ultraviolet (EUV)
integral field spectrograph which will be able to take spectral images
of the sun at a 1 second time cadence. The game-changing innovations
which allow a faster cadence include a fast-readout CMOS detector
and an array of mirrorlets to focus the incoming light into a square
array spatial pixels, the spectrum for each of which will be measured
simultaneously. The optical path is doubled in order to view both active
network and flaring sun. This new optical design will allow high-cadence
spectral imaging of the sun which will contribute to our understanding
of energy and mass transport in the chromosphere and transition region.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: The Solar eruptioN Integral Field Spectrograph (SNIFS)
Sounding Rocket
Authors: Chamberlin, P. C.; Schmit, D. J.; Daw, A. N.; Polito, V.;
Gong, Q.; Milligan, R. O.
2020AGUFMSH056..03C Altcode:
The lower solar atmosphere is temporally dynamic and spatially
inhomogeneous, and it is becoming increasingly clear that this
complex activity must be measured and quantified if we are to fully
understand how mass and energy are transported into the corona. The
Solar eruptioN Integral Field Spectrograph (SNIFS) sounding rocket is
designed to break new ground by using a unique set of capabilities to
probe the most vexingly complex region of the solar atmosphere, the
chromosphere. Hydrogen Lyman-alpha (Ly-α; 121.6 nm) is the brightest
line in the solar UV spectrum, it is energetically one of the most
important. Using radiation transfer models, we can use the observed line
profiles to reconstruct the transit of these photon through the solar
atmosphere and understand the plasma from which they came. SNIFS will
observe not only Ly-ɑ, but the nearby Si III and O V emissions, two
transition regions lines that allow us to observe how the chromosphere
connects with upper atmosphere. The SNIFS rocket mission has a primary
objective to explore the energetics and dynamics of chromosphere using
a next-generation solar spectral imager. <P />SNIFS will be the first
of its kind: a solar ultraviolet integral field spectrograph (IFS;
Chamberlin and Gong, 2016). SNIFS technology will revolutionize solar
observations by obtaining high cadence 3D information simultaneously:
two spatial dimensions and one spectral dimensions.SNIFS utilizes a
novel optical design to simultaneously observe a 32 x 32 arcsec field
of view with 0.45 arcsec pixels, with a spectral resolution of 66mÅ
and at 1 s cadence. The SNIFS design employs, for the first time in
a spaceflight instrument as a technology development, a 72x72 element
2D array of reflecting and focusing mirrorlets, allowing IFS concepts
to move down into EUV wavelengths. This mirrorlet array is placed
at the imaging plane of the telescope, similar to the location of
a slit in a traditional imaging slit-spectrometer design. After the
mirrorlet in the optical path, a focusing grating will then produce
a high-resolution spectrum for each spatial element defined by the
mirrorlet elements. SNIFS's IFS technology is truly a game-changing
instrument needed for future solar physics missions, and was recently
selected and funded by NASA to fly in Spring of 2024.
---------------------------------------------------------
Title: What Is the Source of Quiet Sun Transition Region Emission?
Authors: Schmit, D. J.; De Pontieu, Bart
2016ApJ...831..158S Altcode: 2016arXiv160807620S
Dating back to the first observations of the on-disk corona, there has
been a qualitative link between the photosphere’s magnetic network
and enhanced transition-temperature plasma emission. These observations
led to the development of a general model that describes emission
structures through the partitioning of the atmospheric volume with
different magnetic loop geometries that exhibit different energetic
equilibria. Does the internetwork produce transition-temperature
emission? What fraction of network flux connects to the corona? How
does quiet Sun emission compare with low-activity Sun-like stars? In
this work, we revisit the canonical model of the quiet Sun, with
high-resolution observations from the Interface Region Imaging
Spectrograph (IRIS) and HMI in hand, to address those questions. We
use over 900 deep exposures of Si IV 1393 Å from IRIS along with
nearly simultaneous HMI magnetograms to quantify the correlation
between transition-temperature emission structures and magnetic
field concentrations through a number of novel statistics. Our
observational results are coupled with analysis of the Bifrost MHD
model and a large-scale potential field model. Our results paint a
complex portrait of the quiet Sun. We measure an emission signature
in the distant internetwork that cannot be attributed to network
contribution. We find that the dimmest regions of emission are not
linked to the local vertical magnetic field. Using the MHD simulation,
we categorize the emission contribution from cool mid-altitude loops
and high-altitude coronal loops and discuss the potential emission
contribution of spicules. Our results provide new constraints on the
coupled solar atmosphere so that we can build on our understanding
of how dynamic thermal and magnetic structures generate the observed
phenomena in the transition region.
