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Author name code: munoz-jaramillo
ADS astronomy entries on 2022-09-14
author:Munoz-Jaramillo, Andres
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Title: Comparing the Performance of a Solar Wind model from the Sun
to 1 AU using Real and Synthetic Magnetograms
Authors: Henadhira Arachchige, Kalpa; Cohen, Ofer; Muñoz Jaramillo,
Andrés; Yeates, Anthony R.
2022arXiv220813668H Altcode:
The input of the Solar wind models plays a significant role in
accurate solar wind predictions at 1 AU. This work introduces a
synthetic magnetogram produced from a dynamo model as an input for
Magnetohydrodynamics (MHD) simulations. We perform a quantitative
study that compares the Space Weather Modeling Framework (SWMF) results
for the observed and the synthetic solar magnetogram input. For each
case, we compare the results for Extreme Ultra-Violet (EUV) images and
extract the simulation data along the earth trajectory to compare with
in-situ observations. We initialize SWMF using the real and synthetic
magnetogram for a set of Carrington Rotations (CR)s within the solar
cycle 23 and 24. Our results help quantify the ability of dynamo models
to be used as input to solar wind models and thus, provide predictions
for the solar wind at 1 AU.
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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: A Machine-Learning Oriented Dataset for Forecasting SEP
Occurrence and Properties
Authors: Moreland, Kimberly; Dayeh, Maher A.; Chatterjee, Subhamoy;
Munoz-Jaramillo, Andres; Dayeh, Maher; Bain, Hazel
2022cosp...44.1151M Altcode:
We present a new parameter-rich dataset that is tailored for the
forecasting of solar energetic particle (SEP) events. The dataset
comprises numerous parameters from in situ and remote observatories. It
contains over 18,000 flare events and their associated remote images,
along with their measured X-ray, radio, proton, electron, upstream
interplanetary (IP) plasma, and magnetic field properties. When
available (i.e., positive SEP cases), associated SEP, coronal mass
ejection, and shock properties are provided, in addition to numerous
physics-based derived parameters. In situ data comes from multiple
instruments onboard GOES, ACE, and other 1 au missions. Remote data
comes from instruments on board SDO and SOHO and include full-disc
magnetograms, EUV, and coronagraph images. Selection criteria for
flare event classification and methods for calculating important
SEP properties will be explained. Special consideration is given to
data that is currently available in operational real-time or will be
available in real-time on upcoming missions. The dataset has already
been used in the development of a newly emerging model that forecasts
the occurrence and subsequent properties of SEPs at 1 au.
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Title: Efficient labelling of solar flux evolution videos by a deep
learning model
Authors: Chatterjee, Subhamoy; Muñoz-Jaramillo, Andrés; Lamb,
Derek A.
2022NatAs...6..796C Altcode: 2022NatAs.tmp..143C
Machine learning is becoming a critical tool for the interrogation
of large, complex data. Labelling, defined as the process of adding
meaningful annotations, is a crucial step of supervised machine
learning. However, labelling datasets is time consuming. Here we
show that convolutional neural networks (CNNs) trained on crudely
labelled astronomical videos can be leveraged to improve the quality
of data labelling and reduce the need for human intervention. We
use videos of the solar magnetic field that are divided into two
classes—emergence or non-emergence of bipolar magnetic regions
(BMRs)—on the basis of their first detection on the solar disk. We
train CNNs using crude labels, manually verify, correct disagreements
between the labelling and CNN, and repeat this process until convergence
is reached. Traditionally, flux emergence labelling is done manually. We
find that a high-quality labelled dataset derived through this iterative
process reduces the necessary manual verification by 50%. Furthermore,
by gradually masking the videos and looking for maximum changes in
CNN inference, we locate BMR emergence time without retraining the
CNN. This demonstrates the versatility of CNNs for simplifying the
challenging task of labelling complex dynamic events.
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Title: Revisiting Christoph Scheiner's Sunspot Records: A New
Perspective on Solar Activity of the Early Telescopic Era
Authors: Carrasco, V. M. S.; Muñoz-Jaramillo, A.; Gallego, M. C.;
Vaquero, J. M.
2022ApJ...927..193C Altcode:
Christoph Scheiner was one of the most outstanding astronomers in the
history of sunspot observations. His book, Rosa Ursina, is the reference
work regarding the study of the earliest sunspot records. The sunspot
observations compiled by Scheiner in Rosa Ursina and Prodomus, including
records made by other observers, forms one of the main references
of the observations known for that period-particularly around the
1620s. Thus, his work is crucial to determine the solar activity level
of the first solar cycles of the telescopic era. The number of sunspot
groups recorded in Scheiner's documentary sources has been included
in the existing sunspot group number databases. However, we have
detected significant errors in the number of groups currently assigned
to Scheiner's records. In this work, we reanalyze the information in
Scheiner's source documents. Consequently, the standard 11 yr solar
cycle shape for the second solar cycle of the telescopic era, which is
not clear in previous studies, now becomes evident. In addition, the
highest daily number of groups recorded during this cycle (eight groups)
is 20% less than in the one included in the existing sunspot group
number databases. Using the hypergeometrical probability distribution,
we find that solar minima in 2008-2009 and 2018-2019 are comparable to
the most probable solar activity level of the minimum around 1632. In
particular, the estimated lower limit for the solar activity in 1632
is even comparable with the solar activity level in 2008 and 2018.
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Title: Deep-SWIM: A few-shot learning approach to classify Solar
WInd Magnetic field structures
Authors: Lamdouar, Hala; Sundaresan, Sairam; Jungbluth, Anna; Boro
Saikia, Sudeshna; Camarata, Amanda Joy; Miles, Nathan; Scoczynski,
Marcella; Stone, Mavis; Sarah, Anthony; Muñoz-Jaramillo, Andrés;
Narock, Ayris; Szabo, Adam
2022arXiv220301184L Altcode:
The solar wind consists of charged particles ejected from the Sun into
interplanetary space and towards Earth. Understanding the magnetic field
of the solar wind is crucial for predicting future space weather and
planetary atmospheric loss. Compared to large-scale magnetic events,
smaller-scale structures like magnetic discontinuities are hard
to detect but entail important information on the evolution of the
solar wind. A lack of labeled data makes an automated detection of
these discontinuities challenging. We propose Deep-SWIM, an approach
leveraging advances in contrastive learning, pseudo-labeling and
online hard example mining to robustly identify discontinuities in
solar wind magnetic field data. Through a systematic ablation study,
we show that we can accurately classify discontinuities despite
learning from only limited labeled data. Additionally, we show that
our approach generalizes well and produces results that agree with
expert hand-labeling.
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Title: VizieR Online Data Catalog: SCO daily sunspot area measurements
(1886-1940) (Carrasco+, 2021)
Authors: Carrasco, V. M. S.; Munoz-Jaramillo, A.; Nogales, J. M.;
Gallego, M. C.; Vaquero, J. M.
2022yCat..22560038C Altcode:
The yearbooks published by the Stonyhurst
College Observatory (SCO) are available online:
http://www.geomag.bgs.ac.uk/data_service/data/yearbooks/sto.html See
Section 2. <P />Fortunately, we know some details of the instruments
used in these solar observations. An 8 inch (around 0.2m) refractor
telescope was used to observe sunspots until 1893 (Stonyhurst College
Observatory 1892). In 1893, that telescope was dismounted and replaced
by a new 15-inch (~0.4m) refractor. In 1893, while the installation
of the new telescope was finished, the sunspot drawings were carried
out with a 6-inch (~0.15m) refractor. Moreover, the observatory also
had another 7-inch Newtonian refractor and a 9 1/2 inch altazimuth
reflector. In order to carry out the sunspot drawings, the observers
at SCO put a light board at the eye end of the telescope and made
the drawing from the projected image (Stonyhurst College Observatory
1881). The diameter of the projected image was 10.5 inches (~0.26m). In
the case of sunspots with special interest, an enlarged drawing was
made on a scale of 30 inches (~0.76m) to the solar diameter. <P />(2
data files).
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Title: Large Scale Collaborative Science: Lessons Learned from the
Phase I COFFIES DRIVE Science Center
Authors: Hess Webber, Shea; Upton, Lisa; Munoz-Jaramillo, Andres;
Hoeksema, J.; Bush, Rock; Lauben, Dave
2021AGUFMSH55D1863H Altcode:
The National Research Council published a report on Enhancing the
Effectiveness of Team Science in 2015. This report identified 7
fundamental challenges that large research teams, such as the
NASA DRIVE Science Centers (DSC), might face including: high
diversity of membership, deep knowledge integration, large size,
goal misalignment, permeable boundaries, geographic dispersion,
and high task interdependence. In Phase I, the COFFIES DSC formed
a Center Effectiveness Team (CET) to identify and help overcome
these and other unique challenges, including those introduced by the
COVID-19 pandemic. CET members have focused on finding and exploring
novel ways to align and direct the Science Teams with the goal of
enabling breakthrough science. We will present the CET initiatives and
implementations, and review the lessons learned for future large-scale
science collaborations.
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Title: Comparing the Performance of a Solar Wind model from the Sun
to 1 AU using Real and Synthetic Magnetograms
Authors: Henadhira Arachchige, Kalpa; Cohen, Ofer; Munoz-Jaramillo,
Andres
2021AGUFMSH55C1846H Altcode:
We perform a quantitative study which compares the results of the Alfven
Wave Solar Atmosphere Model (AWSoM) within the Space Weather Modeling
Framework (SWMF). For selected Carrington Rotations, we drive the model
by two different solar magnetogram inputs, the observed magnetogram,
and a synthetic magnetogram produced by a dynamo model. We simulate the
Solar Corona (SC) and the Inner Heliosphere (IH) domains using these
SWMF modules. For each case, we compare the observed and simulated
cases (real and synthetic magnetogram) using the model synthesized
multi-wavelength EUV images. We also extract the simulation data
from the IH domain along the earth trajectory to compare with OMNI
observational data at 1 au. We initialize the model using the synoptic
magnetogram (real magnetogram) and the surface fields maps produced
by the dynamo model (synthetic magnetogram) for a set of Carrington
rotations within the solar cycle 23 and 24. Our results help to quantify
the ability of dynamo models to be used as input to solar wind models,
and thus, provide predictions for the solar wind at 1AU.
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Title: Impact of Anomalous Active Regions on the Large Scale Magnetic
Fields of the Solar Cycle
Authors: Pal, Shaonwita; Nandy, Dibyendu; Bhowmik, Prantika; Dash,
Soumyaranjan; Mahajan, Sushant; Munoz-Jaramillo, Andres
2021AGUFMSH55D1878P Altcode:
Emergence of anomalous bipolar magnetic regions (combinations of
anti-hale and anti-joy regions) on the solar surface can influence cycle
to cycle variability and irregularities. We perform a comprehensive
analysis of the dipole moment and polar field build up due to
the appearance of anomalous active regions on the solar surface
using a solar surface flux transport model. Our aim is to study the
differences and the similarities between these anomalous regions and
their effect in global solar cycle dynamics. Although these regions
appear in small numbers, if they carry significant flux, they are
found to significantly impact the polar field strength and thereby,
the amplitude of future cycles.
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Title: Leveraging a Deep Neural Network to Efficiently Label Solar
Flux Emergence Videos
Authors: Chatterjee, Subhamoy; Munoz-Jaramillo, Andres; Lamb, Derek
2021AGUFMNG45B0557C Altcode:
Machine learning is becoming a critical tool for interrogation of large
complex data. However, labeling large datasets is time consuming. Here
we show that convolutional neural networks (CNNs), trained on crudely
labeled astronomical videos, can be leveraged to improve the quality
of data labeling and reduce the need for human intervention. We use
videos of the solar photospheric magnetic field, crudely labeled into
two classes: emergence or non-emergence of large bipolar magnetic
regions (BMRs) that have have the potential to drive space weather
events. We train the CNN using crude labeling, manually verify,
correct labeling vs. CNN disagreements, and repeat this process until
convergence. This results in a high-quality labeled dataset requiring
the manual verification of only ~50% of all videos. Furthermore,
by gradually masking the videos and looking for maximum change in
CNN inference, we locate BMR emergence time without retraining the
CNN. This demonstrates the versatility of CNNs for simplifying the
challenging task of labeling complex dynamic events.
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Title: Increasing reliability of Solar Energetic Particle forecast
through calibration of neural network outcome
Authors: Chatterjee, Subhamoy; Munoz-Jaramillo, Andres; Bain, Hazel;
Moreland, Kimberly Dianne; Dayeh, Maher
2021AGUFMSM51B..04C Altcode:
Solar Energetic Particles (SEPs) are among the crucial drivers of
space weather in the near-Earth environment. Thus reliable forecast
of SEPs is of immense value.We built a deep learning (DL) model to
predict SEPs utilizing a rich remote sensing and in-situ database
that is being discussed elsewhere in the meeting. Generally the
probabilistic outcomes produced by such models do not correlate well
with the observed frequency of events and thus lack in reliability to
be used with confidence for real-time forecast as operational mode. We
use a temperature scaling approach on a hold-out set to calibrate
the probabilistic outcome of our trained DL model. We finally apply
our calibrated model on a test-set and show that the calibration
significantly improves the model reliability i.e. SEP probability
matches SEP frequency much better across the probability bins.
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Title: Classification of Solar Wind Structures via Unsupervised
Machine Learning
Authors: Stone, Mavis; Camarata, Amanda; Jungbluth, Anna;
Munoz-Jaramillo, Andres; Lamdouar, Hala; Martins, Marcella; Miles,
Nathan; Saikia, Sudeshna; Sundaresan, Sairam; Sarah, Anthony
2021AGUFMNG45B0572S Altcode:
The solar wind is a constant stream of plasma structured by the solar
magnetic field that is radially ejected from our Sun to the boundaries
of our solar system. Organizations such as NASA and ESA have gathered
nearly half a century of data on solar wind, but much of it has yet
to be analyzed for improved understanding on solar wind evolution. So
far, heliophysicists have primarily focused on understanding specific
structures such as interplanetary coronal mass ejections and large-scale
discontinuities; however, there exist many statistically significant
structures that have yet to be discovered. In this work, we create a
new, unsupervised framework designed to catalog both known and unknown
structures using magnetic field time series data from the three-year-old
Parker Solar Probe. We combine iSAX indexing and HDB Scan clustering
to identify, retrieve, and cluster similar magnetic field structures,
a challenge that would otherwise be impossible. More specifically,
we perform preliminary clustering on similar solar wind structures
with 0.005% of the operations traditional clustering would normally
require. Our method can be used on other time series data including,
but not limited to: plasma velocity, density, and electron composition,
all of which can offer further insight into space weather and its impact
on Earth and our satellites. Additionally, the great size, detail, and
level of organization of our catalog can expedite efforts to learn more
about the origins and evolution of the solar wind. Beyond the scope of
our work, this easily reproducible framework can be applied to other
fields of research aiming to analyze large amounts of time series data.
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Title: Sunspot Catalog (1921-1935) and Area Series (1886-1940)
from the Stonyhurst College Observatory
Authors: Carrasco, V. M. S.; Muñoz-Jaramillo, A.; Nogales, J. M.;
Gallego, M. C.; Vaquero, J. M.
2021ApJS..256...38C Altcode:
A sunspot observation program was started at the end of the 19th century
at the Stonyhurst College Observatory (hereafter SCO) by Father Perry,
director of the observatory at that time. A digitization of the daily
sunspot area series recorded in this observatory from 1886 to 1940
(with a gap between 1889 and 1897) is provided in this work. This
depicts one of the oldest sunspot area series available. A comparison
of this series with contemporary area series made in other observatories
shows that SCO generally recorded larger areas than those in some of the
observatories of that time such as, for example, the Royal Greenwich
Observatory (RGO). Furthermore, SCO published a sunspot group catalog
for the period 1921-1935. We provide a machine-readable version of this
catalog. We compared the SCO group number series with other sunspot
data obtained from other observatories. In this case, for example, the
RGO systematically recorded more groups than the SCO. We compared SCO
and RGO area distribution functions obtaining the calibration constant
between both data sets. We also obtained the butterfly diagram from the
group latitudes recorded by SCO and compared the percentages of group
types computed from the SCO catalog with those from Valencia Observatory
(following the Cortie morphological classification of sunspot groups),
identifying their similarities and differences.
