Author name code: martens
ADS astronomy entries on 2022-09-14
author:"Martens, Petrus C.H." OR author:"Martens, Piet" 
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Title: Machine Learning-based Prediction of Solar Energetic Particle
    Events Using GOES Proton and X-ray Time Series Data.
Authors: Rotti, Sumanth; Martens, Petrus
Bibcode: 2022cosp...44.1182R
Altcode:
  Solar Energetic Particle (SEP) events are sudden enhancements in space
  around Earth's radiation environment, often associated with eruptions
  such as solar flares and coronal mass ejections (CMEs). SEPs determine
  the dosage exposure on astronauts and spacecraft equipment outside the
  Earth's magnetosphere, while proton events &gt;100MeV can penetrate
  the Earth's upper atmosphere. Hence, reliable predictions of SEPs are
  vital to mitigate space weather hazards for space travel. This work
  uses machine learning (ML) models for a binary classification problem
  addressing the prediction &gt;10 MeV SEP events from a time-series
  perspective. We developed an integrated catalog of 342 SEP events
  observed between 1986 and 2017. Furthermore, we have carefully chosen
  temporally overlapping &gt;M1.0 class flares that have NOT given rise
  to a SEP event. The balanced data set between positive and negative
  samples provides an advantage with binary classifiers by allowing the
  hyper-plane to pass through the decision boundary such that it is not
  shifted to favor one particular class. We experiment with ML models such
  as support vector machine (SVM), decision trees, and time series forest
  (TSF) classifiers to predict SEPs. We consider the X-ray and proton
  fluxes from the Geostationary Operational Environmental Satellites
  (GOES). Furthermore, we examine the correlations of these fluxes and the
  correlations that happen across all the proton channels. This strategy
  offers a new perspective in establishing predictions for geo-effective
  SEP events arising from a large flare. The motivation behind this
  work to use ML is that the models can learn and make decisions based
  on observational data and issue quicker forecasts to improve upon the
  results of the existing statistical models.

Title: Global network of cosmic ray muon detectors for terrestrial
    and space weather monitoring and climate studies
Authors: He, Xiaochun; Martens, Petrus; Sadykov, Viacheslav; Sarsour,
   Murad; Connors, Megan; Chien, Yang-Ting; Ashok, Ashwin; Perera, Unil;
   Tiwari, Chetan; Mikler, Armin
Bibcode: 2022cosp...44.1562H
Altcode:
  Driven by the advancements in particle detection technologies, in
  recent years, there has been a growing interest in using cosmic rays,
  particularly muon particles, for many practical applications - ranging
  from tomography to space and earth weather monitoring. The challenge
  in space and earth weather monitoring on a global scale using cosmic
  rays is to deploy many efficient and affordable detectors that can
  provide accurate correlations between cosmic ray flux variations and
  weather conditions. A low-cost and portable muon particle detector has
  been developed at Georgia State University (GSU) based on expertise
  accumulated while working on the sPHENIX Experiment at Brookhaven
  National Lab. The key components include three plastic scintillators
  (20cm x 20xm x 1cm) embedded with wavelength shifting fibers and a
  Raspberry PI readout. The success of this project requires international
  collaborations and partnerships, to jointly develop cosmic ray detector
  network and create a global education outreach of climate studies. In
  this talk, we will present the detector design (including simulation
  studies) and preliminary results from prototype detectors collecting
  data on GSU campus. We would also like to take this opportunity to
  share our long-term plan and solicit a broader participation in this
  project worldwide.