---------------------------------------------------------
Title: Connecting Photospheric Magnetic Fields and Transition
Temperature Plasma Emission
Authors: Schmit, Donald
2016SPD....47.0332S Altcode:
The connectivity of quiet sun magnetic fields is not well
understood. One observational obstacle to probe this question
has been the sparse spectral observations spanning the transition
temperatures (3×10<SUP>4</SUP> K< T < 1×10<SUP>5</SUP>K)
between the chromosphere and corona. The Si IV lines observed by IRIS
provide a rich dataset to address the structure of the cool quiet
sun. We use over 900 deep exposures from IRIS to map the correlation
between transition-temperature emission structures and magnetic field
concentrations. Ultimately, our aim is to discern the topology and
energetic equilibrium of the magnetic structures that span the quiet
sun. We use both a potential field model and a snapshot of the Bifrost
3D MHD simulation to interpret our emission data. In a broad sense, we
find there is a clear correlation between magnetic fields and strong
Si IV emission. However, more pointed statistics suggest that the
relationship is quite complex. We do not find evidence for cool loops
longer than 3 Mm in length, but we see ubiquitous, smooth emission
nearly everywhere in the quiet sun. Emission voids on scales larger
than 8 Mm cannot be well explained by their proximity to magnetic
fields. This evidence suggests that weak-field transition-temperature
loops contribute significantly to quiet sun transition-temperature
emission measure, and evolutionary effects likely play a role in
structuring the magnetic atmosphere.
---------------------------------------------------------
Title: Cool Plasma Observed in the FUV using IRIS
Authors: Schmit, D. J.; Innes, D.
2014AGUFMSH51C4177S Altcode:
Cool plasma in the outer solar atmosphere is commonly observed in
prominences and coronal rain. Theory suggests that these phenomena are
related to cooling, and analysis of observations provides a constraint
on the time-dependent energetics of the chromosphere and corona. Using
the IRIS SG and SJI datasets, we discuss new observations of molecular
absorption features in the Si IV emission lines near 1400A. The
presence of molecules above the transition region provides an extreme
example of complex structure and dynamics at the chromosphere-corona
interface. There are two morphological models that can explain the
absorption features: cool plasma hundreds of kilometers above the
photosphere or a localized transition region deeply embedded in the
photosphere. We discuss the merit of these scenarios and introduce
complementary IRIS observations of inverted temperature structure
in Ellerman bombs and diffuse Si I continuum absorption above active
region loops.
---------------------------------------------------------
Title: Molecular absorption in transition region spectral lines
Authors: Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.;
Jaeggli, S.
2014A&A...569L...7S Altcode: 2014arXiv1409.1702S
<BR /> Aims: We present observations from the Interface Region Imaging
Spectrograph (IRIS) of absorption features from a multitude of cool
atomic and molecular lines within the profiles of Si IV transition
region lines. Many of these spectral lines have not previously
been detected in solar spectra. <BR /> Methods: We examined spectra
taken from deep exposures of plage on 12 October 2013. We observed
unique absorption spectra over a magnetic element which is bright in
transition region line emission and the ultraviolet continuum. We
compared the absorption spectra with emission spectra that is
likely related to fluorescence. <BR /> Results: The absorption
features require a population of sub-5000 K plasma to exist above
the transition region. This peculiar stratification is an extreme
deviation from the canonical structure of the chromosphere-corona
boundary. The cool material is not associated with a filament or
discernible coronal rain. This suggests that molecules may form in
the upper solar atmosphere on small spatial scales and introduces a
new complexity into our understanding of solar thermal structure. It
lends credence to previous numerical studies that found evidence
for elevated pockets of cool gas in the chromosphere. <P />Movies
associated to Figs. 1 and 2 are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201424432/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: On the Structure and Evolution of a Polar Crown
Prominence/Filament System
Authors: Panesar, N. K.; Innes, D. E.; Schmit, D. J.; Tiwari, S. K.
2014SoPh..289.2971P Altcode: 2014arXiv1402.4989P; 2014SoPh..tmp...50P
Polar crown prominences, that partially circle the Sun's poles between
60° and 70° latitude, are made of chromospheric plasma. We aim to
diagnose the 3D dynamics of a polar crown prominence using high-cadence
EUV images from the Solar Dynamics Observatory (SDO)/AIA at 304,
171, and 193 Å and the Ahead spacecraft of the Solar Terrestrial
Relations Observatory (STEREO-A)/EUVI at 195 Å. Using time series
across specific structures, we compare flows across the disk in
195 Å with the prominence dynamics seen on the limb. The densest
prominence material forms vertical columns that are separated by many
tens of Mm and connected by dynamic bridges of plasma that are clearly
visible in 304/171 Å two-colour images. We also observe intermittent
but repetitious flows with velocity 15 km s<SUP>−1</SUP> in the
prominence that appear to be associated with EUV bright points on
the solar disk. The boundary between the prominence and the overlying
cavity appears as a sharp edge. We discuss the structure of the coronal
cavity seen both above and around the prominence. SDO/HMI and GONG
magnetograms are used to infer the underlying magnetic topology. The
evolution and structure of the prominence with respect to the magnetic
field seems to agree with the filament-linkage model.