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Title: Solar Anti-Hale Bipolar Magnetic Regions: A Distinct Population
with Systematic Properties
Authors: Muñoz-Jaramillo, Andrés; Navarrete, Benjamín; Campusano,
Luis E.
2021ApJ...920...31M Altcode: 2022arXiv220311898M
Besides their causal connection with long and short-term magnetic
variability, solar bipolar magnetic regions are our chief source of
insight into the location, size, and properties of large-scale toroidal
magnetic structures in the solar interior. The great majority of these
regions (≍95%) follow a systematic east-west polarity orientation
(Hale's law) that reverses in opposite hemispheres and across even and
odd cycles. These regions also present a systematic north-south polarity
orientation (Joy's law) that helps build the poloidal field that seeds
the new cycle. Exceptions to Hale's law are rare and difficult to study
due to their low numbers. Here, we present a statistical analysis of the
inclination (tilt) with respect to the equator of Hale versus anti-Hale
regions spanning four solar cycles, considering two complementary
tilt definitions adopted in previous studies. Our results show that
anti-Hale regions belong to a separate population than Hale regions,
suggesting a different originating mechanism. However, we find that
anti-Hale region tilts present similar systematic tilt properties
and similar latitudinal distributions to Hale regions, implying a
strong connection between the two. We see this as evidence that they
belong to a common toroidal flux system. We speculate that anti-Hale
regions originate from poloidal field sheared and strengthened on the
spot after the emergence of Hale regions with very strong poloidal
contribution. Thus, they are not in contradiction with the idea of
largely coherent toroidal flux systems inside the solar interior.
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Title: Improved Measurements of the Sun's Meridional Flow and
Torsional Oscillation from Correlation Tracking on MDI and HMI
Magnetograms
Authors: Mahajan, Sushant S.; Hathaway, David H.; Muñoz-Jaramillo,
Andrés; Martens, Petrus C.
2021ApJ...917..100M Altcode: 2021arXiv210707731M
The Sun's axisymmetric flows, differential rotation, and meridional
flow govern the dynamics of the solar magnetic cycle, and a variety of
methods are used to measure these flows, each with its own strengths
and weaknesses. Flow measurements based on cross-correlating images of
the surface magnetic field have been made since the 1970s that require
advanced numerical techniques that are capable of detecting movements
of less than the pixel size in images of the Sun. We have identified
several systematic errors in addition to the center-to-limb effect that
influence previous measurements of these flows and propose numerical
techniques that can minimize these errors by utilizing measurements
of displacements at several time lags. Our analysis of line-of-sight
magnetograms from the Michelson Doppler Imager on the ESA/NASA Solar
and Heliospheric Observatory and the Helioseismic and Magnetic Imager
on the NASA Solar Dynamics Observatory shows long-term variations in
the meridional flow and differential rotation over two sunspot cycles
from 1996 to 2020. These improved measurements can serve as vital
inputs for solar dynamo and surface flux transport simulations.
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Title: Leveraging a Deep Neural Network to Efficiently Label Solar
Flux Emergence Videos
Authors: Chatterjee, S.; Munoz-Jaramillo, A.; Lamb, D.
2021AAS...23812302C Altcode:
Machine learning can be an efficient approach to discover patterns
from large datasets. Supervised learning techniques often surpass
unsupervised approaches for performing classification tasks on complex
data. However, labeling large datasets is a time consuming process. In
this study, we show that a convolutional neural network(CNN), trained on
crudely labeled time sequences of astronomical images, can be leveraged
to improve the quality of datalabeling in a time efficient manner that
minimizes human intervention. Furthermore, a CNN trained to determine
if an event takes place within the image sequence can be re-purposed,
without changes, to determine the time of the event occurrence.We
use SoHO/MDI videos of the solar photospheric magnetic, approximately
labeled into two classes: emergence or non-emergenceof large bipolar
magnetic regions. The complex interaction of solar magnetic elements
often limits the ability of conventional image-processing techniques to
identify this emergence, especially near the solar limb. Our results
demonstrate that big datasets do not need to be perfectly labeled for
supervised learning. Instead, focusing only on false model inferences
can refine labeling. We also test the limits of the detection ability
of our network by resampling the data both spatially and temporally
to simulate other instruments.
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Title: Cross-calibration, super-resolution, and uncertainty estimation
of the conversion of MDI and GONG to HMI full-disk magnetograms
using deep learning
Authors: Munoz-Jaramillo, A.; Jungbluth, A.; Gitiaux, X.; Wright,
P.; Shneider, C.; Maloney, S.; Kalaitzis, A.; Baydin, A.; Gal, Y.;
Deudon, M.
2021AAS...23812303M Altcode:
Over the past 50 years, a variety of instruments have obtained images
of the Sun's magnetic field (magnetograms) to study its origin
and evolution. While improvements in instrumentation have led to
breakthroughs in our understanding of physical phenomena, differences
between subsequent instruments such as resolution, noise, and saturation
levels all introduce inhomogeneities into long-term data sets. This
has proven to be an insurmountable obstacle for research applications
that require high-resolution and homogeneous data spanning time frames
longer than the lifetime of a single instrument. <P />Here we show
that deep-learning-based super-resolution techniques can successfully
up-sample and homogenize solar magnetic field images obtained both by
space and ground-based instruments. In particular, we show the results
of cross-calibrating and super-resolving MDI and GONG magnetograms
to the characteristics of HMI. <P />We also discuss the importance
of agreeing on a standardized set of training, validation, and test
data, as well as metrics that enable the community to benchmark
different approaches to collectively and quantitatively identify
the best practices. This includes distributing test data within the
broad heliophysics community. <P />Finally, we discuss our approach
for making an empirical estimation of uncertainty and the importance
that uncertainty estimation plays in the credibility and usefulness
of deep learning applications in heliophysics.
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Title: Investigating the Polar Flux Budget with the Advective Flux
Transport Model
Authors: Upton, L.; Munoz-Jaramillo, A.
2021AAS...23832805U Altcode:
The strength of the magnetic field at the Sun's poles near the time of
a sunspot cycle minimum is a crucial component to the solar dynamo and
is thought to determine the strength of the following solar activity
cycle. Unfortunately, our knowledge of the polar magnetic field
is limited to what can be gleaned from measurements taken from the
ecliptic on the Sun-Earth line; a vantage point from which the dynamics
of polar field evolution are not easily observable. Many surface flux
transport models use a loss term, thought to represent the subduction
of magnetic flux to the interior, in order to accurately reproduce the
evolution of the polar fields. Others include the emergence of ephemeral
active regions in the polar regions. We use the realistic Advective Flux
Transport (AFT) model, in combination with HMI observations, to simulate
the evolution of the Sun's polar magnetic fields for three different
scenarios: pure flux transport, flux transport with subduction, and
flux transport with ephemeral emergence. We show the impact of these
different scenarios on the polar flux budget and discuss the advantages
that a polar viewpoint, like that of the SOLARIS mission, will provide
for measuring and understanding polar magnetic field evolution.
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Title: Deciphering the Deep Origin of Active Regions via Analysis
of Magnetograms
Authors: Dikpati, Mausumi; McIntosh, Scott W.; Chatterjee, Subhamoy;
Norton, Aimee A.; Ambroz, Pavel; Gilman, Peter A.; Jain, Kiran;
Munoz-Jaramillo, Andres
2021ApJ...910...91D Altcode:
In this work, we derive magnetic toroids from surface magnetograms
by employing a novel optimization method, based on the trust region
reflective algorithm. The toroids obtained in this way are combinations
of Fourier modes (amplitudes and phases) with low longitudinal
wavenumbers. The optimization also estimates the latitudinal width of
the toroids. We validate the method using synthetic data, generated
as random numbers along a specified toroid. We compute the shapes and
latitudinal widths of the toroids via magnetograms, generally requiring
several m's to minimize residuals. A threshold field strength is
chosen to include all active regions in the magnetograms for toroid
derivation, while avoiding non-contributing weaker fields. Higher
thresholds yield narrower toroids, with an m = 1 dominant pattern. We
determine the spatiotemporal evolution of toroids by optimally weighting
the amplitudes and phases of each Fourier mode for a sequence of five
Carrington Rotations (CRs) to achieve the best amplitude and phases for
the middle CR in the sequence. Taking more than five causes "smearing"
or degradation of the toroid structure. While this method applies no
matter the depth at which the toroids actually reside inside the Sun,
by comparing their global shape and width with analogous patterns
derived from magnetohydrodynamic (MHD) tachocline shallow water model
simulations, we infer that their origin is at/near the convection zone
base. By analyzing the "Halloween" storms as an example, we describe
features of toroids that may have caused the series of space weather
events in 2003 October-November. Calculations of toroids for several
sunspot cycles will enable us to find similarities/differences in
toroids for different major space weather events.
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Title: The Language of Stars
Authors: Berea, A.; Munoz-Jaramillo, A.
2021BAAS...53c1144B Altcode:
NASA Frontier Development Lab (FDL) is a research accelerator that
brings together data scientists and space scientists to solve some
of the most difficult space and planetary problems using AI. This
project is a spin-off of one of the main challenges, that identified
star spots in Kepler data. But in this spin-off project we are looking
at applications of specific AI techniques (natural language processing
— NLP) to time series (light curves) in order to identify both unique
features and patterns in time series in general, and in light curves in
particular. We both construct and derive informational building blocks
that are characteristic to the light curves of the stars in a subset of
Kepler data and we compare these methods to more traditional machine
learning applications (clustering). We show how this new methodology,
rooted in NLP, can be a good alternative for the analysis of light
curves and potentially for identifying exoplanetary transit as unique
"linguistic" features. <P />The idea for this project came from asking
the following questions, one pertaining to advancing a potentially
new methodology in machine learning, and another one pertaining to
astrophysics: <P />1. Can we use NLP to discover features in time
series? if yes, how good is it comparatively to other methods, such as
clustering? <P />2. Can we create a "dictionary" of star features that
we can use as a genetic code to catalogue and identify any star, and
that we can also use to simulate stars that we have not yet observed? <P
/>Starting with these questions, we embarked on an exploratory research,
to understand whether a duo of a combination of ML methods and an
application to star light curves can help us discover features and
patterns within time series, in general, and within light curves,
in particular. The rationale or the big WHY of such methodological
& science specific exploration stems from a few facts that we
tried to connect coherently: NLP is good at discovering patterns in
messy/noisy, unstructured data (such as languages); NLP is great for
creating vocabularies, dictionaries, taxonomies; NLP is also good at
creating new and large texts (data) from small lists of dictionaries
and vocabularies. Based on these assumptions, our first methodological
challenge came from trying to understand the best method or algorithm
to create textual data (for our NLP goals) from numeric data (from
our given time series). In other words, the first step was to create
the "words", "letters" or the "n-grams" from light curves data. For
this proof of concept, we used 632 original Kepler light curves,
with the idea to scale it up to analyze and parse more than 110K
light curves, data available during the FDL program (summer 2020);
if this proves successful, we aim to afterwards add TESS light curve
data as well. The light curve data we used therefore consists of 632
time series, collected over a period of about 4 years on a cadence of
every 20 minutes. <P />We used 6 different methodologies to create
6 different corpora from the entire dataset — each corpus is a
collection of 632 individual "books", where each book/light curve
is a sequence of n-grams that we created based on these methods:
<P />1.1. Bin-based (large) — we binned the data in bins of 10 (1
order of magnitude), and for each bin we assigned a "binXX" n-gram;
<P />1.2. Bin-based (small) — we binned the data in bins of 100 (2
orders of magnitude), and for each bin we assigned a "binXXX" n-gram;
<P />1.3. Peaks and troughs — for each sequence of consecutive peaks
and trough in the time series, we assigned "posXX" or "negXX" n-gram,
where "pos" stands for the peak in the time series, "neg" stands for
the trough in the time series, and XX is the number of consecutive
peaks or troughs observed in the data; <P />1.4. PD clustering-based
— this method is based on measurements of entropy and complexity in
the time series; <P />1.5. Zipf distribution-based — in this method,
we fitted a Zipf distribution to each star light curve and created the
n-grams based on the rank of the frequency of the data given by the
distribution. The Zipf Law is one of the most important laws observed in
human languages, but also in physical phenomena such as earthquakes, and
is scale invariant, a very important property for pattern detection in
a wide range of scales; <P />1.6. 3-movement-based — in this method,
we partitioned the data into 6 types of movements of any 3 consecutive
data points in the light curves. <P />Entropy measurements. A first
observation from our analyses has been that methods 1.1 and 1.2 show
the Shannon entropy of the n-grams is the closest to the Shannon
entropy of the light curves, and can be interpreted as the method
that closest preserves the information from the light curve through
the text transformation. Shannon entropy is one of the most important
measures of information in natural language processing. <P />PRELIMINARY
RESULTS. Clustering. We tried many clustering methods on the actual
data, in order to extract features that we would a posteriori use
for n-gram creation (i.e., unsupervised k-means clustering, knn,
hierarchical, etc.). Out of all the tried clustering methods, the one
that is also based on entropy and which we used in our n-gram method
1.4, PD clustering, shows the most promising results in isolating
specific features within the light curves. We also clustered based on
the difference time series, and the difference isolates even better
specific features in the light curves. <P />Topic Modeling. After
creating the n-grams, we performed topic modeling (TM), an NLP specific
method, that is grouping the n-grams within a corpus based on their
probability of occurrence within a star. The TM method showed us which
star features are most likely to occur next to each other across all
632 light curves.
---------------------------------------------------------
Title: The Language of Stars
Authors: Berea, Anamaria; Munoz-Jaramillo, Andres
2021cosp...43E.533B Altcode:
NASA Frontier Development Lab (FDL) is a research accelerator that
brings together data scientists and space scientists to solve some of
the most difficult space and planetary problems using AI. This project
is a spin-off of one of the main challenges, that identified star
spots in Kepler data. But in this spin-off project we are looking at
applications of specific AI techniques (natural language processing -
NLP) to time series (light curves) in order to identify both unique
features and patterns in time series in general, and in light curves in
particular. We both construct and derive informational building blocks
that are characteristic to the light curves of the stars in a subset of
Kepler data and we compare these methods to more traditional machine
learning applications (clustering). We show how this new methodology,
rooted in NLP, can be a good alternative for the analysis of light
curves and potentially for identifying exoplanetary transit as unique
"linguistic" features.
---------------------------------------------------------
Title: Super-resolution of Solar Magnetograms
Authors: Wright, P. J.; Gitiaux, X.; Jungbluth, A.; Maloney, S.;
Shneider, C.; Kalaitzis, A.; Baydin, A. G.; Deudon, M.; Gal, Y.;
Munoz-Jaramillo, A.
2020AGUFMSH0440001W Altcode:
Over the past 50 years, a variety of instruments have obtained
images of the Sun's magnetic field (magnetograms) to study its
origin and evolution. While improvements in instrumentation have
led to breakthroughs in our understanding of physical phenomena,
differences between subsequent instruments such as resolution, noise,
and saturation levels all introduce inhomogeneities into long-term data
sets. This poses a significant issue for research applications that
require high-resolution and homogeneous data spanning time frames longer
than the lifetime of a single instrument. <P />As super-resolution is
an ill-posed problem, multiple super-resolution outputs can explain a
low-resolution input. Classical methods, such as bicubic upsampling,
use only the information contained in the low-resolution image. However,
in recent years it has been shown that a learning-based approach can
constrain the non-trivial solution space by exploiting regularities
within a specific distribution of images. <P />In this work, we
cross-calibrate and super-resolve magnetic field data obtained by the
Michelson Doppler Imager (MDI; 1024 x 1024 px) and the Helioseismic and
Magnetic Imager (HMI; 4096 x 4096 px). These instruments overlap from
2010 to 2011, resulting in approximately 9000 co-temporal observations
of the same physical structures. Our deep learning model is trained on a
subset of the overlapping data after initial pre-processing to correct
for temporal and orbital differences between the instruments. <P />We
evaluate the quality of the predictive output of the model with a series
of performance metrics. These metrics include the distribution of the
magnetic field and physical properties captured by the signed/unsigned
field. Our approach also needs to quantify the certainty of predictions
to be valuable to scientists. To address this, we estimate the posterior
distribution of the super-resolved magnetic field by introducing Monte
Carlo dropouts on each convolutional layer.