Title: Exploratory Analysis of Magnetic Polarity Inversion Line
    Metadata and Eruptive Characteristics of Solar Active Regions
Authors: Aydin, Berkay; Georgoulis, Manolis K.; Martens, Petrus;
   Angryk, Rafal A.; Ji, Anli; Khasayeva, Nigar
Bibcode: 2022cosp...44.3223A
Altcode:
  Magnetic polarity inversion lines (PILs) detected in solar active
  regions and features engineered from them have been recognized as
  one of the essential features for predicting key characteristics of
  explosive and eruptive instabilities, such as solar flares and coronal
  mass ejections. We have built a systematic and comprehensive dataset
  of polarity inversion lines from line-of-sight magnetograms in HMI
  Active Region Patches (HARPs) data series. Our dataset covers the
  series ranging from May 2010 to December 2021. The dataset includes
  PIL-related binary masks of rasters (i.e., thinned PIL, the region
  of polarity inversion (RoPI), and the convex hull of PIL) as well as
  time series metadata extracted from these masks. We will introduce
  this multi-modal solar dataset and present some key results of our
  first exploratory analysis. We will further highlight relationships
  between the time evolution characteristics of magnetic PILs and provide
  an empirical analysis and predictive heuristics to demonstrate the
  usefulness of multi-modal PIL data in forecasting solar flares, both
  confined and eruptive. In particular, we will show the similarities and
  differences between pre-flare series of eruptive and confined flares
  and explore the relationships between PIL characteristics and the
  cumulative flare index. While this line of work is just starting, we
  emphasize the use of machine-learning-ready datasets for both physical
  and operational purposes, from understanding the key ingredients
  of the pre-instability phase in active regions to assigning fully
  validated forecast probabilities for major solar events that largely
  shape heliospheric space weather.

Title: Integrated Geostationary Solar Energetic Particle Events
Catalog: GSEP
Authors: Rotti, Sumanth; Aydin, Berkay; Georgoulis, Manolis K.;
   Martens, Petrus C.
Bibcode: 2022arXiv220412021R
Altcode:
  We present a catalog of solar energetic particle (SEP) events covering
  solar cycles 22, 23 and 24. We correlate and integrate three existing
  catalogs based on Geostationary Operational Environmental Satellite
  (GOES) integral proton flux data. We visually verified and labeled
  each event in the catalog to provide a homogenized data set. We have
  identified a total of 341 SEP events of which 245 cross the space
  weather prediction center (SWPC) threshold of a significant proton
  event. The metadata consists of physical parameters and observables
  concerning the possible source solar eruptions, namely flares and
  coronal mass ejections for each event. The sliced time series data
  of each event, along with intensity profiles of proton fluxes in
  several energy bands, have been made publicly available. This data set
  enables researchers in machine learning (ML) and statistical analysis
  to understand the SEPs and the source eruption characteristics useful
  for space weather prediction.

Title: Revisiting the Solar Research Cyberinfrastructure Needs:
    A White Paper of Findings and Recommendations
Authors: Nita, Gelu; Ahmadzadeh, Azim; Criscuoli, Serena;
   Davey, Alisdair; Gary, Dale; Georgoulis, Manolis; Hurlburt, Neal;
   Kitiashvili, Irina; Kempton, Dustin; Kosovichev, Alexander; Martens,
   Piet; McGranaghan, Ryan; Oria, Vincent; Reardon, Kevin; Sadykov,
   Viacheslav; Timmons, Ryan; Wang, Haimin; Wang, Jason T. L.
Bibcode: 2022arXiv220309544N
Altcode:
  Solar and Heliosphere physics are areas of remarkable data-driven
  discoveries. Recent advances in high-cadence, high-resolution
  multiwavelength observations, growing amounts of data from realistic
  modeling, and operational needs for uninterrupted science-quality data
  coverage generate the demand for a solar metadata standardization and
  overall healthy data infrastructure. This white paper is prepared as
  an effort of the working group "Uniform Semantics and Syntax of Solar
  Observations and Events" created within the "Towards Integration of
  Heliophysics Data, Modeling, and Analysis Tools" EarthCube Research
  Coordination Network (@HDMIEC RCN), with primary objectives to discuss
  current advances and identify future needs for the solar research
  cyberinfrastructure. The white paper summarizes presentations and
  discussions held during the special working group session at the
  EarthCube Annual Meeting on June 19th, 2020, as well as community
  contribution gathered during a series of preceding workshops and
  subsequent RCN working group sessions. The authors provide examples
  of the current standing of the solar research cyberinfrastructure, and
  describe the problems related to current data handling approaches. The
  list of the top-level recommendations agreed by the authors of the
  current white paper is presented at the beginning of the paper.