---------------------------------------------------------
Title: Jets and Bombs: Characterizing IRIS Spectra
Authors: Schmit, Donald; Innes, Davina
2014AAS...22432309S Altcode:
For almost two decades, SUMER has provided an unique perspective on
explosive events in the lower solar atmosphere. One of the hallmark
observations during this tenure is the identification of quiet sun
bi-directional jets in the lower transition region. We investigate
these events through two distinct avenues of study: a MHD model for
reconnection and the new datasets of the Interface Region Imaging
Spectrograph (IRIS). Based on forward modeling optically thin spectral
profiles, we find the spectral signatures of reconnection can vary
dramatically based on viewing angle and altitude. We look to the
IRIS data to provide a more complete context of the chromospheric
and coronal environment during these dynamic events. During a joint
IRIS-SUMER observing campaign, we observed spectra of multiple jets,
a small C flare, and an Ellerman bomb event. We discuss the questions
that arise from the inspection of these new data.
---------------------------------------------------------
Title: The Formation of a Cavity in a 3D Flux Rope
Authors: Schmit, Donald; Gibson, Sarah
2014IAUS..300..147S Altcode: 2013arXiv1311.2384S
There are currently no three dimensional numerical models which
describe the magnetic and energetic formation of prominences
self-consistently. Consequently, there has not been significant progress
made in understanding the connection between the dense prominence
plasma and the coronal cavity. We have taken an ad-hoc approach to
understanding the energetic implications of the magnetic models of
prominence structure. We extract one dimensional magnetic field lines
from a 3D MHD model of a flux rope and solve for hydrostatic balance
along these field lines incorporating field-aligned thermal conduction,
uniform heating, and radiative losses. The 1D hydrostatic solutions for
density and temperature are then mapped back into three dimensional
space, which allows us to consider the projection of multiple
structures. We find that the 3D flux rope is composed of several
distinct field line types. A majority of the flux rope interior field
lines are twisted but not dipped. These field lines are density-reduced
relative to unsheared arcade field lines. We suggest the cavity may
form along these short interior field lines which are surrounded by a
sheath of dipped field lines. This geometric arrangement would create a
cavity on top of a prominence, but the two structures would not share
field lines or plasma.
---------------------------------------------------------
Title: Prominence Mass Supply and the Cavity
Authors: Schmit, Donald J.; Gibson, S.; Luna, M.; Karpen, J.; Innes, D.
2013ApJ...779..156S Altcode: 2013arXiv1311.2382S
A prevalent but untested paradigm is often used to describe the
prominence-cavity system: the cavity is under-dense because it
is evacuated by supplying mass to the condensed prominence. The
thermal non-equilibrium (TNE) model of prominence formation offers
a theoretical framework to predict the thermodynamic evolution of
the prominence and the surrounding corona. We examine the evidence
for a prominence-cavity connection by comparing the TNE model with
diagnostics of dynamic extreme ultraviolet (EUV) emission surrounding
the prominence, specifically prominence horns. Horns are correlated
extensions of prominence plasma and coronal plasma which appear
to connect the prominence and cavity. The TNE model predicts that
large-scale brightenings will occur in the Solar Dynamics Observatory
Atmospheric Imaging Assembly 171 Å bandpass near the prominence that
are associated with the cooling phase of condensation formation. In
our simulations, variations in the magnitude of footpoint heating
lead to variations in the duration, spatial scale, and temporal offset
between emission enhancements in the other EUV bandpasses. While these
predictions match well a subset of the horn observations, the range of
variations in the observed structures is not captured by the model. We
discuss the implications of our one-dimensional loop simulations for
the three-dimensional time-averaged equilibrium in the prominence
and the cavity. Evidence suggests that horns are likely caused by
condensing prominence plasma, but the larger question of whether this
process produces a density-depleted cavity requires a more tightly
constrained model of heating and better knowledge of the associated
magnetic structure.