---------------------------------------------------------
Title: Derivation of Toroid Patterns from Analysis of Magnetograms
And Inferring Their Deep-origin
Authors: Chatterjee, S.; Dikpati, M.; McIntosh, S. W.; Norton, A. A.;
Ambroz, P.; Gilman, P.; Jain, K.; Munoz-Jaramillo, A.
2020AGUFMSH0020013C Altcode:
We employ a novel optimization method based on Trust Region Reflective
algorithm to derive magnetic toroids from surface magnetograms. Toroids
obtained are combinations of Fourier modes (amplitudes and phases)
with low longitudinal wavenumbers. After validating the method using
synthetic data generated as random numbers along a specified toroid,
we compute shapes and latitudinal-widths of toroids from magnetograms,
usually requiring several m 's to minimize residuals. By comparing
properties of these toroids with patterns produced in the bottom
toroidal band undergoing MHD evolution in a 3D thin-shell shallow-water
type model, we infer their deep origin at/near convention-zone's base
or tachocline. A threshold field-strength is chosen to include all
active regions in magnetograms for toroid derivation, while avoiding
non-contributing weaker fields. Higher thresholds yield narrower
toroids, with m = 1 dominant, implying that stronger active regions
are erupting from the core of the toroids at bottom. We determine the
spatio-temporal evolution of toroids by optimally weighting amplitudes
and phases of each Fourier mode for a sequence of 5 Carrington Rotations
(CRs) to get the best amplitude and phases for the middle CR in the
sequence. Taking more than 5 causes 'smearing' or degradation of toroid
structure. As an example case, we analyze 'Halloween' storms toroids,
and describe the features that might have caused the series of space
weather events in October-November of 2003. We compare features of
these toroids with analogous patterns derived from model-output. To find
similarities/differences in toroids for different major space weather
events, we will analyze long-term magnetograms for several solar cycles.
---------------------------------------------------------
Title: RotNet: Fast and Scalable Estimation of Stellar Rotation
Periods Using Convolutional Neural Networks
Authors: Johnson, J. Emmanuel; Sundaresan, Sairam; Daylan, Tansu;
Gavilan, Lisseth; Giles, Daniel K.; Ishitani Silva, Stela; Jungbluth,
Anna; Morris, Brett; Muñoz-Jaramillo, Andrés
2020arXiv201201985J Altcode:
Magnetic activity in stars manifests as dark spots on their surfaces
that modulate the brightness observed by telescopes. These light
curves contain important information on stellar rotation. However, the
accurate estimation of rotation periods is computationally expensive
due to scarce ground truth information, noisy data, and large parameter
spaces that lead to degenerate solutions. We harness the power of deep
learning and successfully apply Convolutional Neural Networks to regress
stellar rotation periods from Kepler light curves. Geometry-preserving
time-series to image transformations of the light curves serve as
inputs to a ResNet-18 based architecture which is trained through
transfer learning. The McQuillan catalog of published rotation periods
is used as ansatz to groundtruth. We benchmark the performance of
our method against a random forest regressor, a 1D CNN, and the
Auto-Correlation Function (ACF) - the current standard to estimate
rotation periods. Despite limiting our input to fewer data points (1k),
our model yields more accurate results and runs 350 times faster than
ACF runs on the same number of data points and 10,000 times faster than
ACF runs on 65k data points. With only minimal feature engineering
our approach has impressive accuracy, motivating the application of
deep learning to regress stellar parameters on an even larger scale
---------------------------------------------------------
Title: Erratum: "A Machine-learning Data Set Prepared from the NASA
Solar Dynamics Observatory Mission" (2019, ApJS, 242, 7)
Authors: Galvez, Richard; Fouhey, David F.; Jin, Meng; Szenicer,
Alexandre; Muñoz-Jaramillo, Andrés; Cheung, Mark C. M.; Wright,
Paul J.; Bobra, Monica G.; Liu, Yang; Mason, James; Thomas, Rajat
2020ApJS..250...38G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Using Deep Learning to Produce a Labelled Solar Flux Emergence
Data-set
Authors: Chatterjee, S.; Munoz-Jaramillo, A.; Lamb, D.
2020SPD....5120703C Altcode:
With the advent of space-based observatories, we are facing a big data
problem in astronomy. Machine learning serves as an efficient approach
to discover patterns from such data. Supervised learning techniques
(e.g. neural networks) often surpass unsupervised approaches for
performing classification tasks on complex data. However, labeling
large datasets is an onerous and time-consuming process that is often
prohibitively expensive. In this study, we show that a deep neural
network trained on crudely labeled astronomical data can be leveraged
to improve the quality of data labeling in a time efficient manner
that minimizes human intervention. We use SoHO/MDI magnetic evolution
videos, approximately labeled for emergence/non-emergence. We train a
convolutional neural network (CNN) to perform the classification task
and only manually verify the labels of videos, which are incorrectly
classified by the model. We iterate this process until there is no
change in classification accuracy. After performing a full manual
verification, we find that the large majority of videos where the model
succeeded were indeed properly labeled. We also show that apart from
performing the classification task, the model is able to identify when
emergence occurs. Our results demonstrate that big datasets do not need
to be perfectly labeled initially for supervised learning. Instead,
focusing only on failed examples can refine the labeling. This subset
is by definition smaller than the full set and thus requires less
manual work. Solar magnetic flux-emergence is often associated with
space weather events that can potentially have a disruptive impact on
long-distance communications. The complex interaction of solar magnetic
elements often limits the ability of conventional image-processing
techniques to identify flux emergence. Our CNN's ability to identify
both the emergence event and its starting time hints at the possibility
of using deep learning to enable flux emergence prediction.
---------------------------------------------------------
Title: Validating and Cross-Calibrating Long-term Solar Cycle Data
for Driving Solar Cycle Models
Authors: Munoz-Jaramillo, A.; Vaquero, J. M.
2019AGUFMSM31C3550M Altcode:
The Sun is the main driver of variability in the interplanetary
environment and Earth's upper atmosphere. This influence is felt across
a multiplicity of spatial and temporal scales ranging from seconds
to decades. Long-term variability requires homogeneous observational
surveys covering long periods of time, which are incompatible with
modern funding cycles and are seriously undervalued by governmental
agencies, especially in the United States. For this reason, it is often
necessary to piece multiple heterogeneous instruments and surveys with
different experimental design, characteristics, and systematics. Here
we discuss an array of historical data sets (magnetic, optical and in
the form of reduced time series) that give us direct insight on the
long-term evolution of solar activity and the efforts that are being
made to piece them together into homogenous composites that can be
used to constrain and drive models of solar activity. We highlight the
importance of ensuring that historical surveys are properly preserved
and modernized for future generations, and discuss important aspects
of documenting them so that future users can take better advantage of
the insight they provide.
---------------------------------------------------------
Title: International Scientific Coordination on Space Weather:
A COSPAR Panel on Space Weather Perspective
Authors: Kuznetsova, M.; Bisi, M. M.; Kusano, K.; Fuller-Rowell,
T. J.; Mann, I.; Belehaki, A.; Minow, J. I.; Munoz-Jaramillo, A.;
Masson, A.; Bruinsma, S.; Bisi, M. M.; Kuznetsova, M. M.; Temmer, M.;
Opgenoorth, H. J.; Belehaki, A.; Bruinsma, S.; Glover, A.; Heynderickx,
D.; Linker, J.; Mann, I. R.; Murray, S. A.; Nandy, D.
2019AGUFMSM31C3543K Altcode:
The understanding and prediction of space-weather phenomena and
their respective impact(s) on society have been widely-acknowledged
as an international challenge and something that requires a global
coordination and focus. In order to address this need to form
more-formal worldwide collaboration and coordination, and to maximise
return on such efforts (particularly scientifically), the Committee
on Space Research (COSPAR) Panel on Space Weather (PSW) has created a
network of International Space Weather Action Teams (ISWATs). <P />The
COSPAR PSW ISWAT initiative is capitalising on established efforts by
engaging existing national and international "teams" and "facilitates"
to form individual ISWATs that are being grouped into clusters
by domains/themes related to different aspects of solar/coronal,
heliospheric, ionospheric/atmospheric, and planetary space-weather
phenomena. The initiative also includes overarching themes such as
dealing with large data sets and model/scientific validations. The
ISWAT initiative places a strong encouragement for scientists to go
beyond their funding borders to form ISWATs better suited to address
challenges that one individual or small group/team may not be able to
address alone. <P />The ISWAT initiative serves as a global hub for
community coordinated topical focused collaborations and as a global
community voice for the next generation of both scientific and strategic
planning - this includes an update of the COSPAR/ILWS space weather
scientific roadmap (to transform the roadmap into a living document)
and to potentially provide an operational roadmap in parallel. <P
/>This presentation will re-introduce the ISWAT initiative, review
its current status and plans for community-wide campaigns, highlight
the overarching current plans for PSW, and place a focus on two key
space-weather areas: the ambient heliosphere/background solar wind
(designated as ISWAT theme H1) and CME structure, evolution and
propagation through heliosphere (designated as ISWAT theme H2).
---------------------------------------------------------
Title: Visualization of the challenges and limitations of the
long-term sunspot number record
Authors: Muñoz-Jaramillo, Andrés; Vaquero, José M.
2019NatAs...3..205M Altcode: 2018NatAs...3..205M; 2022arXiv220311919M
The solar cycle periodically reshapes the magnetic structure
and radiative output of the Sun and determines its impact on the
heliosphere roughly every 11 years. Besides this main periodicity,
it shows century-long variations (including periods of abnormally low
solar activity called grand minima). The Maunder Minimum (1645-1715) has
generated significant interest as the archetype of a grand minimum in
magnetic activity for the Sun and other stars, suggesting a potential
link between the Sun and changes in terrestrial climate. Recent
reanalyses of sunspot observations have yielded a conflicted view on
the evolution of solar activity during the past 400 years (a steady
increase versus a constant level). This has ignited a concerted
community-wide effort to understand the depth of the Maunder Minimum
and the subsequent secular evolution of solar activity. The goal of
this Perspective is to review recent work that uses historical data to
estimate long-term solar variability, and to provide context to users of
these estimates that may not be aware of their limitations. We propose
a clear visual guide than can be used to easily assess observational
coverage for different periods, as well as the level of disagreement
between currently proposed sunspot group number series.
---------------------------------------------------------
Title: Sunspot Characteristics at the Onset of the Maunder Minimum
Based on the Observations of Hevelius
Authors: Carrasco, V. M. S.; Vaquero, J. M.; Gallego, M. C.;
Muñoz-Jaramillo, A.; de Toma, G.; Galaviz, P.; Arlt, R.; Senthamizh
Pavai, V.; Sánchez-Bajo, F.; Villalba Álvarez, J.; Gómez, J. M.
2019ApJ...886...18C Altcode: 2021arXiv210309495C
An analysis of the sunspot observations made by Hevelius during
1642-1645 is presented. These records are the only systematic sunspot
observations just before the Maunder Minimum (MM). We have studied
different phenomena meticulously recorded by Hevelius after translating
the original Latin texts. We reevaluate the observations of sunspot
groups by Hevelius during this period and obtain an average value
7% greater than that calculated from his observations given in the
current group database. Furthermore, the average of the active day
fraction obtained in this work from Hevelius’s records previous to
the MM is significantly greater than the solar activity level obtained
from Hevelius’s sunspot observations made during the MM (70% versus
30%). We also present the butterfly diagram obtained from the sunspot
positions recorded by Hevelius for the period 1642-1645. It can be
seen that no hemispheric asymmetry exists during this interval,
in contrast with the MM. Hevelius noted a ∼3-month period that
appeared to lack sunspots in early 1645 that gave the first hint of
the impending MM. Recent studies claim that the MM was not a grand
minimum period, speculating that astronomers of that time, due to the
Aristotelian ideas, did not record all sunspots that they observed,
producing thus an underestimation of the solar activity level. However,
we show that the good quality of the sunspot records made by Hevelius
indicates that his reports of sunspots were true to the observations.
---------------------------------------------------------
Title: Probabilistic Super-Resolution of Solar Magnetograms:
Generating Many Explanations and Measuring Uncertainties
Authors: Gitiaux, Xavier; Maloney, Shane A.; Jungbluth, Anna; Shneider,
Carl; Wright, Paul J.; Güneş Baydin, Atılım; Deudon, Michel; Gal,
Yarin; Kalaitzis, Alfredo; Muñoz-Jaramillo, Andrés
2019arXiv191101486G Altcode:
Machine learning techniques have been successfully applied to
super-resolution tasks on natural images where visually pleasing results
are sufficient. However in many scientific domains this is not adequate
and estimations of errors and uncertainties are crucial. To address this
issue we propose a Bayesian framework that decomposes uncertainties
into epistemic and aleatoric uncertainties. We test the validity of
our approach by super-resolving images of the Sun's magnetic field
and by generating maps measuring the range of possible high resolution
explanations compatible with a given low resolution magnetogram.
---------------------------------------------------------
Title: Single-Frame Super-Resolution of Solar Magnetograms:
Investigating Physics-Based Metrics \& Losses
Authors: Jungbluth, Anna; Gitiaux, Xavier; Maloney, Shane A.; Shneider,
Carl; Wright, Paul J.; Kalaitzis, Alfredo; Deudon, Michel; Güneş
Baydin, Atılım; Gal, Yarin; Muñoz-Jaramillo, Andrés
2019arXiv191101490J Altcode:
Breakthroughs in our understanding of physical phenomena have
traditionally followed improvements in instrumentation. Studies of the
magnetic field of the Sun, and its influence on the solar dynamo and
space weather events, have benefited from improvements in resolution
and measurement frequency of new instruments. However, in order to fully
understand the solar cycle, high-quality data across time-scales longer
than the typical lifespan of a solar instrument are required. At
the moment, discrepancies between measurement surveys prevent
the combined use of all available data. In this work, we show that
machine learning can help bridge the gap between measurement surveys
by learning to \textbf{super-resolve} low-resolution magnetic field
images and \textbf{translate} between characteristics of contemporary
instruments in orbit. We also introduce the notion of physics-based
metrics and losses for super-resolution to preserve underlying physics
and constrain the solution space of possible super-resolution outputs.
---------------------------------------------------------
Title: A deep learning virtual instrument for monitoring extreme UV
solar spectral irradiance
Authors: Szenicer, Alexandre; Fouhey, David F.; Munoz-Jaramillo,
Andres; Wright, Paul J.; Thomas, Rajat; Galvez, Richard; Jin, Meng;
Cheung, Mark C. M.
2019SciA....5.6548S Altcode:
Measurements of the extreme ultraviolet (EUV) solar spectral irradiance
(SSI) are essential for understanding drivers of space weather effects,
such as radio blackouts, and aerodynamic drag on satellites during
periods of enhanced solar activity. In this paper, we show how to
learn a mapping from EUV narrowband images to spectral irradiance
measurements using data from NASA's Solar Dynamics Observatory obtained
between 2010 to 2014. We describe a protocol and baselines for measuring
the performance of models. Our best performing machine learning (ML)
model based on convolutional neural networks (CNNs) outperforms other
ML models, and a differential emission measure (DEM) based approach,
yielding average relative errors of under 4.6% (maximum error over
emission lines) and more typically 1.6% (median). We also provide
evidence that the proposed method is solving this mapping in a way that
makes physical sense and by paying attention to magnetic structures
known to drive EUV SSI variability.
---------------------------------------------------------
Title: The need for active region disconnection in 3D kinematic
dynamo simulations
Authors: Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.
2019A&A...627A.168W Altcode: 2019arXiv190702762W
In this paper we address a discrepancy between the surface flux
evolution in a 3D kinematic dynamo model and a 2D surface flux transport
model that has been closely calibrated to the real Sun. We demonstrate
that the difference is due to the connectivity of active regions to
the toroidal field at the base of the convection zone, which is not
accounted for in the surface-only model. Initially, we consider the
decay of a single active region, firstly in a simplified Cartesian 2D
model and subsequently the full 3D model. By varying the turbulent
diffusivity profile in the convection zone, we find that increasing
the diffusivity - so that active regions are more rapidly disconnected
from the base of the convection zone - improves the evolution of the
surface field. However, if we simulate a full solar cycle, we find
that the dynamo is unable to sustain itself under such an enhanced
diffusivity. This suggests that in order to accurately model the solar
cycle, we must find an alternative way to disconnect emerging active
regions, whilst conserving magnetic flux.