Title: Filament Chirality Detection using Machine Learning
Authors: Venkataramanasastry, Aparna; Rotti, Sumanth; Martens, Petrus
Bibcode: 2021AGUFMSH55A1821V
Altcode:
  Space weather monitoring and prediction efforts are growing in
  importance with the increasing interest in commercialization of the
  space sector and as it opens space for public. From our previous
  analysis (Aparna &amp; Martens, 2020) of about 2 solar cycles of
  CME and ICME data we have shown that the CME Bz can be predicted by
  monitoring the regions of eruptions or the chromospheric filaments on
  the Sun. This analysis requires manual identification of chirality
  in the cases of filament eruptions and the skew of the overlying
  arcade fields in active regions where filaments might not be visible
  or may not be fully formed. Once the chirality is obtained, we get
  the axial field direction of the polarity inversion line of that
  region using photospheric magnetograms. Hence, so far, we have been
  manually determining the chiralities of these filaments. Due to the
  potential of this method in determining a non-geo-effective CME from
  a geo-effective one while a filament is still on the Sun, further
  efforts in automating the process seems worthwhile. As a first step,
  we automate the filament chirality identification using computer
  vision. We use chromospheric filament data between 2003 and 2013 from
  Helio Research, Inc., run by Mrs. Sara Martin - one of the pioneers in
  filament chirality and filament eruptions research, taken in the center
  line of Halpha and its red and blue wings. The images have a resolution
  of 0.9 per pixel with a narrow field of view. We use LabelBox1, a
  proprietary online tool to label the various features in the images
  and Google Cloud2 for storing and easy access to our images. We will
  present the details of the machine learning algorithm that we use for
  classifying the images and the results from our model at the AGU 2021
  Fall meeting. References Aparna, V., &amp; Martens, P. C. H., 2020ApJ,
  897, 68 1https://labelbox.com 2https://cloud.google.com/edu/

Title: Prediction of Solar Energetic Particle Events Based on GOES
    Proton, Electron and X-ray Fluxes Time Series Data Using Machine
    Learning Techniques.
Authors: Rotti, Sumanth; Martens, Petrus
Bibcode: 2021AGUFMSH15B2036R
Altcode:
  Solar Energetic Particle (SEP) event is a sudden enhancement in space
  around Earth's radiation environment that is often associated with
  solar eruptions such as flares and coronal mass ejections (CMEs). SEPs
  determine the dosage exposure on astronauts and spacecraft equipment
  outside the Earth's magnetosphere, while proton events &gt;100MeV can
  penetrate the Earth's upper atmosphere. Hence, reliable predictions
  of SEPs are vital to mitigate space weather hazards for space
  travel. In this work, we address the prediction &gt;10 MeV SEP
  events from a multivariate time series perspective using machine
  learning (ML) models. Between 1997 and 2020, we have identified 348
  SEP events using available catalogs. Furthermore, we have carefully
  chosen 348 temporally overlapping &gt;M1.0 class flares that have
  NOT given rise to a SEP event. Here, we experiment with ML models
  such as support vector machine (SVM) and time series forest (TSF)
  classifiers to predict SEPs under a binary classification problem
  domain. We consider the X-ray, electron, and proton fluxes from the
  Geostationary Operational Environmental Satellites (GOES). Furthermore,
  we examine the correlations of these fluxes and the correlations that
  happen across all the proton and electron channels. This strategy
  offers a new perspective in establishing predictions for geo-effective
  SEP events arising from a large flare. Also, the balanced data set
  between positive and negative samples gives an advantage to binary
  classifiers by allowing the hyper-plane to pass through the decision
  boundary such that it is not shifted to favor one particular class. The
  motivation behind this work to use ML is that the models can learn and
  make decisions based on observational data and issue quicker forecasts
  to improve upon the results of the existing statistical models.