---------------------------------------------------------
Title: Diagnosing the Prominence-Cavity Connection
Authors: Schmit, Donald J.; Gibson, Sarah
2013ApJ...770...35S Altcode: 2013arXiv1304.7595S
Prominences and cavities are ubiquitously observed together, but
the physical link between these disparate structures has not been
established. We address this issue by using dynamic emission in the
extreme ultraviolet to probe the connections of these structures. The
SDO/AIA observations show that the cavity exhibits excessive emission
variability compared to the surrounding quiet-Sun streamer, particularly
in the 171 Å bandpass. We find that this dynamic emission takes the
form of coherent loop-like brightening structures which emanate from the
prominence into the central cavity. The geometry of these structures,
dubbed prominence horns, generally mimics the curvature of the cavity
boundary. We use a space-time statistical analysis of two cavities in
multiple AIA bandpasses to constrain the energetic properties of 45
horns. In general, we find there is a positive correlation between the
light curves of the horns in the 171 Å and 193 Å bandpasses; however,
the 193 Å emission is a factor of five weaker. There is also a strong
correlation between structural changes to the prominence as viewed in
the He II 304 Å bandpass and the enhanced 171 Å emission. In that
bandpass, the prominence appears to extend several megameters along
the 171 Å horn where we observe co-spatial, co-temporal 304 Å and
171 Å emission dynamics. We present these observations as evidence
of the magnetic and energetic connection between the prominence and
the cavity. Further modeling work is necessary to explain the physical
source and consequences of these events, particularly in the context of
the traditional paradigm: the cavity is underdense because it supplies
mass to the overdense prominence.
---------------------------------------------------------
Title: Magnetic structure and flows in coronal prominence cavities
Authors: Gibson, S. E.; Bak-Steslicka, U.; Forland, B.; Schmit, D. J.
2013AGUSMSH23B..04G Altcode:
Prominence cavities provide deep insight into the storage and release
of magnetic energy in the solar corona. Recent studies have yielded
a variety of observations that provide new constraints on models of
prominences, cavities, and coronal mass ejections. In particular,
a survey of SDO/AIA extreme-ultraviolet cavities has demonstrated
that a tear-shaped morphology is a predictor of impending eruption,
indicating that a change in topology may play a role in their
destabilization. Other studies utilizing extreme-ultraviolet and
infrared observations have shown both circulating plane-of-sky flows
and a "bulls-eye" pattern in line-of-sight flows within cavities,
indicating a central magnetic axis. A comparison of coronal flows
within the cavity and flows associated with the embedded prominence
demonstrate both spatial and temporal correlations, indicating
they are both magnetically and thermodynamically connected. Finally,
coronal magnetometric observations show a characteristic "rabbit-head"
signature in linear polarization within polar-crown-prominence cavities,
indicating twisted or sheared magnetic field at the heart of the
cavity. All of these observations lend credence to the model of the
cavity as a magnetic flux rope: both as a long-lived MHD equilibrium
state and as a key component in the ultimate destabilization and
eruption of coronal mass ejections.
---------------------------------------------------------
Title: Temperature and Extreme-ultraviolet Intensity in a Coronal
Prominence Cavity and Streamer
Authors: Kucera, T. A.; Gibson, S. E.; Schmit, D. J.; Landi, E.;
Tripathi, D.
2012ApJ...757...73K Altcode:
We analyze the temperature and EUV line emission of a coronal cavity and
surrounding streamer in terms of a morphological forward model. We use a
series of iron line ratios observed with the Hinode Extreme-ultraviolet
Imaging Spectrograph (EIS) on 2007 August 9 to constrain temperature
as a function of altitude in a morphological forward model of the
streamer and cavity. We also compare model predictions to the EIS EUV
line intensities and polarized brightness (pB) data from the Mauna
Loa Solar Observatory (MLSO) Mark 4 K-coronameter. This work builds
on earlier analysis using the same model to determine geometry of
and density in the same cavity and streamer. The fit to the data
with altitude-dependent temperature profiles indicates that both
the streamer and cavity have temperatures in the range 1.4-1.7
MK. However, the cavity exhibits substantial substructure such
that the altitude-dependent temperature profile is not sufficient to
completely model conditions in the cavity. Coronal prominence cavities
are structured by magnetism so clues to this structure are to be found
in their plasma properties. These temperature substructures are likely
related to structures in the cavity magnetic field. Furthermore,
we find that the model overestimates the EUV line intensities by a
factor of 4-10, without overestimating pB. We discuss this difference
in terms of filling factors and uncertainties in density diagnostics
and elemental abundances.
---------------------------------------------------------
Title: Diagnosing the Prominence-Cavity Connection
Authors: Schmit, Donald; Gibson, S.