---------------------------------------------------------
Title: Historical astronomical data: urgent need for preservation,
digitization enabling scientific exploration
Authors: Pevtsov, Alexei; Griffin, Elizabeth; Grindlay, Jonathan;
Kafka, Stella; Bartlett, Jennifer; Usoskin, Ilya; Mursula, Kalevi;
Gibson, Sarah; Pillet, Valentín; Burkepile, Joan; Webb, David; Clette,
Frédéric; Hesser, James; Stetson, Peter; Muñoz-Jaramillo, Andres;
Hill, Frank; Bogart, Rick; Osborn, Wayne; Longcope, Dana
2019BAAS...51c.190P Altcode: 2019arXiv190304839P; 2019astro2020T.190P
This white paper emphasizes critical importance of preservation,
digitization and scientific exploration of historical astronomical
data. It outlines the rationale, provides examples of new science
with such data, and reviews the potential losses to science if nothing
it done.
---------------------------------------------------------
Title: A Machine-learning Data Set Prepared from the NASA Solar
Dynamics Observatory Mission
Authors: Galvez, Richard; Fouhey, David F.; Jin, Meng; Szenicer,
Alexandre; Muñoz-Jaramillo, Andrés; Cheung, Mark C. M.; Wright,
Paul J.; Bobra, Monica G.; Liu, Yang; Mason, James; Thomas, Rajat
2019ApJS..242....7G Altcode: 2019arXiv190304538G
In this paper, we present a curated data set from the NASA
Solar Dynamics Observatory (SDO) mission in a format suitable for
machine-learning research. Beginning from level 1 scientific products
we have processed various instrumental corrections, down-sampled
to manageable spatial and temporal resolutions, and synchronized
observations spatially and temporally. We illustrate the use of this
data set with two example applications: forecasting future extreme
ultraviolet (EUV) Variability Experiment (EVE) irradiance from present
EVE irradiance and translating Helioseismic and Magnetic Imager
observations into Atmospheric Imaging Assembly observations. For
each application, we provide metrics and baselines for future model
comparison. We anticipate this curated data set will facilitate
machine-learning research in heliophysics and the physical sciences
generally, increasing the scientific return of the SDO mission. This
work is a direct result of the 2018 NASA Frontier Development Laboratory
Program. Please see the Appendix for access to the data set, totaling
6.5TBs.
---------------------------------------------------------
Title: DeepEM: Demonstrating a Deep Learning Approach to DEM Inversion
Authors: Wright, Paul J.; Cheung, Mark C. M.; Thomas, Rajat; Galvez,
Richard; Szenicer, Alexandre; Jin, Meng; Muñoz-Jaramillo, Andrés;
Fouhey, David
2019zndo...2587015W Altcode:
DeepEM is a (supervised) deep learning approach to differential
emission measure (DEM) inversion that is currently under
development on GitHub. This first release coincides with the
version of DeepEM demonstrated in Chapter 4 of the Machine Learning,
Statistics, and Data Mining for Heliophysics e-book (Bobra & Mason
2018). Within the chapter (and the code provided here, DeepEM.ipynb)
we demonstrate how a simple implementation of supervised learning
can be used to reconstruct DEM maps from SDO/AIA data. Caveats
of this simple implementation and future work are also discussed.
The Machine Learning, Statistics, and Data Mining for Heliophysics
e-book can be accessed at https://helioml.github.io/HelioML/,
and the interactive DeepEM notebook (Chapter 4) is located at
https://helioml.github.io/HelioML/04/1/notebook.
---------------------------------------------------------
Title: The Extended Solar Cycle: Muddying the Waters of Solar/Stellar
Dynamo Modeling Or Providing Crucial Observational Constraints?
Authors: Srivastava, Abhishek K.; McIntosh, Scott W.; Arge,
N.; Banerjee, Dipankar; Dikpati, Mausumi; Dwivedi, Bhola N.;
Guhathakurta, Madhulika; Karak, B. B.; Leamon, Robert J.; Matthew,
Shibu K.; Munoz-Jaramillo, Andres; Nandy, D.; Norton, Aimee; Upton,
L.; Chatterjee, S.; Mazumder, Rakesh; Rao, Yamini K.; Yadav, Rahul
2018FrASS...5...38S Altcode: 2018arXiv180707601S
In 1844 Schwabe discovered that the number of sunspots increased and
decreased over a period of about 11 years, that variation became known
as the sunspot cycle. Almost eighty years later, Hale described the
nature of the Sun's magnetic field, identifying that it takes about 22
years for the Sun's magnetic polarity to cycle. It was also identified
that the latitudinal distribution of sunspots resembles the wings of
a butterfly showing migration of sunspots in each hemisphere that
abruptly start at mid-latitudes (about ±35(o) ) towards the Sun's
equator over the next 11 years. These sunspot patterns were shown
to be asymmetric across the equator. In intervening years, it was
deduced that the Sun (and sun-like stars) possess magnetic activity
cycles that are assumed to be the physical manifestation of a dynamo
process that results from complex circulatory transport processes in
the star's interior. Understanding the Sun's magnetism, its origin
and its variation, has become a fundamental scientific objective
the distribution of magnetism, and its interaction with convective
processes, drives various plasma processes in the outer atmosphere
that generate particulate, radiative, eruptive phenomena and shape the
heliosphere. In the past few decades, a range of diagnostic techniques
have been employed to systematically study finer scale magnetized
objects, and associated phenomena. The patterns discerned became
known as the “Extended Solar Cycle” (ESC). The patterns of the ESC
appeared to extend the wings of the activity butterfly back in time,
nearly a decade before the formation of the sunspot pattern, and to
much higher solar latitudes. In this short review, we describe their
observational patterns of the ESC and discuss possible connections
to the solar dynamo as we depart on a multi-national collaboration to
investigate the origins of solar magnetism through a blend of archived
and contemporary data analysis with the goal of improving solar dynamo
understanding and modeling.
---------------------------------------------------------
Title: Solar EUV Spectral Irradiance by Deep Learning
Authors: Wright, Paul; Galvez, Richard; Szenicer, Alexandre; Thomas,
Rajat; Jin, Meng; Fouhey, David; Cheung, Mark; Munoz-Jaramillo,
Andres; Mackintosh, Graham
2018csc..confE..90W Altcode:
Extreme UV (EUV) radiation from the Sun's transition region and
corona is an important driver for the energy balance of the Earth's
thermosphere and ionosphere. To characterise and monitor solar forcing
on this system and associated space weather impacts, the EUV Variability
Experiment (EVE) instrument onboard NASA's Solar Dynamics Observatory
(SDO) was designed to measure solar spectral irradiance (SSI) in the
0.1 to 105 nm wavelength range. As the result of an electrical short,
the MEGS-A component of EVE stopped delivering SSI data in the 5 - 35
nm wavelength range in May 2014. We demonstrate how a Residual Neural
Network (ResNet) augmented with a Multi-Layer Perceptron (MLP) can
fill this gap using narrowband UV and EUV images from the Atmospheric
Imaging Assembly (AIA) on SDO. As a performance benchmark, we also show
how our deep learning approach outperforms a physics model based on
differential emission measure inversions. This work was performed at
NASA's Frontier Development Lab, a public-private initiative to apply
AI techniques to accelerate space science discovery and exploration.
---------------------------------------------------------
Title: How Many Active Regions Are Necessary to Predict the Solar
Dipole Moment?
Authors: Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.
2018ApJ...863..116W Altcode: 2018arXiv180701617W
We test recent claims that the polar field at the end of Cycle 23 was
weakened by a small number of large, abnormally oriented regions, and
investigate what this means for solar cycle prediction. We isolate the
contribution of individual regions from magnetograms for Cycles 21, 22,
and 23 using a 2D surface flux transport model, and find that although
the top ∼10% of contributors tend to define sudden large variations
in the axial dipole moment, the cumulative contribution of many weaker
regions cannot be ignored. To recreate the axial dipole moment to a
reasonable degree, many more regions are required in Cycle 23 than
in Cycles 21 and 22 when ordered by contribution. We suggest that
the negative contribution of the most significant regions of Cycle
23 could indeed be a cause of the weak polar field at the following
cycle minimum and the low-amplitude Cycle 24. We also examine the
relationship between a region’s axial dipole moment contribution and
its emergence latitude, flux, and initial axial dipole moment. We find
that once the initial dipole moment of a given region has been measured,
we can predict the long-term dipole moment contribution using emergence
latitude alone.
---------------------------------------------------------
Title: A Two Dimensional Prediction of Solar Cycle 25
Authors: Munoz-Jaramillo, A.; Martens, P. C.
2017AGUFMSH13A2469M Altcode:
To this date solar cycle most cycle predictions have focused on the
forecast of solar cycle amplitude and cycle bell-curve shape. However,
recent intriguing observational results suggest that all solar cycles
follow the same longitudinal path regardless of their amplitude,
and have a very similar decay once they reach a sufficient level
of maturity. Cast in the light of our current understanding, these
results suggest that the toroidal fields inside the Sun are subject
to a very high turbulent diffusivity (of the order of magnitude of
mixing-length estimates), and their equatorward propagation is driven
by a steady meridional flow. Assuming this is the case, we will revisit
the relationship between the polar fields at minimum and the amplitude
of the next cycle and deliver a new generation of polar-field based
predictions that include the depth of the minimum, as well as the
latitude and time of the first active regions of solar cycle 25.
---------------------------------------------------------
Title: Evolution of Our Understanding of the Solar Dynamo During
Solar Cycle 24
Authors: Munoz-Jaramillo, A.
2017AGUFMSH11C..01M Altcode:
Solar cycle 24 has been an exciting cycle for our understanding of
the solar dynamo: 1. It was the first cycle for which dynamo based
predictions were ever used teaching us valuable lessons. 2. It has given
us the opportunity to observe a deep minimum and a weak cycle with a
high level of of observational detail . 3. It is full of breaktrhoughs
in anelastic MHD dynamo simulations (regular cycles, buoyant flux-tubes,
mounder-like events). 4. It has seen the creation of bridges between the
kinematic flux-transport and anelastic MHD approaches. 5. It has ushered
a new generation of realistic surface flux-transport simulations 6. We
have achieved significant observational progress in our understanding
of solar cycle propagation. The objective of this talk is to highlight
some of the most important results, giving special emphasis on what
they have taught us about solar cycle predictability.
---------------------------------------------------------
Title: Modeling Geomagnetic Variations using a Machine Learning
Framework
Authors: Cheung, C. M. M.; Handmer, C.; Kosar, B.; Gerules, G.;
Poduval, B.; Mackintosh, G.; Munoz-Jaramillo, A.; Bobra, M.; Hernandez,
T.; McGranaghan, R. M.
2017AGUFMSM23A2591C Altcode:
We present a framework for data-driven modeling of Heliophysics time
series data. The Solar Terrestrial Interaction Neural net Generator
(STING) is an open source python module built on top of state-of-the-art
statistical learning frameworks (traditional machine learning methods as
well as deep learning). To showcase the capability of STING, we deploy
it for the problem of predicting the temporal variation of geomagnetic
fields. The data used includes solar wind measurements from the OMNI
database and geomagnetic field data taken by magnetometers at US
Geological Survey observatories. We examine the predictive capability
of different machine learning techniques (recurrent neural networks,
support vector machines) for a range of forecasting times (minutes
to 12 hours). STING is designed to be extensible to other types
of data. We show how STING can be used on large sets of data from
different sensors/observatories and adapted to tackle other problems
in Heliophysics.
---------------------------------------------------------
Title: Parameter optimization for surface flux transport models
Authors: Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie,
G. J. D.
2017A&A...607A..76W Altcode: 2017arXiv170801098W
Accurate prediction of solar activity calls for precise calibration
of solar cycle models. Consequently we aim to find optimal parameters
for models which describe the physical processes on the solar surface,
which in turn act as proxies for what occurs in the interior and provide
source terms for coronal models. We use a genetic algorithm to optimize
surface flux transport models using National Solar Observatory (NSO)
magnetogram data for Solar Cycle 23. This is applied to both a 1D model
that inserts new magnetic flux in the form of idealized bipolar magnetic
regions, and also to a 2D model that assimilates specific shapes of
real active regions. The genetic algorithm searches for parameter
sets (meridional flow speed and profile, supergranular diffusivity,
initial magnetic field, and radial decay time) that produce the best
fit between observed and simulated butterfly diagrams, weighted by
a latitude-dependent error structure which reflects uncertainty in
observations. Due to the easily adaptable nature of the 2D model, the
optimization process is repeated for Cycles 21, 22, and 24 in order
to analyse cycle-to-cycle variation of the optimal solution. We find
that the ranges and optimal solutions for the various regimes are in
reasonable agreement with results from the literature, both theoretical
and observational. The optimal meridional flow profiles for each regime
are almost entirely within observational bounds determined by magnetic
feature tracking, with the 2D model being able to accommodate the
mean observed profile more successfully. Differences between models
appear to be important in deciding values for the diffusive and decay
terms. In like fashion, differences in the behaviours of different
solar cycles lead to contrasts in parameters defining the meridional
flow and initial field strength.
---------------------------------------------------------
Title: Polar Facular Observations by the Zurich Observatory: A Window
to the Evolution of the Polar Fields during the Weakest Cycles of
the Last 200 Years
Authors: Vargas-Acosta, Juan Pablo; Munoz-Jaramillo, Andres; Vargas
Dominguez, Santiago; Svalgaard, Leif
2017SPD....48.0501V Altcode:
The solar polar magnetic fields are believed to be a surface
manifestation of the large-scale field that acts as the seed for
each solar cycle. Because of this, they have received a lot of recent
attention as the best proxy for solar cycle prediction.Polar magnetic
fields have been measured systematically since the 1970s and polar
facular counts (which are directly correlated with polar field strength)
have been used to infer the evolution of the polar fields going back to
1906. However, this period does not cover the solar minima of cycle 12
and 13 which preceded the weakest cycles of the last 200 years. These
cycles are of great interest due to their similarity with solar cycle
24, which was preceded by the deepest minimum observed so far during
the space age.Here we present the results of a project to count polar
faculae using recently digitized and released observations taken by
the Zurich Observatory (1887 to 1937). These observations have the
potential of extending our proxy for the polar fields further back
into this period of great interest and help us test the validity of
our understanding.
---------------------------------------------------------
Title: The Harm that Underestimation of Uncertainty Does to Our
Community: A Case Study Using Sunspot Area Measurements
Authors: Munoz-Jaramillo, Andres
2017SPD....4820704M Altcode:
Data products in heliospheric physics are very often provided
without clear estimates of uncertainty. From helioseismology in
the solar interior, all the way to in situ solar wind measurements
beyond 1AU, uncertainty estimates are typically hard for users to
find (buried inside long documents that are separate from the data
products), or simply non-existent.There are two main reasons why
uncertainty measurements are hard to find:1. Understanding instrumental
systematic errors is given a much higher priority inside instrumental
teams.2. The desire to perfectly understand all sources of uncertainty
postpones indefinitely the actual quantification of uncertainty in our
measurements.Using the cross calibration of 200 years of sunspot area
measurements as a case study, in this presentation we will discuss the
negative impact that inadequate measurements of uncertainty have on
users, through the appearance of toxic and unnecessary controversies,
and data providers, through the creation of unrealistic expectations
regarding the information that can be extracted from their data. We
will discuss how empirical estimates of uncertainty represent a very
good alternative to not providing any estimates at all, and finalize
by discussing the bare essentials that should become our standard
practice for future instruments and surveys.
---------------------------------------------------------
Title: Update on a Solar Magnetic Catalog Spanning Four Solar Cycles
Authors: Vargas-Acosta, Juan Pablo; Munoz-Jaramillo, Andres; Vargas
Dominguez, Santiago; Werginz, Zachary; DeLuca, Michael D.; Longcope,
Dana; Harvey, J. W.; Windmueller, John; Zhang, Jie; Martens, Petrus C.