Title: New initiatives from the Solar Data Analysis Center
Authors: Ireland, Jack; Amezcua, Arthur; Davey, Alisdair; Inglis,
   Andrew; Mansky, Edmund; Martens, Petrus; Oien, Niles; Spencer,
   Jennifer; Yashiro, Seiji
Bibcode: 2021AGUFMSH55A1823I
Altcode:
  We describe new initiatives undertaken by the Solar Data Analysis Center
  (SDAC) to better support the solar physics community. The role of the
  SDAC is to support the scientific analysis of solar physics data. The
  SDAC has begun a new effort to catalog solar physics data resources from
  around the web. The purpose of this effort is to more fully understand
  the breadth of solar physics data that are available, to provide a
  place where users from solar physics and other disciplines can search
  a curated catalog of data resources, and to inform the development of
  new SDAC capabilities that are aligned with NASA's Heliophysics Digital
  Resource Library initiative. Resources that are in scope include solar
  physics data from NASA (and non-NASA) supported missions and instruments
  (both current and historical), rocket and balloon experiments, cubesats
  and smallsats, and ground based instruments and facilities (for example,
  eclipse observations). Also in scope are online resources that describe
  solar features and events (for example, the HEK and the CDAW list
  of CMEs), and solar physics related data products which are not the
  primary data products of NASA solar physics missions/instruments:
  for example, the Helioviewer JPEG2000 image files and machine learning
  ready datasets fall in to this category. Another new initiative under
  development is the regular testing of the command-line Virtual Solar
  Observatory (VSO) clients. We are developing a VSO testing capability
  that performs automated data searches using the same SunPy, Solarsoft
  and VSO code that the solar physics community uses on a daily basis. The
  purpose of this testing capability is to capture important diagnostic
  information of the data search and download functionality of the VSO,
  SunPy and Solarsoft. This information will be used to improve the VSO,
  SunPy and Solarsoft. Finally, we describe some recent updates to the
  capabilities of the VSO, including newly available datasets.

Title: Solar evolution and extrema: current state of understanding
    of long-term solar variability and its planetary impacts
Authors: Nandy, Dibyendu; Martens, Petrus C. H.; Obridko, Vladimir;
   Dash, Soumyaranjan; Georgieva, Katya
Bibcode: 2021PEPS....8...40N
Altcode:
  The activity of stars such as the Sun varies over timescales
  ranging from the very short to the very long—stellar and planetary
  evolutionary timescales. Experience from our solar system indicates that
  short-term, transient events such as stellar flares and coronal mass
  ejections create hazardous space environmental conditions that impact
  Earth-orbiting satellites and planetary atmospheres. Extreme events
  such as stellar superflares may play a role in atmospheric mass loss
  and create conditions unsuitable for life. Slower, long-term evolutions
  of the activity of Sun-like stars over millennia to billions of years
  result in variations in stellar wind properties, radiation flux, cosmic
  ray flux, and frequency of magnetic storms. This coupled evolution of
  star-planet systems eventually determines planetary and exoplanetary
  habitability. The Solar Evolution and Extrema (SEE) initiative of the
  Variability of the Sun and Its Terrestrial Impact (VarSITI) program of
  the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) aimed
  to facilitate and build capacity in this interdisciplinary subject
  of broad interest in astronomy and astrophysics. In this review, we
  highlight progress in the major themes that were the focus of this
  interdisciplinary program, namely, reconstructing and understanding
  past solar activity including grand minima and maxima, facilitating
  physical dynamo-model-based predictions of future solar activity,
  understanding the evolution of solar activity over Earth's history
  including the faint young Sun paradox, and exploring solar-stellar
  connections with the goal of illuminating the extreme range of activity
  that our parent star—the Sun—may have displayed in the past,
  or may be capable of unleashing in the future.