2012AAS...22052102S Altcode:
Prominences are regions of cool, dense plasma which are suspended
above the solar limb within the much hotter and more rarefied solar
corona. The coronal environment surrounding the prominence is often
observed as a elliptical region of reduced density (compared to the
ambient corona) known as a cavity. To date, the cavity has been a
neglected constraint on the prominence system. In this research,
I probe the magnetic structural connection between the cavity and
prominence and the potential role the cavity plays in the mass
and energy balance of the prominence. Observationally, I use the
Hinode/EIS and SDO/AIA datasets to extract dynamic substructure from the
cavity. The temperature-sensitivities of these data are used to diagnose
the interaction of plasma in the prominence and in the surrounding
corona.These observational dynamics present a viable constraint on
prominence models in two ways. Structurally, the morphology of the
extract substructure can be compared to the 3D models of prominence
support. Energetically, the spatial and temporal signature of EUV
dynamics can be compared to the thermal non-equilibrium model for
prominence mass supply. This joint approach systematically addresses
the two largest questions in prominence research: how is the prominence
mass supported and where does it come from.
---------------------------------------------------------
Title: Temperature Structure of a Coronal Cavity and Streamer
Authors: Kucera, Therese A.; Gibson, S. E.; Schmit, D. J.; Landi,
E.; Tripathi, D.
2012AAS...22052113K Altcode:
We analyze the temperature and EUV line emission of a coronal cavity and
surrounding streamer in terms of a morphological forward model. We use a
series of iron line ratios observed with the Hinode Extreme-ultraviolet
Imaging Spectrograph (EIS) on 2007 Aug. 9 to constrain temperature
as a function of altitude in a morphological forward model of the
streamer and cavity. We also compare model prediction of the EIS EUV
line intensities and polarized brightness (pB) data from the Mauna Loa
Solar Observatory (MLSO) MK4. This work builds on earlier analysis using
the same model to determine geometry of and density in the same cavity
and streamer (Gibson et al. 2010 and Schmit and Gibson 2011). The fit
to the data with altitude dependent temperature profiles indicates that
both the streamer and cavity have temperatures in the range 1.4-1.7
MK. However, the cavity exhibits substantial substructure such that the
altitude dependent temperature profile is not sufficient to completely
model conditions in the cavity. This work is supported in part by the
NASA SHP program
---------------------------------------------------------
Title: Diagnosing the Prominence-Cavity Connection
Authors: Schmit, Donald; Gibson, Sarah
2012decs.confE...7S Altcode:
Prominences are regions of cool, dense plasma which are suspended
above the solar limb within the much hotter and more rarefied solar
corona. The coronal environment surrounding the prominence is often
observed as an elliptical region of reduced density (compared to
the ambient corona) known as a cavity. The fundamental problems in
prominence physics are the magnetic support of condensed plasma and the
mass-source of those condensations. We use the SDO/AIA dataset to probe
the correlated dynamics in between the cool prominence and the coronal
cavity. These dynamics are explained through the 1D modeling of the
radiative instability. The magnetic field inferred from these dynamics
is also compared to the 3D MHD models of prominence support. Through
this joint approach, the dynamic nature of the prominence system is
brought into sharp focus for the first time.
---------------------------------------------------------
Title: Diagnosing the Prominence-Cavity Connection in the Solar Corona
Authors: Schmit, D. J.
2012PhDT.......416S Altcode:
The energetic equilibrium of the corona is described by a balance of
heating, thermal conduction, and radiative cooling. Prominences can be
described by the thermal instability of coronal energy balance which
leads to the formation of cool condensations. Observationally, the
prominence is surrounded by a density depleted elliptical structure
known as a cavity. In this dissertation, we use extreme ultraviolet
remote sensing observations of the prominence-cavity system to
diagnose the static and dynamic properties of these structures. The
observations are compared with numerical models for the time-dependent
coronal condensation process and the time-independent corona-prominence
magnetic field. To diagnose the density of the cavity, we construct
a three-dimensional structural model of the corona. This structural
model allows us to synthesize extreme ultraviolet emission in the
corona in a way that incorporates the projection effects which arise
from the optically thin plasma. This forward model technique is used
to constrain a radial density profile simultaneously in the cavity
and the streamer. We use a χ2 minimization to find the density
model which best matches a density sensitive line ratio (observed
with Hinode/Extreme ultraviolet Imaging Spectrometer) and the white
light scattered intensity (observed with Mauna Loa Solar Observatory
MK4 coronagraph). We use extreme ultraviolet spectra and spectral
images to diagnose the dynamics of the prominence and the surrounding
corona. Based on the doppler shift of extreme ultraviolet coronal
emission lines, we find that there are large regions of flowing plasma
which appear to occur within cavities. These line of sight flows have