2017SPD....4811202V Altcode:
Bipolar magnetic regions (BMRs) are the cornerstone of solar
cycle propagation, the building blocks that give structure to the
solar atmosphere, and the origin of the majority of space weather
events. However, in spite of their importance, there is no homogeneous
BMR catalog spanning the era of systematic solar magnetic field
measurements. Here we present the results of an ongoing project to
address this deficiency applying the Bipolar Active Region Detection
(BARD) code to magnetograms from the 512 Channel of the Kitt Peak
Vaccum Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically
identifies BMRs and tracks them as they are rotated by differential
rotation. The output of the automatic detection is supervised by a human
observer to correct possible mistakes made by the automatic algorithm
(like incorrect pairings and tracking mislabels). Extra passes are made
to integrate fragmented regions as well as to balance the flux between
BMR polarities. At the moment, our BMR database includes nearly 10,000
unique objects (detected and tracked) belonging to four separate solar
cycles (21-24).
---------------------------------------------------------
Title: Mi Gauss es su Gauss: Lessons from Cross-Calibrating 40 years
of Full Disk Magnetograms
Authors: Werginz, Zachary; Munoz-Jaramillo, Andres; Martens, Petrus
C.; Harvey, J. W.
2017SPD....4811102W Altcode:
Full-disk line-of-sight magnetograms from the Kitt Peak Vacuum Telescope
(KPVT) are a highly valuable, but underutilized, source of data for
understanding long-term solar variability. Here we present the results
of a project for obtaining a cross-callibrated series of magnetograms
spanning 40 years including KPVT (512 and SPMG), SOHO/MDI and SDO/HMI
magnetographs. The biggest challenge we face is empirically identifying
a calibration factor and estimate of uncertainty between instruments
with little temporal overlap.Here we propose a method that fragments
magnetograms into spherical quadrangles bounded by latitudes and
longitudes and calculates various information such as total area, mean
flux density, and distance from disk center. Our main assumption is that
the Sun does not change significantly over daily time periods.First
a magnetogram to be calibrated is differentially rotated to match
a reference magnetogram in time. Then the smaller magnetogram is
interpolated into the larger one to account for sub-pixel heliographic
coordinates. We then produce equally spaced bands of latitude and
longitude determined from a fragmentation parameter. These are used
to map out regions on each magnetogram that are expected to relay
the same information. Our efforts to cross-calibrate lead to results
that vary with fragmentation parameters, the difference in time of
selected magnetograms, and distance from disk center.Given that this
cross-callibrated series will be made publically available, we are
looking for constructive criticism, suggestions, and feedback. Please
join us in making these data as good as they can be.
---------------------------------------------------------
Title: Addressing Systematic Errors in Correlation Tracking on
HMI Magnetograms
Authors: Mahajan, Sushant S.; Hathaway, David H.; Munoz-Jaramillo,
Andres; Martens, Petrus C.
2017SPD....4820702M Altcode:
Correlation tracking in solar magnetograms is an effective method to
measure the differential rotation and meridional flow on the solar
surface. However, since the tracking accuracy required to successfully
measure meridional flow is very high, small systematic errors have a
noticeable impact on measured meridional flow profiles. Additionally,
the uncertainties of this kind of measurements have been historically
underestimated, leading to controversy regarding flow profiles at
high latitudes extracted from measurements which are unreliable
near the solar limb.Here we present a set of systematic errors we
have identified (and potential solutions), including bias caused by
physical pixel sizes, center-to-limb systematics, and discrepancies
between measurements performed using different time intervals. We have
developed numerical techniques to get rid of these systematic errors
and in the process improve the accuracy of the measurements by an order
of magnitude.We also present a detailed analysis of uncertainties in
these measurements using synthetic magnetograms and the quantification
of an upper limit below which meridional flow measurements cannot be
trusted as a function of latitude.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Polar network index for the solar
cycle studies (Priyal+, 2014)
Authors: Priyal, M.; Banerjee, D.; Karak, B. B.; Munoz-Jaramillo,
A.; Ravindra, B.; Choudhuri, A. R.; Singh, J.
2017yCat..17939004P Altcode:
The spatial resolution of the Ca K spectroheliograms taken at
Kodaikanal (hereafter KKL) is about 2 arcsec and the exit slit of the
spectroheliograph yields a spectral window of 0.5 Å centered at the
Ca-K line at 3933.67 Å. Ermoli et al. (2009ApJ...698.1000E) pointed
out that the Kodaikanal archive hosts the longest homogeneous record,
with fewer variations in spatial resolution. The earlier version of the
8 bit data at Kodaikanal is sufficient to study those plage area with
high intensity contrast, but does not provide the required photometric
accuracy to properly identify the network structures because of the
small intensity contrast of these features. Therefore, we have designed
and developed two digitizer units, using a 1 m labsphere with an exit
port of 350 mm which provides a stable and uniform source of light
with less than 1% variation from the center to the edge of the light
source. The CCD camera with 4kx4k format, a pixel size of 15 u square,
and a 16 bit read out, operating at temperature of -100°C, was used
to digitize the images. The Ca-K network can be clearly seen because
of the high spatial resolution of digitization (0.86 arcsec). <P />(4
data files).
---------------------------------------------------------
Title: A Detailed Reconstruction of Solar Activity During the
Maunder Minimum
Authors: Munoz-Jaramillo, A.; Sanchez-Carrasco, V.; Vaquero, J. M.
2016AGUFMSH43D2589M Altcode:
Besides its decadal modulation, the solar cycle presents long-term
secular changes in the amplitude of adjacent cycles that drive
long-term changes in the heliospheric environment and have been
suggested to drive long-term changes in terrestrial seasonal
weather. The best well known of these secular changes is the Maunder
Minimum (1645-1715), which coincided with an interval of very cold
winters in Europe. Unfortunately, this period is characterized by a
significant lack of telescopic observations and thus suffers from a
very high level of observational uncertainty. In this presentation we
will discuss recent efforts to increase the observational reliability
of observations during the Maunder Minimum, by taking advantage of
observational redundance, the analysis of these observations to place
strict constraints on solar activity during the Maunder Minimum,
by comparing with modern observations, and the implications these
results have for our understanding of the solar dynamo.
---------------------------------------------------------
Title: Development of a Homogenous Database of Bipolar Active Regions
Spanning Four Cycles
Authors: Munoz-Jaramillo, A.; Werginz, Z. A.; Vargas-Acosta, J. P.;
DeLuca, M. D.; Vargas-Dominguez, S.; Lamb, D. A.; DeForest, C. E.;
Longcope, D. W.; Martens, P.
2016AGUFMSH11A2219M Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).In
this presentation we discuss an ongoing project to address this
deficiency by applying our Bipolar Active Region Detection (BARD)
code on full disk magnetograms measured by the 512 (1975-1993) and
SPMG (1992-2003) instruments at the Kitt Peak Vacuum Telescope (KPVT),
SOHO/MDI (1996-2011) and SDO/HMI (2010-present). First we will discuss
the results of our revitalization of 512 and SPMG KPVT data, then
we will discuss how our BARD code operates, and finally report the
results of our cross-callibration across instruments.The corrected
and improved KPVT magnetograms will be made available through the
National Solar Observatory (NSO) and Virtual Solar Observatory (VSO),
including updated synoptic maps produced by running the corrected KPVT
magnetograms though the SOLIS pipeline. The homogeneous active region
database will be made public by the end of 2017 once it has reached
a satisfactory level of quality and maturity. The Figure shows all
bipolar active regions present in our database (as of Aug 2016) colored
according to the instrument where they were detected. The image also
includes the names of the NSF-REU students in charge of the supervision
of the detection algorithm and the year in which they worked on the
catalog. Marker size is indicative of the total active region flux.
---------------------------------------------------------
Title: The best of both worlds: Using automatic detection and limited
human supervision to create a homogenous magnetic catalog spanning
four solar cycles
Authors: Muñoz-Jaramillo, Andres; Werginz, Zachary; Vargas-Acosta,
Juan Pablo; DeLuca, Michael; Windmueller, J. C.; Zhang, Jie; Longcope,
Dana; Lamb, Derek; DeForest, Craig; Vargas-Domínguez, Santiago;
Harvey, Jack; Martens, Piet
2016bida.conf.3194M Altcode: 2022arXiv220311908M
Bipolar magnetic regions (BMRs) are the cornerstone of solar
variability. They are tracers of the large-scale magnetic processes
that give rise to the solar cycle, shapers of the solar corona,
building blocks of the large-scale solar magnetic field, and significant
contributors to the free-energetic budget that gives rise to flares and
coronal mass ejections. Surprisingly, no homogeneous catalog of BMRs
exists today, in spite of the existence of systematic measurements of
the magnetic field since the early 1970's. The purpose of this work is
to address this deficiency by creating a homogenous catalog of BMRs
from the 1970's until the present. For this purpose, in this paper
we discuss the strengths and weaknesses of the automatic and manual
detection of BMRs and how both methods can be combined to form the basis
of our Bipolar Active Region Detection (BARD) code and its supporting
human supervision module. At present, the BARD catalog contains more
than 10,000 unique BMRs tracked and characterized during every day
of their observation. Here we also discuss our future plans for the
creation of an extended multi-scale magnetic catalog combining the
SWAMIS and BARD catalogs.
---------------------------------------------------------
Title: Advances on Our Understanding of Solar Cycle Propagation
and Predictability
Authors: Muñoz-Jaramillo, Andrés
2016usc..confE..88M Altcode:
As solar cycle 24 winds down and we start looking forward to the coming
cycle 25, we are steadily approaching the time in which a new host
of solar cycle predictions will be made. The point of this talk is to
highlight some of the most important advances in our understanding of
cycle propagation and its predictability (made since the last round
of cycle predictions). In particular, this presentation will focus
on theoretical and observational evidence in favor of a dynamo that
relies on active region emergence and decay for its operation, and on
evidence of a causal disconnection that takes place between one cycle
and the next (making inter-cyclic prediction difficult)
---------------------------------------------------------
Title: Developing a Solar Magnetic Catalog Spanning Four Cycles
Authors: Werginz, Zachary; Munoz-Jaramillo, Andres; DeLuca, Michael
D.; Vargas Acosta, Juan Pablo; Vargas Dominguez, Santiago; Zhang,
Jie; Longcope, Dana; Martens, Petrus C.
2016SPD....4740502W Altcode:
Bipolar magnetic regions (BMRs) are the cornerstone of solar
cycle propagation, the building blocks that give structure to the
solar atmosphere, and the origin of the majority of space weather
events. However, in spite of their importance, there is no homogeneous
BMR catalog spanning the era of systematic solar magnetic field
measurements. Here we present the results of an ongoing project to
address this deficiency applying the Bipolar Active Region Detection
(BARD) code to magnetograms from the 512 Channel of the Kitt Peak Vaccum
Telescope, SOHO/MDI, and SDO/HMI.The BARD code automatically identifies
BMRs and tracks them as they are rotated by differential rotation. The
output of the automatic detection is supervised by a human observer
to correct possible mistakes made by the automatic algorithm (like
incorrect pairings and tracking mislabels). Extra passes are made to
integrate fragmented regions as well as to balance the flux between
BMR polarities. At the moment, our BMR database includes 6,885 unique
objects (detected and tracked) belonging to four separate solar cycles
(21-24).
---------------------------------------------------------
Title: An Emerging Magnetic Flux Catalog for SOHO/MDI
Authors: Lamb, Derek; Munoz-Jaramillo, Andres; DeForest, Craig
2016SPD....4730701L Altcode:
We present a catalog of emerging magnetic flux events covering
the entirety of the 15-year-long SOHO/MDI 96-minute magnetogram
dataset. Such a catalog has myriad uses in studies of the solar
dynamo and solar cycle. Our catalog is designed to mimic as nearly
as possible the Emerging Flux region catalog produced for SDO/HMI,
allowing continuity across missions and solar cycles. We will present
details of the algorithm for identifying emerging flux events, special
considerations for MDI as opposed to HMI, detailed examples of some
detected emerging flux regions, and a brief overview of statistics
of the entire catalog. The catalog will be available for querying
through the Heliophysics Event Knowledgebase, as well as for direct
downloading from Southwest Research Institute. This work has been
supported by NASA Grant NNX14AJ67G through the Heliophysics Data
Environment Enhancements program.
---------------------------------------------------------
Title: Where Do Data Go When They Die? Attaining Data Salvation
Through the Establishment of a Solar Dynamo Dataverse
Authors: Munoz-Jaramillo, Andres
2016SPD....4740801M Altcode:
The arrival of a highly interconnected digital age with practically
limitless data storage capacity has brought with it a significant
shift in which scientific data is stored and distributed (i.e. from
being in the hands of a small group of scientists to being openly and
freely distributed for anyone to use). However, the vertiginous speed
at which hardware, software, and the nature of the internet changes
has also sped up the rate at which data is lost due to formatting
obsolescence and loss of access.This poster is meant to advertise the
creation of a highly permanent data repository (within the context of
Harvard's Dataverse), curated to contain datasets of high relevance
for the study, and prediction of the solar dynamo, solar cycle, and
long-term solar variability. This repository has many advantages over
traditional data storage like the assignment of unique DOI identifiers
for each database (making it easier for scientist to directly cite
them), and the automatic versioning of each database so that all data
are able to attain salvation.
---------------------------------------------------------
Title: Contextualizing Solar Cycle 24: Report on the Development of
a Homogenous Database of Bipolar Active Regions Spanning Four Cycles
Authors: Munoz-Jaramillo, A.; Werginz, Z. A.; DeLuca, M. D.;
Vargas-Acosta, J. P.; Longcope, D. W.; Harvey, J. W.; Martens, P.;
Zhang, J.; Vargas-Dominguez, S.; DeForest, C. E.; Lamb, D. A.
2015AGUFMSH33D..06M Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).In
this presentation we discuss an ongoing project to address this
deficiency by applying our Bipolar Active Region Detection (BARD)
code on full disk magnetograms measured by the 512 (1975-1993) and
SPMG (1992-2003) instruments at the Kitt Peak Vacuum Telescope (KPVT),
SOHO/MDI (1996-2011) and SDO/HMI (2010-present). First we will discuss
the results of our revitalization of 512 and SPMG KPVT data, then we
will discuss how our BARD code operates, and finally report the results
of our cross-callibration.The corrected and improved KPVT magnetograms
will be made available through the National Solar Observatory (NSO)
and Virtual Solar Observatory (VSO), including updated synoptic maps
produced by running the corrected KPVT magnetograms though the SOLIS
pipeline. The homogeneous active region database will be made public
by the end of 2017 once it has reached a satisfactory level of quality
and maturity. The Figure shows all bipolar active regions present in
our database (as of Aug 2015) colored according to the sign of their
leading polarity. Marker size is indicative of the total active region
flux. Anti-Hale regions are shown using solid markers.
---------------------------------------------------------
Title: The Minimum of Solar Cycle 23: As Deep as It Could Be?
Authors: Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Longcope,
Dana W.; Tlatov, Andrey G.; Pevtsov, Alexei A.; Balmaceda, Laura A.;
DeLuca, Edward E.; Martens, Petrus C. H.
2015ApJ...804...68M Altcode: 2015arXiv150801222M
In this work we introduce a new way of binning sunspot group data
with the purpose of better understanding the impact of the solar
cycle on sunspot properties and how this defined the characteristics
of the extended minimum of cycle 23. Our approach assumes that
the statistical properties of sunspots are completely determined
by the strength of the underlying large-scale field and have no
additional time dependencies. We use the amplitude of the cycle
at any given moment (something we refer to as activity level) as a
proxy for the strength of this deep-seated magnetic field. We find
that the sunspot size distribution is composed of two populations:
one population of groups and active regions and a second population
of pores and ephemeral regions. When fits are performed at periods
of different activity level, only the statistical properties of the
former population, the active regions, are found to vary. Finally,
we study the relative contribution of each component (small-scale
versus large-scale) to solar magnetism. We find that when hemispheres
are treated separately, almost every one of the past 12 solar minima
reaches a point where the main contribution to magnetism comes from
the small-scale component. However, due to asymmetries in cycle phase,
this state is very rarely reached by both hemispheres at the same
time. From this we infer that even though each hemisphere did reach
the magnetic baseline, from a heliospheric point of view the minimum
of cycle 23 was not as deep as it could have been.
---------------------------------------------------------
Title: The Minimum of Solar Cycle 23: As Deep as It Could Be?
Authors: Munoz-Jaramillo, Andres; Senkpeil, Ryan; Longcope, Dana;
Tlatov, Andrey; Pevtsov, Alexei A.; Balmaceda, Laura; DeLuca, Edward
E.; Martens, Petrus C.