Title: Which Verification Metrics Are Appropriate for Rare-Event
    Classification Problems?
Authors: Ahmadzadeh, Azim; Kempton, Dustin; Martens, Petrus; Angryk,
   Rafal
Bibcode: 2021AGUFMSH53A..05A
Altcode:
  Strong solar flares are indeed rare events, which make the
  flare classification task a rare-event problem. Solar energetic
  particle events are even rarer space weather events as only a few
  instances of them are recorded each year. With the unprecedented
  growth in employment of Machine Learning algorithms for rare-event
  classification/forecast problems, a proper evaluation of rare-event
  models becomes a necessary skill for domain experts to have. This task
  remains to be an outstanding challenge as both the learning process and
  the metrics used for quantitative verification of models can easily
  obscure or skew the true performance of models and yield misleading
  and biased results. To help mitigate this effect we introduce a
  bounded semimetric space that provides a generic representation for
  any deterministic performance verification metric. This space, named
  Contingency Space, can be easily visualized and shed light on models
  performance as well as on the metrics distinct behavior. An arbitrary
  models performance can be mapped to a unique point in this space,
  which allows comparison of multiple models at the same time, for a given
  metric. Using this geometrical setting we show the difference between a
  metrics interpretation of performance and the true performance of the
  model. Using this perspective, models which are seemingly different
  but practically identical, or only marginally different, can be easily
  spotted. By tracking down a learners performance at each epoch, we
  can also compare different learners learning paths, which provides a
  deeper understanding of the utilized algorithms and their challenge
  in the learning process. Moreover, in the Contingency Space, a given
  verification metric can be represented by a geometrical surface,
  which allows a visual comparison between different metrics---a task
  that without this concept could be done only by the tedious algebraic
  comparison of metrics formulae. Moreover, using such a surface,
  for the first time we can see and quantify the impact of scarcity
  of data (intrinsic to rare-even problems) on different metrics. This
  extra knowledge provides us with the information we need to choose an
  appropriate metric for evaluation of our rare-event models.

Title: Using CME Progenitors to Assess CME Geoeffectiveness
Authors: Mundra, Kashvi; Aparna, V.; Martens, Petrus
Bibcode: 2021ApJS..257...33M
Altcode: 2020arXiv201102123M
  There have been a few previous studies claiming that the effects of
  geomagnetic storms strongly depend on the orientation of the magnetic
  cloud portion of coronal mass ejections (CMEs). Aparna &amp; Martens,
  using halo-CME data from 2007 to 2017, showed that the magnetic field
  orientation of filaments at the location where CMEs originate on the
  Sun can be used to credibly predict the geoeffectiveness of the CMEs
  being studied. The purpose of this study is to extend their survey
  by analyzing the halo-CME data for 1996-2006. The correlation of
  filament axial direction on the solar surface and the corresponding
  Bz signatures at L1 are used to form a more extensive analysis
  for the results previously presented by Aparna &amp; Martens. This
  study utilizes Solar and Heliospheric Observatory Extreme-ultraviolet
  Imaging Telescope 195 Å, Michelson Doppler Imager magnetogram images,
  and Kanzelhöhe Solar Observatory and Big Bear Solar Observatory
  Hα images for each particular time period, along with ACE data for
  interplanetary magnetic field signatures. Utilizing all these, we
  have found that the trend in Aparna &amp; Martens' study of a high
  likelihood of correlation between the axial field direction on the
  solar surface and Bz orientation persists for the data between 1996
  and 2006, for which we find a match percentage of 65&amp;percnt;.

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.
Bibcode: 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.

Title: Updates To The Virtual Solar Observatory
Authors: Ireland, J.; Amezcua, A.; Davey, A.; Hourcle, J.; Mansky,
   E.; Martens, P.; Oien, N.; Spencer, J.
Bibcode: 2021AAS...23821302I
Altcode:
  The Virtual Solar Observatory (VSO) is a community-driven tool that
  allows users to seamlessly search for data from multiple, geographically
  distributed solar data providers. In this presentation we will describe
  the latest updates to the VSO, including newly available data sets,
  and the adoption and use of REST (REpresentational State Transfer)
  and TAP (Table Access Protocol) methods that expand the reach of the
  VSO. We will also describe the VSO's support for data providers written
  in Python, and the VSO's interaction with the SunPy Project to bring
  access to solar data via a SunPy VSO client. Finally, we will briefly
  outline how the VSO will contribute to NASA's Heliophysics Digital
  Resource Library.