speeds of 10 km/s-1 and projected spatial scales of 100 Mm. Using the
Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA)
dataset, we observe dynamic emission from the prominence-cavity
system. The SDO/AIA dataset observes multiple spectral bandpasses
with different temperature sensitivities. Time-dependent changes in
the observed emission in these bandpass images represent changes in
the thermodynamic properties of the emitting plasma. We find that the
coronal region surrounding the prominence exhibits larger intensity
variations (over tens of hours of observations) as compared to the
streamer region. This variability is particularly strong in the cool
coronal emission of the 171Å bandpass. We identify the source of this
variability as strong brightening events that resemble concave-up loop
segments and extend from the cool prominence plasma. Magnetic field
lines are the basic structural building block of the corona. Energy and
pressure balance in the corona occur along magnetic field lines. The
large-scale extreme ultraviolet emission we observe in the corona is a
conglomerate of many coronal loops projected along a line of sight. In
order to calculate the plasma properties at a particular point in the
corona, we use one-dimensional models for energy and pressure balance
along field lines. In order to predict the extreme ultraviolet emission
along a particular line of sight, we project these one-dimensional
models onto the three-dimensional magnetic configuration provided by a
MHD model for the coronal magnetic field. These results have allowed
us to the establish the first comprehensive picture on the magnetic
and energetic interaction of the prominence and the cavity. While the
originally hypothesis that the cavity supplies mass to the prominence
proved inaccurate, we cannot simply say that these structures are not
related. Rather our findings suggest that the prominence and the cavity
are distinct magnetic substructures that are complementary regions of
a larger whole, specifically a magnetic flux rope. (Abstract shortened
by UMI.).
---------------------------------------------------------
Title: Diagnosing the Prominence-Cavity Connection
Authors: Schmit, D. J.; Gibson, S. E.
2011AGUFMSH43B1947S Altcode:
The magnetic field is thought to play a central role in both the
support of prominence plasma as well as the thermodynamic isolation of
the surrounding cavity. We use the statistical goldmine of the SDO/AIA
dataset to probe for the first time the dynamical link between these
related structures. These observations are compared to the 3D magnetic
geometries predicted by MHD models. The dynamic features are explained
within the context of 1D field-aligned momentum and energy imbalance.
---------------------------------------------------------
Title: Forward Modeling Cavity Density: A Multi-instrument Diagnostic
Authors: Schmit, D. J.; Gibson, S. E.
2011ApJ...733....1S Altcode:
The thermodynamic properties of coronal prominence cavities present a
unique probe into the energy and mass budget of prominences. Using
a three-dimensional morphological model, we forward model the
polarization brightness and extreme-ultraviolet (EUV) emission of a
cavity and its surrounding streamer. Using a genetic algorithm, we
find the best-fit density model by comparing the models to Mauna Loa
Solar Observatory MK4 and Hinode EUV Imaging Spectrometer data. The
effect of temperature variations on the derived density is also
measured. We have measured the density inside a cavity down to 1.05 R
<SUB>sun</SUB> with height-dependent error bars. Our forward modeling
technique compensates for optically thin projection effects. This
method provides a complementary technique to traditional line ratio
diagnostics that is useful for diffuse off-limb coronal structures.
---------------------------------------------------------
Title: Temperature Structure of a Coronal Cavity
Authors: Kucera, Therese A.; Gibson, S. E.; Schmit, D. J.
2011SPD....42.1833K Altcode: 2011BAAS..43S.1833K
We analyze the temperature structure of a coronal cavity observed in
Aug. 2007. Coronal cavities are long, low-density structures located
over filament neutral lines and are often seen as dark elliptical
features at the solar limb in white light, EUV and X-rays. When
these structures erupt they form the cavity portions of CMEs. It is
important to establish the temperature structure of cavities in order
to understand the thermodynamics of cavities in relation to their
three-dimensional magnetic structure. <P />To analyze the temperature
we compare temperature ratios of a series of iron lines observed by
the Hinode/EUV Imaging Spectrometer (EIS). We also use those lines
to constrain a forward model of the emission from the cavity and
streamer. The model assumes a coronal streamer with a tunnel-like
cavity with elliptical cross-section and a Gaussian variation of height
along the tunnel length. Temperature and density can be varied as
a function of altitude both in the cavity and streamer. The general
cavity morphology and the cavity and streamer density have already
been modeled using data from STEREO's SECCHI/EUVI and Hinode/EIS
(Gibson et al 2010 and Schmit & Gibson 2011).
---------------------------------------------------------
Title: Three-dimensional morphology of a coronal prominence cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
Toma, G.; Hao, J.; Hill, S. M.; Hudson, H. S.; Marque, C.; McIntosh,
P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
Sterling, A.; Tripathi, D.; Williams, D. R.; Zhang, M.