2015TESS....130803M Altcode:
After a lull lasting more than 60 years of seemly uniform solar minima,
the solar minimum of solar cycle 23 came as a great surprise due to its
depth, duration, and record lows in a wide variety of solar activity
indices and solar wind properties. One of the consequence of such an
event is the revival of the interest in extreme minima, grand minima,
and the identification of a solar basal state of minimum magnetic
activity.In this presentation we will discuss a new way of binning
sunspot group data, with the purpose of better understanding the impact
of the solar cycle on sunspot properties, and how this defined the
characteristics of the extended minimum of cycle 23. Our main result
is centered around the fact that the sunspot size distribution is
composed of two populations, a population of groups and active regions,
and second of pores and ephemeral regions. We find that only the
properties of the former population, the active regions, is found to
vary with the solar cycle, while the propeties of pores and ephemeral
regions does not.Taking advantage of our statistical characterization
we probe the question of the solar baseline magnetism. We find that,
when hemispheres are treated separately, almost every one of the past
12 solar minima reaches such a point. However, due to asymmetries in
cycle phase, the basal state is very rarely reached by both hemispheres
at the same time. From this we infer that, even though each hemisphere
did reach the magnetic baseline, from a heliospheric point of view
the minimum of cycle 23 was not as deep as it could have been.
---------------------------------------------------------
Title: Vitalizing four solar cycles of Kitt Peak synoptic magnetograms
Authors: Harvey, John; Munoz-Jaramillo, Andres
2015TESS....111102H Altcode:
Solar magnetism spans many decades of spatial and temporal
scales. Studies of the larger end of these ranges requires frequent
observations of the full solar disk over long durations. To aid
investigations of the solar cycle and individual active region
evolution, nearly daily magnetograms have been observed from Kitt Peak
during solar cycles 20-23. These data were used in real time for space
weather predictions, and archived observations have so far served more
than 1500 refereed research publications. Some of the observations
suffered from various instrumental problems. We report ongoing efforts
to restore and correct observations from 1970-2003 in order to maximize
the scientific value of the observations. The main improvements are
reductions of certain instrumental noise, signal biases, and imperfect
scanning geometry. The improved data will be used the make synchronic
and diachronic synoptic maps, a catalog of active region properties,
and estimates of tracer flow patterns.In addition to base funding
from NSF, NASA and NOAA provided substantial support of the Kitt Peak
synoptic observations.
---------------------------------------------------------
Title: Small-scale and Global Dynamos and the Area and Flux
Distributions of Active Regions, Sunspot Groups, and Sunspots:
A Multi-database Study
Authors: Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Windmueller,
John C.; Amouzou, Ernest C.; Longcope, Dana W.; Tlatov, Andrey G.;
Nagovitsyn, Yury A.; Pevtsov, Alexei A.; Chapman, Gary A.; Cookson,
Angela M.; Yeates, Anthony R.; Watson, Fraser T.; Balmaceda, Laura A.;
DeLuca, Edward E.; Martens, Petrus C. H.
2015ApJ...800...48M Altcode: 2014arXiv1410.6281M
In this work, we take advantage of 11 different sunspot group,
sunspot, and active region databases to characterize the area
and flux distributions of photospheric magnetic structures. We
find that, when taken separately, different databases are better
fitted by different distributions (as has been reported previously
in the literature). However, we find that all our databases can be
reconciled by the simple application of a proportionality constant,
and that, in reality, different databases are sampling different
parts of a composite distribution. This composite distribution
is made up by linear combination of Weibull and log-normal
distributions—where a pure Weibull (log-normal) characterizes the
distribution of structures with fluxes below (above) 10<SUP>21</SUP>Mx
(10<SUP>22</SUP>Mx). Additionally, we demonstrate that the Weibull
distribution shows the expected linear behavior of a power-law
distribution (when extended to smaller fluxes), making our results
compatible with the results of Parnell et al. We propose that this is
evidence of two separate mechanisms giving rise to visible structures
on the photosphere: one directly connected to the global component of
the dynamo (and the generation of bipolar active regions), and the other
with the small-scale component of the dynamo (and the fragmentation of
magnetic structures due to their interaction with turbulent convection).
---------------------------------------------------------
Title: Automatic vs. Human Detection of Bipolar Magnetic Regions:
Using the Best of Both Worlds
Authors: Munoz-Jaramillo, A.; DeLuca, M. D.; Windmueller, J. C.;
Longcope, D. W.
2014AGUFMSH34A..04M Altcode:
The solar cycle can be understood as a process that alternates the
large-scale magnetic field of the Sun between poloidal and toroidal
configurations. Although the process that transitions the solar cycle
between toroidal and poloidal phases is still not fully understood,
theoretical studies, and observational evidence, suggest that this
process is driven by the emergence and decay of bipolar magnetic
regions (BMRs) at the photosphere. Furthermore, the emergence of
BMRs at the photosphere is the main driver behind solar variability
and solar activity in general; making the study of their properties
doubly important for heliospheric physics. However, in spite of their
critical role, there is still no unified catalog of BMRs spanning
multiple instruments and covering the entire period of systematic
measurement of the solar magnetic field (i.e. 1975 to present).One
of the interesting aspects of the detection of BMRs is that, due to
the time and spatial scales of interest, it is tractable for both
human observers and automatic detection algorithms. This makes it
ideal for comparative studies of the advantages and failing of both
approaches. In this presentation we will compare three different BMR
catalogs, reduced from magnetograms taken by SOHO/MDI, using human,
automatic, and hybrid methods of detection. The focus will be the
comparative performance between the three methods, their merits, and
disadvantages, and the lessons that can be applied to other imaging
data sets.
---------------------------------------------------------
Title: Polar Network Index as a Magnetic Proxy for the Solar Cycle
Studies
Authors: Priyal, Muthu; Banerjee, Dipankar; Karak, Bidya Binay;
Muñoz-Jaramillo, Andrés; Ravindra, B.; Choudhuri, Arnab Rai;
Singh, Jagdev
2014ApJ...793L...4P Altcode: 2014arXiv1407.4944P
The Sun has a polar magnetic field which oscillates with the 11 yr
sunspot cycle. This polar magnetic field is an important component
of the dynamo process which operates in the solar convection zone and
produces the sunspot cycle. We have direct systematic measurements of
the Sun's polar magnetic field only from about the mid-1970s. There are,
however, indirect proxies which give us information about this field
at earlier times. The Ca-K spectroheliograms taken at the Kodaikanal
Solar Observatory during 1904-2007 have now been digitized with 4k
× 4k CCD and have higher resolution (~0.86 arcsec) than the other
available historical data sets. From these Ca-K spectroheliograms,
we have developed a completely new proxy (polar network index,
hereafter PNI) for the Sun's polar magnetic field. We calculate PNI
from the digitized images using an automated algorithm and calibrate
our measured PNI against the polar field as measured by the Wilcox
Solar Observatory for the period 1976-1990. This calibration allows
us to estimate the polar fields for the earlier period up to 1904. The
dynamo calculations performed with this proxy as input data reproduce
reasonably well the Sun's magnetic behavior for the past century.
---------------------------------------------------------
Title: Statistical Constraints on Joy's Law
Authors: Amouzou, Ernest C.; Munoz-Jaramillo, Andres; Martens, Petrus
C.; DeLuca, Edward E.
2014AAS...22421829A Altcode:
Using sunspot data from the observatories at Mt. Wilson and Kodaikanal,
active region tilt angles are analyzed for different active region
sizes and latitude bins. A number of similarly-shaped statistical
distributions were fitted to the data using maximum likelihood
estimation. In all cases, we find that the statistical distribution
best describing the number of active regions at a given tilt angle is a
Laplace distribution with the form (2β)<SUP>-1</SUP>*exp(-|x-μ|/β),
with 2° ≤ μ ≤ 11°, and 10° ≤ β ≤ 40°.
---------------------------------------------------------
Title: From the Tachocline Into the Heliosphere: Coupling a 3D
kinematic dynamo to the CCMC
Authors: Munoz-Jaramillo, Andres; Yeates, Anthony R; Martens, Petrus
C.; DeLuca, Edward E.
2014AAS...22421103M Altcode:
During the last decade, axisymmetric kinematic dynamo models have
contributed greatly to our understanding of the solar cycle. However,
with the advent of more powerful computers the limitation to axisymmetry
has been lifted. Here we present a 3D kinematic dynamo model where
active regions are driven by velocity perturbations calibrated to
reproduce observed active region properties (including the size and
flux of active regions, and the distribution of tilt angle with
latitude), resulting in a more consistent treatment of flux-tube
emergence in kinematic dynamo models than artificial flux deposition. We
demonstrate how this technique can be used to assimilate active region
observations obtained from the US National Solar Observatory/Kitt Peak
(NSO/KP) synoptic magnetograms and how our model couples naturally
with heliospheric models, paving the way for the simultaneous study
of the evolution of the magnetic field in the solar interior as well
as its impact on the heliosphere.
---------------------------------------------------------
Title: From the tachocline into the heliosphere: coupling a 3D
kinematic dynamo to coronal models
Authors: Yeates, Anthony; Munoz-Jaramillo, Andres
2014cosp...40E3715Y Altcode:
During the last decade, axisymmetric kinematic dynamo models have
contributed greatly to our understanding of the solar cycle. However,
with the advent of more powerful computers the limitation to
axisymmetry has been lifted. Here we present a 3D kinematic dynamo
model where active regions are driven by velocity perturbations
calibrated to reproduce observed active region properties (including
the size and flux of active regions, and the distribution of tilt
angle with latitude), resulting in a more consistent treatment of
flux-tube emergence in kinematic dynamo models than artificial flux
deposition. We demonstrate how this technique can be used to assimilate
active region observations from US National Solar Observatory/Kitt Peak
(NSO/KP) synoptic magnetograms, and how our model couples naturally
with three-dimensional simulations of the Sun's coronal magnetic
field. This paves the way for the simultaneous study of the evolution
of the magnetic field in the solar interior as well as its impact on
the heliosphere.
---------------------------------------------------------
Title: Helioseismic Perspective of the Solar Dynamo
Authors: Muñoz-Jaramillo, A.; Martens, P. C. H.; Nandy, D.
2013ASPC..478..271M Altcode:
Helioseismology has been, without a doubt, one of the greatest
contributors to our understanding of the solar cycle. In particular,
its results have been critical in the development of solar dynamo
models, by providing modelers with detailed information about the
internal, large scale flows of solar plasma. <P />This review will
give a historical overview of the evolution of our understanding of the
solar cycle, placing special emphasis on advances driven by helioseismic
results. We will discuss some of the outstanding modeling issues, and
discuss how Helioseismology can help push our understanding forward
during the next decade.
---------------------------------------------------------
Title: Kinematic active region formation in a three-dimensional
solar dynamo model
Authors: Yeates, A. R.; Muñoz-Jaramillo, A.
2013MNRAS.436.3366Y Altcode: 2013arXiv1309.6342Y; 2013MNRAS.tmp.2495Y
We propose a phenomenological technique for modelling the emergence
of active regions within a three-dimensional, kinematic dynamo
framework. By imposing localized velocity perturbations, we create
emergent flux tubes out of toroidal magnetic field at the base of
the convection zone, leading to the eruption of active regions at the
solar surface. The velocity perturbations are calibrated to reproduce
observed active region properties (including the size and flux of active
regions, and the distribution of tilt angle with latitude), resulting
in a more consistent treatment of flux-tube emergence in kinematic
dynamo models than artificial flux deposition. We demonstrate how this
technique can be used to assimilate observations and drive a kinematic
three-dimensional model, and use it to study the characteristics of
active region emergence and decay as a source of poloidal field. We
find that the poloidal components are strongest not at the solar
surface, but in the middle convection zone, in contrast with the
common assumption that the poloidal source is located near the solar
surface. We also find that, while most of the energy is contained in
the lower convection zone, there is a good correlation between the
evolution of the surface and interior magnetic fields.
---------------------------------------------------------
Title: Using the Dipolar and Quadrupolar Moments to Improve
Solar-Cycle Predictions Based on the Polar Magnetic Fields
Authors: Muñoz-Jaramillo, Andrés; Balmaceda, Laura A.; DeLuca,
Edward E.
2013PhRvL.111d1106M Altcode: 2013arXiv1308.2038M
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and Earth’s
upper atmosphere (commonly referred to as space weather and climate). In
recent years there has been an effort to develop accurate solar cycle
predictions, leading to nearly a hundred widely spread predictions for
the amplitude of solar cycle 24. Here we show that cycle predictions
can be made more accurate if performed separately for each hemisphere,
taking advantage of information about both the dipolar and quadrupolar
moments of the solar magnetic field during minimum.
---------------------------------------------------------
Title: Solar Cycle Propagation, Memory, and Prediction: Insights
from a Century of Magnetic Proxies
Authors: Munoz-Jaramillo, Andres; Dasi-Espuig, M.; Balmaceda, L. A.;
DeLuca, E. E.
2013SPD....4440302M Altcode:
In the simplest of forms, modern dynamo theory describes the solar cycle
as a process that takes the solar magnetic field (back and forth) from
a configuration that is predominantly poloidal (contained inside the
meridional plane), to one predominantly toroidal (wrapped around the
axis of rotation). However, there is still uncertainty and controversy
in the detailed understanding of this process. A major contributor to
this uncertainty is the lack of direct long-term databases covering
different components of the solar magnetic field (an issue mainly
affecting the poloidal component of the solar magnetic field). In
this talk we will review the different observations that can be used
as proxies for the solar magnetic field (in absence of direct magnetic
observations). I will present a recently standardized database that can
be used as a proxy for the evolution of the polar magnetic field. And
to conclude, I will show the insights that can be gained (by taking
advantage of this database) in the context of the transition between
the toroidal and poloidal phases of the cycle, solar cycle memory
as determined by the different mechanisms of flux transport, and the
practical goal of solar cycle prediction.
---------------------------------------------------------
Title: Using the dipolar and quadrupolar moments to improve solar
cycle predictions based on the polar magnetic fields
Authors: Munoz-Jaramillo, Andres; Balmaceda, L. A.; DeLuca, E. E.
2013SPD....44..129M Altcode:
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and the Earth's
upper atmosphere. These changes have a direct impact on the lifetime of
space-based assets and can create hazards to astronauts in space. In
recent years there has been an effort to develop accurate solar cycle
predictions (with aims at predicting the long-term evolution of space
weather), leading to nearly a hundred widely spread predictions for
the amplitude of solar cycle 24. In this presentation we show how cycle
predictions can be made more accurate if performed separately for each
hemisphere, taking advantage of information about both the dipolar
and quadrupolar moments of the solar magnetic field. Additionally,
by extending the relationship between polar flux at solar minimum
and the amplitude of the next cycle to encompass a full century, we
demonstrate the power of predictions based on the solar polar field --
paving the way for a new generation of better and more accurate solar
cycle predictions.
---------------------------------------------------------
Title: Solar Cycle Propagation, Memory, and Prediction: Insights
from a Century of Magnetic Proxies
Authors: Muñoz-Jaramillo, Andrés; Dasi-Espuig, María; Balmaceda,
Laura A.; DeLuca, Edward E.
2013ApJ...767L..25M Altcode: 2013arXiv1304.3151M
The solar cycle and its associated magnetic activity are the main
drivers behind changes in the interplanetary environment and Earth's
upper atmosphere (commonly referred to as space weather). These
changes have a direct impact on the lifetime of space-based assets
and can create hazards to astronauts in space. In recent years there
has been an effort to develop accurate solar cycle predictions (with
aims at predicting the long-term evolution of space weather), leading
to nearly a hundred widely spread predictions for the amplitude of
solar cycle 24. A major contributor to the disagreement is the lack
of direct long-term databases covering different components of the
solar magnetic field (toroidal versus poloidal). Here, we use sunspot
area and polar faculae measurements spanning a full century (as our
toroidal and poloidal field proxies) to study solar cycle propagation,
memory, and prediction. Our results substantiate predictions based
on the polar magnetic fields, whereas we find sunspot area to be
uncorrelated with cycle amplitude unless multiplied by area-weighted
average tilt. This suggests that the joint assimilation of tilt and
sunspot area is a better choice (with aims to cycle prediction) than
sunspot area alone, and adds to the evidence in favor of active region
emergence and decay as the main mechanism of poloidal field generation
(i.e., the Babcock-Leighton mechanism). Finally, by looking at the
correlation between our poloidal and toroidal proxies across multiple
cycles, we find solar cycle memory to be limited to only one cycle.