Title: Data Benchmarking for Solar Flare, CME and SEP Event
Forecasting: Different Prediction and Verification Needs, Unified
Authors: Georgoulis, Manolis K.; Martens, Petrus; Aydin, Berkay;
   Ahmadzadeh, Azim; Kempton, Dustin J.; Angryk, Rafal A.
Bibcode: 2021cosp...43E2357G
Altcode:
  In this synergistic, interdisciplinary work we convey two principles
  that we consider central to improving space weather forecast
  capabilities of current and future modeling efforts: first, that
  data, model and performance verification tasks are equally important
  and should be treated on equal footing. Second, that the solar end
  of adverse space weather, comprising flares, coronal mass ejections
  (CMEs) and Solar Energetic Particle (SEP) events should be viewed and
  treated as a single, albeit multi-faceted, physical problem, rather
  than as a set of standalone problems corresponding to each facet. We
  present paradigms for both of these principles: first, we discuss a
  solar flare benchmark dataset in which the data are fully verified
  and we have taken steps to verify different forecast models and their
  performance. We show that unverified models lead to much degraded
  performance. Second, we outline the main aspects of a methodology to
  forecast SEP events in terms of temporal profile and peak proton flux
  starting from forecasting their source eruptions in the Sun. Performance
  needs dictate the introduction of two modeling tiers, one for eruption
  forecasting and projected SEP properties and another for updated,
  forecast SEP properties in case of SEP-eligible eruptions. This practice
  enables a dual validation of the performance for both tiers, at the
  same time constraining applicable uncertainties that could otherwise
  render the overall task untenable. Benefits of this approach in terms
  of both operations-to-research and research-to-operations are profound
  and can lead to both an improved physical understanding of vast swaths
  of the heliosphere, along with future prediction services combining
  computational efficiency with proven, quantifiable value.

Title: Filament Bz and IMF Bz - A Relation
Authors: Venkataramanasastry, Aparna; Martens, Petrus
Bibcode: 2021cosp...43E1046V
Altcode:
  An ICME (interplanetary coronal mass ejection) magnetic field
  orientation plays an important role in determining if it will cause
  a geo-magnetic storm upon impact with the Earth's magnetosphere. A
  southward pointing filament field at the CME causes the maximum
  impact geomagnetic storms on Earth and potentially damage power grids,
  satellites and astronauts in space. We conduct a survey using halo-CMEs
  from 2007-2017 to observe the correlation between the direction of the
  axial magnetic field of the source region on the Sun and the enhancement
  in the interplanetary magnetic field (IMF) near the Earth from these
  CMEs. We see a significant correlation between the direction of the
  axial field of the filament and that of the IMF near Earth. We find
  that about 86% of the times the magnetic field orientation of a CME is
  retained after the eruption. We conclude that this method can be used
  for effectively predicting space weather related events. The above
  analysis involves visually determining filament chirality to obtain
  the axial field direction. We investigate this further with vector
  magnetograms of the source regions to determine if they give the same
  field orientation as that obtained using chirality. This will further
  confirm the chirality method and is also useful for automating space
  weather predictions. At the Earth we use flux rope fitting techniques to
  get the exact orientation of the IMF. Vector magnetograms from SDO/HMI
  are used for obtaining the axial magnetic field of filaments for a
  subset (from 2010-2017) of the data used in the previous study which
  ranged from 2007-2017. ACE data is used for understanding the IMF at L1.