2010AGUFMSH51A1667G Altcode:
We present a three-dimensional density model of coronal prominence
cavities, and a morphological fit that has been tightly constrained
by a uniquely well-observed cavity. Observations were obtained as part
of an International Heliophysical Year campaign by instruments from a
variety of space- and ground-based observatories, spanning wavelengths
from radio to soft-X-ray to integrated white light. From these data
it is clear that the prominence cavity is the limb manifestation of
a longitudinally-extended polar-crown filament channel, and that
the cavity is a region of low density relative to the surrounding
corona. As a first step towards quantifying density and temperature
from campaign spectroscopic data, we establish the three-dimensional
morphology of the cavity. This is critical for taking line-of-sight
projection effects into account, since cavities are not localized in the
plane of the sky and the corona is optically thin. We have augmented
a global coronal streamer model to include a tunnel-like cavity with
elliptical cross-section and a Gaussian variation of height along
the tunnel length. We have developed a semi-automated routine that
fits ellipses to cross-sections of the cavity as it rotates past the
solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI)
observations from the two Solar Terrestrial Relations Observatory
(STEREO) spacecraft. This defines the morphological parameters of our
model, from which we reproduce forward-modeled cavity observables. We
find that cavity morphology and orientation, in combination with the
viewpoints of the observing spacecraft, explains the observed variation
in cavity visibility for the east vs. west limbs.
---------------------------------------------------------
Title: Three-dimensional Morphology of a Coronal Prominence Cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
Toma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marqué, C.; McIntosh,
P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.;
Zhang, M.
2010ApJ...724.1133G Altcode:
We present a three-dimensional density model of coronal prominence
cavities, and a morphological fit that has been tightly constrained
by a uniquely well-observed cavity. Observations were obtained as part
of an International Heliophysical Year campaign by instruments from a
variety of space- and ground-based observatories, spanning wavelengths
from radio to soft X-ray to integrated white light. From these data
it is clear that the prominence cavity is the limb manifestation of
a longitudinally extended polar-crown filament channel, and that the
cavity is a region of low density relative to the surrounding corona. As
a first step toward quantifying density and temperature from campaign
spectroscopic data, we establish the three-dimensional morphology
of the cavity. This is critical for taking line-of-sight projection
effects into account, since cavities are not localized in the plane of
the sky and the corona is optically thin. We have augmented a global
coronal streamer model to include a tunnel-like cavity with elliptical
cross-section and a Gaussian variation of height along the tunnel
length. We have developed a semi-automated routine that fits ellipses
to cross-sections of the cavity as it rotates past the solar limb, and
have applied it to Extreme Ultraviolet Imager observations from the
two Solar Terrestrial Relations Observatory spacecraft. This defines
the morphological parameters of our model, from which we reproduce
forward-modeled cavity observables. We find that cavity morphology
and orientation, in combination with the viewpoints of the observing
spacecraft, explain the observed variation in cavity visibility for
the east versus west limbs.
---------------------------------------------------------
Title: Space Based Observations of Coronal Cavities in Conjunction
with the Total Solar Eclipse of July 2010
Authors: Kucera, T. A.; Berger, T. E.; Boerner, P.; Dietzel, M.;
Druckmuller, M.; Gibson, S. E.; Habbal, S. R.; Morgan, H.; Reeves,
K. K.; Schmit, D. J.; Seaton, D. B.
2010AGUFMSH51A1666K Altcode:
In conjunction with the total solar eclipse on July 11, 2010 we
coordinated a campaign between ground and space based observations. Our
specific goal was to augment the ground based measurement of coronal
prominence cavity temperatures made using iron lines in the IR (Habbal
et al. 2010 ApJ 719 1362) with measurements performed by space based
instruments. Included in the campaign were Hinode/EIS, XRT and SOT,
PROBA2/SWAP, SDO/AIA, SOHO/CDS and STEREO/SECCHI/EUVI, in addition
to the ground based IR measurements. We plan to use a combination of
line ratio and forward modeling techniques to investigate the density
and temperature structure of the cavities at that time.
---------------------------------------------------------
Title: Density Diagnostics in Cavities: Incorporating and Bypassing
Projection Effects
Authors: Schmit, D. J.; Gibson, S. E.; Kucera, T. A.