---------------------------------------------------------
Title: Use of a time delay dynamo model to obtain solar-like sunspot
cycles
Authors: Amouzou, E.; Nandy, D.; Muñoz-Jaramillo, A.; Martens, P.
2013ASInC..10...83A Altcode:
Using a delay-differential equation model, we simulate the solar
dynamo. We find that solar-like dynamo solutions exist in certain
parameter regimes for which the dynamo number is less than or about
equal to -3 (|N_D| > 3, N_D < 0) and that sunspot cycle periods of
11 years can be reproduced with the parameter values set at a magnetic
diffusivity of η = 3.5 × 10^{12} cm^{2}/s and a total time delay of
approximately 2.8 yr.
---------------------------------------------------------
Title: Understanding the Role of the Polar Fields on the Propagation
of the Solar Cycle
Authors: Munoz-Jaramillo, A.; DeLuca, E. E.
2012AGUFMSH13C2263M Altcode:
In addition to the well known 11-year periodicity, the solar cycle also
presents long-term modulations of its amplitude and period which play
a determinant role in the evolution of space weather and climate. To
this date, the efforts at understanding long-term solar variability
have focused on the active parts of the cycle using sunspot properties
as their main source of data. However, the recent extend minimum
of sunspot cycle 23 has shown us that the quiet parts of the cycle
are equally important and thus long-term databases complementary to
sunspot properties are necessary. Here we use a homogeneous database
of polar magnetic flux measurements going back to the beginning of
the 20th century to study the role of the polar flux in the long-term
evolution of the heliospheric magnetic field, as well as the relevance
of the polar magnetic field for the evolution of the solar cycle. We
demonstrate that the polar fields are crucial for the evolution of
both types of magnetic field and how the results presented here lay
the foundations for a new generation of sunspot cycle predictions.
---------------------------------------------------------
Title: All Quiet on the Solar Front: Origin and Heliospheric
Consequences of the Unusual Minimum of Solar Cycle 23
Authors: Nandy, D.; Muñoz-Jaramillo, A.; Martens, P. C. H.
2012SunGe...7...17N Altcode:
The magnetic activity of the Sun shapes the heliospheric space
environment through modulation of the solar wind, interplanetary
magnetic field, cosmic ray flux and solar irradiance. Sunspots -
strongly magnetized regions on the solar surface - also spawns solar
storms such as flares and coronal mass ejections which generate severe
space weather affecting space-based technologies. The Sun's magnetic
output varies in a cyclic manner going through phases of maximum and
minimum activity. Following solar cycle 23 the Sun entered a prolonged
and unusually long minimum with a large number of days without sunspots
that was unprecedented in the space age. This long phase of very low
solar activity resulted in record high cosmic ray flux at Earth, weak
solar wind speeds and low interplanetary magnetic field. We provide an
overview of this peculiar solar minimum, critically explore theories
for its origin and argue that the unusual conditions in the heliosphere
that we experienced during this minimum eventually originated in solar
internal dynamics.
---------------------------------------------------------
Title: Calibrating 100 Years of Polar Faculae Measurements:
Implications for the Evolution of the Heliospheric Magnetic Field
Authors: Muñoz-Jaramillo, Andrés; Sheeley, Neil R.; Zhang, Jie;
DeLuca, Edward E.
2012ApJ...753..146M Altcode: 2013arXiv1303.0345M
Although the Sun's polar magnetic fields are thought to provide
important clues for understanding the 11 year sunspot cycle, including
the observed variations of its amplitude and period, the current
database of high-quality polar field measurements spans relatively
few sunspot cycles. In this paper, we address this deficiency by
consolidating Mount Wilson Observatory polar faculae data from four
data reduction campaigns, validating it through a comparison with
facular data counted automatically from Michelson Doppler Imager (MDI)
intensitygrams, and calibrating it against polar field measurements
taken by the Wilcox Solar Observatory and average polar field and
total polar flux calculated using MDI line-of-sight magnetograms. Our
results show that the consolidated polar facular measurements are in
excellent agreement with both polar field and polar flux estimates,
making them an ideal proxy to study the evolution of the polar
magnetic field. Additionally, we combine this database with sunspot
area measurements to study the role of the polar magnetic flux in the
evolution of the heliospheric magnetic field (HMF). We find that there
is a strong correlation between HMF and polar flux at solar minimum
and that, taken together, polar flux and sunspot area are better
at explaining the evolution of the HMF during the last century than
sunspot area alone.
---------------------------------------------------------
Title: Use of a Time Delay Dynamo Model to Obtain Sun-Like Sunspot
Cycles
Authors: Amouzou, Ernest C.; Nandy, D.; Munoz-Jaramillo, A.; Martens,
P. C. H.
2012AAS...22020611A Altcode:
Using a time delay-based, simplified dynamo model, we attempted to
produce results characteristic of the Sun when the parameters are
set to solar values. We found that dynamo solutions exist for dynamo
numbers less than or about equal to -3 (|ND| > 3,ND < 0) and that
sunspot cycle periods of the same order of magnitude of the 11-year
sunspot cycle can be obtained when the diffusive time scale and the
total time delay are both about four years.
---------------------------------------------------------
Title: Calibration Of a Century of Polar Field Measurements and
what this Tells us About the Long-term Variability of the Solar and
Heliospheric Magnetic Field
Authors: Munoz-Jaramillo, Andres; Sheeley, N. R.; Zhang, J.; DeLuca,
E. E.
2012AAS...22012304M Altcode:
In addition to the well known 11-year periodicity, the solar cycle also
presents long-term modulations of its amplitude and period which play
a determinant role in the evolution of space weather and climate. To
this date, the efforts at understanding long-term solar variability
have focused on the active parts of the cycle using sunspot properties
as their main source of data. However, the recent extend minimum of
sunspot cycle 23 has shown us that the quiet parts of the cycle are
equally important and thus long-term databases complementary to sunspot
properties are necessary. <P />Here we show how to consolidate Mount
Wilson Observatory polar faculae data from four observational campaigns
(1906-1964, Sheeley 1966; 1960-1975, Sheeley 1976; 1975-1990, Sheeley
1991; 1985-2007, Sheeley 2008), validate it through a comparison
with facular data counted automatically from MDI intensitygrams,
and calibrate it against polar field measurements taken by the Wilcox
Solar Observatory (1977-2011) and average polar field and total polar
flux calculated using MDI line-of-sight magnetograms (1996-2011). <P
/>We also show that the consolidated polar facular measurements are
in excellent agreement with both polar field and polar flux estimates,
making them an ideal proxy to study the evolution of the polar magnetic
field since 1906 and use this proxy to study the role of polar flux in
the evolution of the solar cycle and the Heliospheric Magnetic Field
(HMF).
---------------------------------------------------------
Title: The Double-Ring Algorithm: A Tool for Assimilating Active
Region Data Directly into Kinematic Dynamo Models
Authors: Munoz-Jaramillo, A.; Nandi, D.; Martens, P. C.; Yeates, A. R.
2011AGUFMSH51B2009M Altcode:
The emergence of tilted bipolar active regions and the dispersal of
their flux, mediated via processes such as diffusion, differential
rotation and meridional circulation is believed to be responsible for
the reversal of the Sun's polar field. This process (commonly known as
the Babcock-Leighton mechanism) is usually modeled as a near-surface,
spatially distributed α-effect in kinematic mean-field dynamo
models. However, not only this formulation leads to a relationship
between polar field strength and meridional flow speed which is
opposite to that suggested by physical insight and predicted by
surface flux-transport simulations, but also makes it very difficult to
assimilate active region data into kinematic dynamo models. With this
in mind, we present an improved double-ring algorithm for modeling the
Babcock-Leighton mechanism based on active region eruption, within
the framework of an axisymmetric dynamo model. We demonstrate that
our treatment of the Babcock-Leighton mechanism through double-ring
eruption leads to an inverse relationship between polar field strength
and meridional flow speed as expected, reconciling the discrepancy
between surface flux-transport simulations and kinematic dynamo
models. Finally, we show how this new formulation paves the way
for applications, which were not possible before, like the direct
assimilation of active region data.
---------------------------------------------------------
Title: Bridging the Gap: Recent Improvements of Kinematic Models of
the Solar Magnetic Cycle
Authors: Munoz-Jaramillo, A.
2011AGUFMSH34B..06M Altcode:
Kinematic dynamo models are the tool par excellence for understanding
the solar magnetic cycle. During the last decade, this type of
models has seen a continuous evolution and has become increasingly
successful at reproducing solar cycle characteristics. Unfortunately,
most of ingredients that make up a kinematic dynamo model remain poorly
constrained allowing one to obtain solar-like solutions by "tuning"
the input parameters - leading to controversy regarding which parameter
set is more appropriate. In this talk we will revisit two of those
ingredients and show how to constrain them better by using theoretical
considerations. For the turbulent magnetic diffusivity - an ingredient
which attempts to capture the effect of convective turbulence on the
large scale magnetic field - we show that combining mixing-length
theory estimates with magnetic quenching allows us to obtain viable
magnetic cycles (otherwise impossible) and that the commonly used
diffusivity profiles can be understood as a spatiotemporal average of
this process. For the poloidal source - the ingredient which closes
the cycle by regenerating the poloidal magnetic field - we introduce
a more realistic way of modeling active region emergence and decay
and find that this resolves existing discrepancies between kinematic
dynamo models and surface flux transport simulations. This formulation
has made possible to study the physical mechanisms leading to the
extended minimum of cycle 23 and paves the way for future coupling
between kinematic dynamos and models of the solar corona.
---------------------------------------------------------
Title: Recent Improvements of Kinematic Models of the Solar Magnetic
Cycle
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
C. H.
2011shin.confE...3M Altcode:
One of the best tools we have for understanding the origin of
solar magnetic variability are kinematic dynamo models. During the
last decade, this type of models has seen a continuous evolution
and has become increasingly successful at reproducing solar cycle
characteristics. Unfortunately, most of ingredients that make up
a kinematic dynamo model remain poorly constrained allowing one to
obtain solar-like solutions by 'tuning' the input parameters' leading
to controversy regarding which parameter set is more appropriate. In
this poster we will revisit two of those ingredients and show how to
constrain them better by using observational data and theoretical
considerations. <P />For the turbulent magnetic diffusivity -
an ingredient which attempts to capture the effect of convective
turbulence on the large scale magnetic field - we show that combining
mixing-length theory estimates with magnetic quenching allows us
to obtain viable magnetic cycles (otherwise impossible) and that the
commonly used diffusivity profiles can be understood as a spatiotemporal
average of this process. <P />For the poloidal source - the ingredient
which closes the cycle by regenerating the poloidal magnetic field -
we introduce a more realistic way of modeling active region emergence
and decay and find that this resolves existing discrepancies between
kinematic dynamo models and surface flux transport simulations. This
formulation has made possible to study the physical mechanisms leading
to the extended minimum of cycle 23 and paves the way for future
coupling between kinematic dynamos and models of the solar corona. <P
/>This work is funded by NASA Living With a Star Grant NNX08AW53G to
Montana State University/Harvard-Smithsonian Center for Astrophysics
and the Government of India's Ramanujan Fellowship.
---------------------------------------------------------
Title: The Unusual Minimum of Solar Cycle 23: Origin and Heliospheric
Consequences
Authors: Nandi, Dibyendu; Munoz-Jaramillo, Andres; Martens, Piet C. H.
2011simi.conf....5N Altcode:
Solar cycle 23 was characterized by very weak polar magnetic field and
a large number of sunspot-less unprecedented in almost a century. This
resulted in atypical conditions in our space environment, including
low solar radiative flux, weak solar wind and heliospheric magnetic
field and record-high cosmic rays flux. Here I will review some of
these unusual conditions in space during the recently concluded solar
minimum and present the first consistent explanation of this deep
solar minimum based on dynamo simulations.
---------------------------------------------------------
Title: Meridional Surface Flows and the Recent Extended Solar Minimum
Authors: Martens, Petrus C.; Nandy, D.; Munoz-Jaramillo, A.
2011SPD....42.1705M Altcode: 2011BAAS..43S.1705M
Nandy, Munoz, & Martens, have published a kinematic dynamo model
that successfully reproduces the main characteristics of the recent
extended solar minimum (Nature 2011, 471, 80). The model depends on
the solar meridional flow and its return flow along the tachocline
determining the period and character of the cycle. In particular Nandy
et al. found that a meridional flow that is fast in the first half
of the cycle and then slows down around solar maximum, can lead to
an extended minimum with the characteristics of the recent minimum:
an extended period without sunspots and weak polar fields. <P />It has
been pointed out that the observed surface meridional flows over the
last cycle do not fit the pattern assumed by Nandy et al. Hathaway &
Rightmire (Science 2010, 327-1350) find that the meridional speed of
small magnetic surface elements observed by SoHO/MDI decreased around
solar maximum and has not yet recovered. Basu & Antia (ApJ 2010,
717, 488) find surface plasma meridional flow speeds that are lower at
solar maximum 23 than at the surrounding minima, which is different
from both Hathaway and Nandy. <P />While there is no physical reason
that solar surface flows -- both differential rotation and meridional
flow -- would vary in lockstep with flows at greater depth, as the
large radial gradients near the surface clearly indicate, and while
Nandy et al. have demonstrated that the deeper flows dominate the net
meridional mass flow, we find that there is in effect a very satisfying
agreement between the observational results of Hathaway & Rightmire,
Basu & Antia, and the model assumptions of Nandy, Munoz, &
Martens. We present an analytical model that reconciles the first two,
followed by a hydrodynamical model that demonstrates the consistency of
these observational results with the model assumptions of Nandy et al.
---------------------------------------------------------
Title: Understanding the Origin of the Extended Minimum of Sunspot
Cycle 23
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
2011SPD....42.1743M Altcode: 2011BAAS..43S.1743M
The minimum of solar cycle 23 was characterized by very weak polar
field strength and a large number of sunspot-less days that was
unprecedented in the space age. This has had significant consequences in
the heliospheric space environment in terms of record-high cosmic-ray
flux and low levels of solar irradiance - which is the primary natural
driver of the climate system. During this un-anticipated phase,
there was some speculation as to whether the solar minimum could lead
to a Maunder-like grand minimum which coincided with the Little Ice
Age. Here we present the first consistent explanation of the defining
characteristics of this unusual minimum based on variations in the
solar meridional plasma flows, and discuss how our results compare with
observations. <P />This work is funded by NASA Living With a Star Grant
NNX08AW53G to Montana State University/Harvard-Smithsonian Center for
Astrophysics and the Government of India's Ramanujan Fellowship.
---------------------------------------------------------
Title: The Double-Ring Algorithm: Reconciling Surface Flux Transport
Simulations and Kinematic Dynamo Models
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.;
Yeates, A. R.
2011SPD....42.0205M Altcode: 2011BAAS..43S.0205M
The emergence of tilted bipolar active regions and the dispersal of
their flux, mediated via processes such as diffusion, differential
rotation and meridional circulation is believed to be responsible
for the reversal of the Sun's polar field. This process (commonly
known as the Babcock-Leighton mechanism) is usually modeled as a
near-surface, spatially distributed α-effect in kinematic mean-field
dynamo models. However, this formulation leads to a relationship
between polar field strength and meridional flow speed which is
opposite to that suggested by physical insight and predicted by
surface flux-transport simulations. With this in mind, we present
an improved double-ring algorithm for modeling the Babcock-Leighton
mechanism based on active region eruption, within the framework of
an axisymmetric dynamo model. We demonstrate that our treatment of
the Babcock-Leighton mechanism through double-ring eruption leads to
an inverse relationship between polar field strength and meridional
flow speed as expected, reconciling the discrepancy between surface
flux-transport simulations and kinematic dynamo models. Finally,
we show how this new formulation paves the way for applications,
which were not possible before, like understanding the nature of the
extended minimum of sunspot cycle 23 and direct assimilation of active
region data. <P />This work is funded by NASA Living With a Star Grant
NNX08AW53G to Montana State University/Harvard-Smithsonian Center for
Astrophysics and the Government of India's Ramanujan Fellowship.