Title: Coronal Sigmoids and Chromospheric Filaments - A relation?
Authors: Venkataramanasastry, Aparna; Georgoulis, Manolis K.;
   Martens, Petrus
Bibcode: 2021cosp...43E1765V
Altcode:
  Sigmoids are forward (S-shaped) or inverse (Z-shaped) features
  on the Sun that are seen at coronal heights in X-ray or high
  temperature extreme ultraviolet (EUV) wavelengths. The sharpest
  and brightest of them are highly eruptive. They usually deform or
  disappear via coronal mass ejections. This makes it important to
  understand X-ray sigmoids because of their relevance for space-weather
  forecasting purposes. Chromospheric filaments are generally observed
  as absorption features in H$\alpha$ wavelengths. In this work, we
  observe chromospheric filaments lying under the sigmoids in order to
  correlate the chiralities of the two features. We expect that if the
  formation mechanisms of filaments and sigmoids are similar then they
  should have same chirality. We have conducted a joint survey of the
  sigmoids and the underlying filaments between 2007 and 2017. We use
  Hinode soft and hard X-ray data for sigmoid images and GONG H$\alpha$
  data for the filaments. We find a total of 84 sigmoids with filaments
  within the said time period. Among these we have 41 forward and
  43 inverse sigmoids. In the 41 forward sigmoids, 8 (20%) filaments
  are dextral, 21 (50%) are sinistral and 12 (30%) ambiguous. In the
  inverse sigmoids, 16 filaments (37%) are dextral, 13 (30%) sinistral
  and 14 (33%) ambiguous. It is evident from this analysis that there
  is no clear correspondence between filament chirality and the sigmoid
  handedness. This result warrants further investigation. We therefore
  perform calculations of magnetic helicity in the photospheric regions
  that encloses the footprints of sigmoids and filaments to primarily
  obtain the sign of their helicities. For many of the cases mentioned
  above, we use SHARP (Space-weather HMI Active Region Patch) vector
  magnetograms to serve as the photospheric boundary condition to which we
  apply the linear force-free magnetic helicity and energy formulations
  of Georgoulis \&amp; LaBonte (2007). We will report on the findings
  of this study during the 43rd COSPAR General Assembly. References
  Georgoulis, M. K. \&amp; LaBonte, B. J., ApJ, 2007, 671, 1034

Title: A Catalog of Solar Flare Events Observed by the SOHO/EIT
Authors: Rotti, Sumanth A.; Martens, Petrus C. H.; Aydin, Berkay
Bibcode: 2020ApJS..249...20R
Altcode: 2020arXiv200705586R
  We have compiled a catalog of solar flares (SFs) as observed by the
  Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and
  Heliospheric Observatory (SOHO) spacecraft and the Geostationary
  Operational Environmental Satellites (GOES) spacecraft over a span
  from 1997 to 2010. During mid-1998, the cadence of EIT images was
  revised from two images per day to 12 minutes. However, the low temporal
  resolution causes significant data gaps in capturing much of the flaring
  phenomenon. Therefore, we monitor possible errors in flare detection by
  flare parameters such as temporal overlap, observational wavelength,
  and considering full field-of-view images. We consider the GOES flare
  catalog as the primary source. We describe the technique used to enhance
  the GOES detected flares using the extreme ultraviolet image captured
  by the EIT telescope. In order to detect brightenings, we subtract
  the images with a maximum cadence of 25 minutes. We have downloaded
  and analyzed the EIT data via the Virtual Solar Observatory. This flare
  data set from the SOHO/EIT period proves indispensable to the process of
  the SF predictions as the instrument has covered most of Solar Cycle 23.

Title: Solar Filaments and Interplanetary Magnetic Field B<SUB>z</SUB>
Authors: Aparna, V.; Martens, Petrus C.
Bibcode: 2020ApJ...897...68A
Altcode:
  The direction of the axis of an interplanetary coronal mass ejection
  (ICME) plays an important role in determining if it will cause a
  geomagnetic disturbance in the Earth's magnetosphere upon impact. Long
  period southward-pointing ICME fields are known to cause significant
  space weather impacts and thus geomagnetic storms. We present an
  extensive analysis of CME-ICME directionality using 86 halo-CMEs
  observed between 2007 and 2017 to compare the direction of the source
  filament axial magnetic field on the Sun and the direction of the
  interplanetary magnetic field near the Earth at the L1 Lagrangian
  point. Excluding 12 cases that were too ambiguous to determine,
  for the remaining 74 ICMEs, we find an agreement in terms of the
  northward/southward orientation of B<SUB>z</SUB> between ICMEs and
  their CME source regions in 85% of cases. Some of the previous studies
  discussed here have obtained an agreement of 77% and 55%. We therefore
  suggest that our method can be meaningful as a first step in efficiently
  predicting geoeffective ICMEs by observing and analyzing the source
  regions of CMEs on the Sun.