2010AGUFMSH51A1668S Altcode:
The highly ionized corona emits strongly in EUV atomic emission
lines. Comparison of relative emission in various lines provides the
temperature and density of the coronal plasma. We use an Fe XII line
ratio to probe the density of a prominence cavity at heights generally
only accessible to spectroscopic instruments. We take a novel approach
in this diagnostic by fully accounting for the 3D structure of the
corona so as to compensate for the projection effects in optical thin
emission. The density inside the cavity and the streamer are constrained
using a forward model where in emission is synthesized with CHIANTI. The
synthetic emission and scattering is compared to Hinode/EIS and MLSO
MKIV data. A least squares minimization is conducted using a genetic
algorithm. In particular, this work addresses the degree to which we
can answer the question, “Is there a density jump at all heights?”.
---------------------------------------------------------
Title: Flows and Plasma Properties in Quiescent Cavities
Authors: Schmit, Donald; Gibson, Sarah
2009shin.confE.116S Altcode:
Regions of rarefied density often form cavities above quiescent
prominences. In an attempt to constrain the plasma properties of
---------------------------------------------------------
Title: Large-Scale Flows in Prominence Cavities
Authors: Schmit, D. J.; Gibson, S. E.; Tomczyk, S.; Reeves, K. K.;
Sterling, Alphonse C.; Brooks, D. H.; Williams, D. R.; Tripathi, D.
2009ApJ...700L..96S Altcode:
Regions of rarefied density often form cavities above quiescent
prominences. We observed two different cavities with the Coronal
Multichannel Polarimeter on 2005 April 21 and with Hinode/EIS on 2008
November 8. Inside both of these cavities, we find coherent velocity
structures based on spectral Doppler shifts. These flows have speeds of
5-10 km s<SUP>-1</SUP>, occur over length scales of tens of megameters,
and persist for at least 1 hr. Flows in cavities are an example of
the nonstatic nature of quiescent structures in the solar atmosphere.
---------------------------------------------------------
Title: A novel metric for coronal MHD models
Authors: Schmit, D. J.; Gibson, S.; de Toma, G.; Wiltberger, M.;
Hughes, W. J.; Spence, H.; Riley, P.; Linker, J. A.; Mikic, Z.
2009JGRA..114.6101S Altcode: 2009JGRA..11406101S
In the interest of quantitatively assessing the capabilities of
coronal MHD models, we have developed a metric that compares the
structures of the white light corona observed with SOHO LASCO C2
to model predictions. The MAS model is compared to C2 observations
from two Carrington rotations during solar cycle 23, CR1913 and
CR1984, which were near the minimum and maximum of solar activity,
respectively, for three radial heights, 2.5 R<SUB> $\odot$ </SUB>,
3.0 R<SUB> $\odot$ </SUB>, and 4.5 R<SUB> $\odot$ </SUB>. In addition
to simulated polarization brightness images, we create a synthetic
image based on the field topology along the line of sight in the
model. This open-closed brightness is also compared to LASCO C2 after
renormalization. In general, the model's magnetic structure is a
closer match to observed coronal structures than the model's density
structure. This is expected from the simplified energy equations used
in current global corona MHD models.
---------------------------------------------------------
Title: Flows and Plasma Properties in Quiescent Cavities
Authors: Schmit, Donald; Gibson, S.; Reeves, K.; Sterling, A.;
Tomczyk, S.
2009SPD....40.1015S Altcode:
Regions of rarefied density often form cavities above quiescent
prominences. In an attempt to constrain the plasma properties of
"equilibrium" cavities we conduct several diagnostics using Hinode/EIS,
STEREO/EUVI, and CoMP. One novel observation is of large scale flows in
cavities. Using different instruments to observe two distinct cavities
off the solar limb in coronal emission lines, we find that spectral
doppler shifts imply LOS velocities within cavities on the order of
1-10 km/s. These flows occur over length scales of several hundred Mm
and persist for hours.
---------------------------------------------------------
Title: Multi-wavelength Comparison of Prominence Cavities
Authors: Schmit, D. J.; Gibson, S.; de Toma, G.; Reeves, K.; Tripathi,
D.; Kucera, T.; Marque, C.; Tomczyk, S.
2008AGUSMSP43B..04S Altcode:
Recent observational campaigns have brought together a wealth of
data specifically designed to explore the physical properties and
dynamics of prominence cavities. In particular, STEREO and Hinode
data have provided new perspectives on these structures. In order to
effectively analyze the data in a cohesive manner, we produce overlays
of several distinct and complimentary datasets including SOHO UVCS,
CDS, and EIT, Hinode SOT and EIS, STEREO SECCHI, TRACE, and Nancay
Radioheliograph data as well as new observations of coronal magnetic
fields in cavities from the Coronal Multichannel Polarimeter. We are
thus able to investigate how sensitive morphology is to the wavelength
observed which details the nature of the plasma in the cavity.