---------------------------------------------------------
Title: The unusual minimum of sunspot cycle 23 caused by meridional
plasma flow variations
Authors: Nandy, Dibyendu; Muñoz-Jaramillo, Andrés; Martens, Petrus
C. H.
2011Natur.471...80N Altcode: 2013arXiv1303.0349N
Direct observations over the past four centuries show that the number
of sunspots observed on the Sun's surface varies periodically, going
through successive maxima and minima. Following sunspot cycle 23,
the Sun went into a prolonged minimum characterized by a very weak
polar magnetic field and an unusually large number of days without
sunspots. Sunspots are strongly magnetized regions generated by a
dynamo mechanism that recreates the solar polar field mediated through
plasma flows. Here we report results from kinematic dynamo simulations
which demonstrate that a fast meridional flow in the first half of a
cycle, followed by a slower flow in the second half, reproduces both
characteristics of the minimum of sunspot cycle 23. Our model predicts
that, in general, very deep minima are associated with weak polar
fields. Sunspots govern the solar radiative energy and radio flux,
and, in conjunction with the polar field, modulate the solar wind, the
heliospheric open flux and, consequently, the cosmic ray flux at Earth.
---------------------------------------------------------
Title: Magnetic Quenching of Turbulent Diffusivity: Reconciling
Mixing-length Theory Estimates with Kinematic Dynamo Models of the
Solar Cycle
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
C. H.
2011ApJ...727L..23M Altcode: 2010arXiv1007.1262M
The turbulent magnetic diffusivity in the solar convection zone is
one of the most poorly constrained ingredients of mean-field dynamo
models. This lack of constraint has previously led to controversy
regarding the most appropriate set of parameters, as different
assumptions on the value of turbulent diffusivity lead to radically
different solar cycle predictions. Typically, the dynamo community
uses double-step diffusivity profiles characterized by low values of
diffusivity in the bulk of the convection zone. However, these low
diffusivity values are not consistent with theoretical estimates based
on mixing-length theory, which suggest much higher values for turbulent
diffusivity. To make matters worse, kinematic dynamo simulations cannot
yield sustainable magnetic cycles using these theoretical estimates. In
this work, we show that magnetic cycles become viable if we combine the
theoretically estimated diffusivity profile with magnetic quenching of
the diffusivity. Furthermore, we find that the main features of this
solution can be reproduced by a dynamo simulation using a prescribed
(kinematic) diffusivity profile that is based on the spatiotemporal
geometric average of the dynamically quenched diffusivity. This bridges
the gap between dynamically quenched and kinematic dynamo models,
supporting their usage as viable tools for understanding the solar
magnetic cycle.
---------------------------------------------------------
Title: Towards better constrained models of the solar magnetic cycle
Authors: Munoz-Jaramillo, Andres
2010PhDT.......193M Altcode:
The best tools we have for understanding the origin of solar magnetic
variability are kinematic dynamo models. During the last decade,
this type of models has seen a continuous evolution and has become
increasingly successful at reproducing solar cycle characteristics. The
basic ingredients of these models are: the solar differential rotation
-- which acts as the main source of energy for the system by shearing
the magnetic field; the meridional circulation -- which plays a crucial
role in magnetic field transport; the turbulent diffusivity -- which
attempts to capture the effect of convective turbulence on the large
scale magnetic field; and the poloidal field source -- which closes
the cycle by regenerating the poloidal magnetic field. However, most
of these ingredients remain poorly constrained which allows one to
obtain solar-like solutions by "tuning" the input parameters, leading
to controversy regarding which parameter set is more appropriate. In
this thesis we revisit each of those ingredients in an attempt to
constrain them better by using observational data and theoretical
considerations, reducing the amount of free parameters in the model. For
the meridional flow and differential rotation we use helioseismic data
to constrain free parameters and find that the differential rotation
is well determined, but the available data can only constrain the
latitudinal dependence of the meridional flow. For the turbulent
magnetic diffusivity we show that combining mixing-length theory
estimates with magnetic quenching allows us to obtain viable magnetic
cycles and that the commonly used diffusivity profiles can be understood
as a spatiotemporal average of this process. For the poloidal source
we introduce a more realistic way of modeling active region emergence
and decay and find that this resolves existing discrepancies between
kinematic dynamo models and surface flux transport simulations. We also
study the physical mechanisms behind the unusually long minimum of cycle
23 and find it to be tied to changes in the meridional flow. Finally,
by carefully constraining the system through surface magnetic field
observations, we find that what is believed to be the primary source
of poloidal field (also known as Babckock-Leigthon mechanism) may not
be enough to sustain the solar magnetic cycle.
---------------------------------------------------------
Title: A Double-ring Algorithm for Modeling Solar Active Regions:
Unifying Kinematic Dynamo Models and Surface Flux-transport
Simulations
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
C. H.; Yeates, Anthony R.
2010ApJ...720L..20M Altcode: 2010arXiv1006.4346M
The emergence of tilted bipolar active regions (ARs) and the dispersal
of their flux, mediated via processes such as diffusion, differential
rotation, and meridional circulation, is believed to be responsible
for the reversal of the Sun's polar field. This process (commonly
known as the Babcock-Leighton mechanism) is usually modeled as a
near-surface, spatially distributed α-effect in kinematic mean-field
dynamo models. However, this formulation leads to a relationship
between polar field strength and meridional flow speed which is
opposite to that suggested by physical insight and predicted by surface
flux-transport simulations. With this in mind, we present an improved
double-ring algorithm for modeling the Babcock-Leighton mechanism
based on AR eruption, within the framework of an axisymmetric dynamo
model. Using surface flux-transport simulations, we first show that an
axisymmetric formulation—which is usually invoked in kinematic dynamo
models—can reasonably approximate the surface flux dynamics. Finally,
we demonstrate that our treatment of the Babcock-Leighton mechanism
through double-ring eruption leads to an inverse relationship between
polar field strength and meridional flow speed as expected, reconciling
the discrepancy between surface flux-transport simulations and kinematic
dynamo models.
---------------------------------------------------------
Title: Towards better Constrained Kinematic Dynamo Models: Turbulent
Diffusivity and Diffusivity Quenching
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
2010AAS...21640116M Altcode:
The turbulent magnetic diffusivity in the Solar Convection Zone
(SCZ) is one of the most poorly constrained ingredients of mean-field
dynamo models. This lack of constrain has previously led to controversy
regarding which set of parameters is more appropriate (yielding better
solar like solutions) and the generation of radically different cycle
predictions. Furthermore, due to the relative freedom in the different
parameters associated with it, more often than not it is used to finely
tune the dynamo solutions. As of now, the dynamo community seems
to have settled on double step diffusivity profiles characterized
by low values of diffusivity inside most of the convection zone;
notwithstanding that these values of diffusivity are not consistent
with theoretical considerations based on mixing-length theory, which
suggest much higher values of turbulent diffusivity. To make matters
worse, standard kinematic dynamo simulations cannot yield sustainable
magnetic cycles using theoretical estimates. Here we study how magnetic
diffusivity quenching can provide a physically meaningful way out of
this discrepancy and whether standard diffusivity profiles are truly
a representation of a physical process. This work is funded by NASA
Living With a Star grant NNG05GE47G.
---------------------------------------------------------
Title: Are Active Regions as Relevant for the Solar Cycle as we Think?
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
2010AAS...21640108M Altcode: 2010BAAS...41R.858M
The long and short term variability of the Sun is strongly determined
by the evolution of the solar magnetic cycle, which is sustained
through the action of a magneto-hydrodynamic dynamo. In our current
understanding of the dynamo, the poloidal field (which acts as a
starting point for the cycle) is recreated through the emergence and
decay of active regions subjected to the collective effect of meridional
circulation and turbulent diffusion; a process commonly referred to as
the Babcock-Leighton mechanism. Dynamo models based on this mechanism
have been quite successful in reproducing the different properties of
the solar cycle and have also been used to make predictions of cycle
24. However, the question of whether the BL mechanism is enough to
sustain the solar cycle has not yet been addressed quantitatively. By
including real active region data in our state of the art kinematic
dynamo model we are able to take the first steps into answering this
question. <P />This work is funded by NASA Living With a Star grant
NNG05GE47G.
---------------------------------------------------------
Title: The Unusual Minimum of Solar Cycle 23 Explained
Authors: Nandy, Dibyendu; Munoz-Jaramillo, A.; Martens, P. C. H.
2010AAS...21631703N Altcode: 2010BAAS...41..898N
The minimum in activity between solar cycle 23 and 24 has been the
deepest in the space age, with an unusually large number of days
without sunspots and weak solar dipolar field strength. This has
had consequences for the heliosphere and planetary atmospheres -
given the weak solar wind, low solar irradiance and radio flux and
historically high values of cosmic ray flux that has characterized
this minimum epoch. The origin of this peculiar minimum has not
yet been clearly understood. Here we present the first theoretical
explanation of this deep minimum based on simulations of the solar
dynamo mechanism - which seeks to explain the origin and variability
of solar magnetic fields. Our simulations have uncovered a somewhat
surprising explanation, which however, provides a consistent solution
to both of the unusual features of this minimum; namely, the long period
when sunspots were missing and the very weak solar polar field strength.
---------------------------------------------------------
Title: Towards better constrained models of the solar magnetic cycle
Authors: Muñoz-Jaramillo, Andrés
2010PhDT.......452M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: What do Solar Kinematic Models Tell us About the Current
Minimum?
Authors: Muñoz-Jaramillo, A.; Nandy, D.; Martens, P. C.
2009AGUFMSH11A1505M Altcode:
In the last three years the sun has reached the most unusual minimum
in the space age. Although minima as long as this one have happened
several times in the past, this one has come as a surprise in contrast
with the previous four who where fairly regular. However, such an event
is a perfect opportunity to learn more about the solar cycle and the
processes that drive it. In order to understand this event we turn
to kinematic dynamo models, which are the best tool we currently have
for understanding the solar cycle. Although modelers have been aware
of the role of the different components into setting the period of the
solar cycle, little work has been done in understanding the nature of
solar minima. Can kinematic models reproduce such an event with all
it's signatures? In this study we attempt to address this question
using our state of the art kinematic dynamo model.
---------------------------------------------------------
Title: ERRATUM: "Helioseismic Data Inclusion in Solar Dynamo Models"
<A href="bib_query\?2009ApJ...698..461M">(2009, ApJ, 698, 461)</A>
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
C. H.
2009ApJ...707.1852M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Helioseismic Data Inclusion in Solar Dynamo Models
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
C. H.
2009ApJ...698..461M Altcode: 2008arXiv0811.3441M
An essential ingredient in kinematic dynamo models of the solar cycle
is the internal velocity field within the simulation domain—the
solar convection zone (SCZ). In the last decade or so, the field of
helioseismology has revolutionized our understanding of this velocity
field. In particular, the internal differential rotation of the Sun
is now fairly well constrained by helioseismic observations almost
throughout the SCZ. Helioseismology also gives us some information
about the depth dependence of the meridional circulation in the
near-surface layers of the Sun. The typical velocity inputs used in
solar dynamo models, however, continue to be an analytic fit to the
observed differential rotation profile and a theoretically constructed
meridional circulation profile that is made to match the flow speed
only at the solar surface. Here, we take the first steps toward
the use of more accurate velocity fields in solar dynamo models by
presenting methodologies for constructing differential rotation and
meridional circulation profiles that more closely conform to the best
observational constraints currently available. We also present kinematic
dynamo simulations driven by direct helioseismic measurements for
the rotation and four plausible profiles for the internal meridional
circulation—all of which are made to match the helioseismically
inferred near-surface depth dependence, but whose magnitudes are made to
vary. We discuss how the results from these dynamo simulations compare
with those that are driven by purely analytic fits to the velocity
field. Our results and analysis indicate that the latitudinal shear in
the rotation in the bulk of the SCZ plays a more important role, than
either the tachocline or surface radial shear, in the induction of the
toroidal field. We also find that it is the speed of the equatorward
counterflow in the meridional circulation right at the base of the
SCZ, and not how far into the radiative interior it penetrates, that
primarily determines the dynamo cycle period. Improved helioseismic
constraints are expected to be available from future space missions
such as the Solar Dynamics Observatory and through analysis of more
long-term continuous data sets from ground-based instruments such as
the Global Oscillation Network Group. Our analysis lays the basis for
the assimilation of these helioseismic data within dynamo models to
make future solar cycle simulations more realistic.
---------------------------------------------------------
Title: The Unusual Minimum of Cycle 23: Observations and
Interpretation
Authors: Martens, Petrus C.; Nandy, D.; Munoz-Jaramillo, A.
2009SPD....40.2403M Altcode:
The current minimum of cycle 23 is unusual in its long duration, the
very low level to which Total Solar Irradiance (TSI) has fallen, and
the small flux of the open polar fields. The deep minimum of TSI seems
to be related to an unprecedented dearth of polar faculae, and hence to
the small amount of open flux. Based upon surface flux transport models
it has been suggested that the causes of these phenomena may be an
unusually vigorous meridional flow, or even a deviation from Joy's law
resulting in smaller Joy angles than usual for emerging flux in cycle
23. There is also the possibility of a connection with the recently
inferred emergence in polar regions of bipoles that systematically
defy Hale's law. <P />Much speculation has been going on as to the
consequences of this exceptional minimum: are we entering another global
minimum, is this the end of the 80 year period of exceptionally high
solar activity, or is this just a statistical hiccup? Dynamo simulations
are underway that may help answer this question. As an aside it must
be mentioned that the current minimum of TSI puts an upper limit in the
TSI input for global climate simulations during the Maunder minimum, and
that a possible decrease in future solar activity will result in a very
small but not insignificant reduction in the pace of global warming.
---------------------------------------------------------
Title: Towards Better Constrained Solar Dynamo Models: The Velocity
Field And Turbulent Diffusivity Profiles
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
2009SPD....40.0405M Altcode:
The best tool we have for understanding the origin of solar
magnetic variability is the kinematic dynamo model. During the
last decade this type of models have seen a continuous evolution
and have become increasingly successful at reproducing solar cycle
characteristics. However, some of the key ingredients used in dynamo
models remain poorly constrained which allows one to obtain solar-like
solutions by "tuning" the input parameters. Here we present out
efforts to better constrain two of the most important ingredients of
solar dynamo models:: The internal velocity field (meridional flow and
differential rotation) and the turbulent diffusivity. To accomplish
this goal, we formulate techniques to assimilate the latest results
from helioseismology to constrain the velocity fields. We also apply
mixing length theory to the Solar Model S, in conjunction with magnetic
quenching of the turbulent diffusivity, to generate more realistic
effective turbulent diffusivity profiles for kinematic dynamo models. In
essence therefore, we try to address some of these outstanding issues in
a first-principle physics based approach, rather than an ad-hoc manner.
---------------------------------------------------------
Title: Effect of the Magnetic Quenching of the Turbulent Diffusivity
in a Mean-Field Kinematic Solar Dynamo
Authors: Muñoz-Jaramillo, A.; Nandy, D.; Martens, P. C.
2008AGUSMSP41A..09M Altcode:
The fundamental model used to study the solar dynamo mechanism is
based on the electromagnetic induction equation coupled with Ohm's
law. Apart from mean-field or other phenomenological source terms
(such as a Babcock-Leighton alpha-effect), the resultant dynamo
equation is composed of two terms: An advection and a diffusion
term. Depending on the relative importance of these two terms, the
dynamo can operate either in an advection-dominated or a diffusion
dominated regime. One of the parameters that determine which of these
regimes the dynamo operates in is the effective magnetic diffusivity,
this parameter is expected to be enhanced by convective turbulence
in stellar convection zones. The diffusivity values can range from
104 cm2/s in the radiative zone (where there is no turbulence) to
1012-14 cm2/s in the upper convection zone. The depth dependence of
this effective diffusivity is not particularly well-constrained and
most commonly used profiles involve a relatively low diffusivity in
the convection zone (1010-11 cm2/s) - which makes the dynamo operate
in the advection-dominated regime. The underlying problem here is
that these values of diffusivity are not consistent with theoretical
considerations based on mixing-length theory, which suggest much higher
values of turbulent diffusivity; this would make the dynamo operate
in a diffusion-dominated regime. However, a possible solution to this
inconsistency may be in the quenching effect that strong magnetic
fields have on turbulence. We have recently developed a kinematic solar
dynamo based on a novel numerical technique called the exponential-
propagation method. Using this model, we study magnetic diffusivity
quenching and discuss how its effect may reconcile the theoretically
suggested turbulent diffusivity values with the effective diffusivity
profiles most commonly used in this type of models.