Title: Machine Learning in Heliophysics and Space Weather Forecasting:
    A White Paper of Findings and Recommendations
Authors: Nita, Gelu; Georgoulis, Manolis; Kitiashvili, Irina; Sadykov,
   Viacheslav; Camporeale, Enrico; Kosovichev, Alexander; Wang, Haimin;
   Oria, Vincent; Wang, Jason; Angryk, Rafal; Aydin, Berkay; Ahmadzadeh,
   Azim; Bai, Xiaoli; Bastian, Timothy; Filali Boubrahimi, Soukaina; Chen,
   Bin; Davey, Alisdair; Fereira, Sheldon; Fleishman, Gregory; Gary, Dale;
   Gerrard, Andrew; Hellbourg, Gregory; Herbert, Katherine; Ireland,
   Jack; Illarionov, Egor; Kuroda, Natsuha; Li, Qin; Liu, Chang; Liu,
   Yuexin; Kim, Hyomin; Kempton, Dustin; Ma, Ruizhe; Martens, Petrus;
   McGranaghan, Ryan; Semones, Edward; Stefan, John; Stejko, Andrey;
   Collado-Vega, Yaireska; Wang, Meiqi; Xu, Yan; Yu, Sijie
Bibcode: 2020arXiv200612224N
Altcode:
  The authors of this white paper met on 16-17 January 2020 at the New
  Jersey Institute of Technology, Newark, NJ, for a 2-day workshop that
  brought together a group of heliophysicists, data providers, expert
  modelers, and computer/data scientists. Their objective was to discuss
  critical developments and prospects of the application of machine and/or
  deep learning techniques for data analysis, modeling and forecasting
  in Heliophysics, and to shape a strategy for further developments in
  the field. The workshop combined a set of plenary sessions featuring
  invited introductory talks interleaved with a set of open discussion
  sessions. The outcome of the discussion is encapsulated in this white
  paper that also features a top-level list of recommendations agreed
  by participants.

Title: Multivariate time series dataset for space weather data
    analytics
Authors: Angryk, Rafal A.; Martens, Petrus C.; Aydin, Berkay; Kempton,
   Dustin; Mahajan, Sushant S.; Basodi, Sunitha; Ahmadzadeh, Azim; Cai,
   Xumin; Filali Boubrahimi, Soukaina; Hamdi, Shah Muhammad; Schuh,
   Michael A.; Georgoulis, Manolis K.
Bibcode: 2020NatSD...7..227A
Altcode:
  We introduce and make openly accessible a comprehensive, multivariate
  time series (MVTS) dataset extracted from solar photospheric vector
  magnetograms in Spaceweather HMI Active Region Patch (SHARP) series. Our
  dataset also includes a cross-checked NOAA solar flare catalog that
  immediately facilitates solar flare prediction efforts. We discuss
  methods used for data collection, cleaning and pre-processing of the
  solar active region and flare data, and we further describe a novel
  data integration and sampling methodology. Our dataset covers 4,098
  MVTS data collections from active regions occurring between May 2010 and
  December 2018, includes 51 flare-predictive parameters, and integrates
  over 10,000 flare reports. Potential directions toward expansion of the
  time series, either "horizontally" - by adding more prediction-specific
  parameters, or "vertically" - by generalizing flare into integrated
  solar eruption prediction, are also explained. The immediate tasks
  enabled by the disseminated dataset include: optimization of solar flare
  prediction and detailed investigation for elusive flare predictors or
  precursors, with both operational (research-to-operations), and basic
  research (operations-to-research) benefits potentially following in
  the future.

Title: Forecasting Space Weather Hazards for Astronauts in Deep Space
Authors: Martens, P. C.; Filali Boubrahimi, S.; Aydin, B.; Angryk, R.
Bibcode: 2019AGUFMSH34B..08M
Altcode:
  Astronauts on interplanetary missions, often far off from the Earth-Sun
  line, will be subject to high energy solar energetic particle (SEP)
  events from solar eruptive flares. Protective measures can be taken
  but they require alerts of tens of minutes ahead, longer in case of
  extravehicular or off-base activities. <P />We have developed a SEP
  early warning algorithm based on data from the GOES instruments alone
  (Filali-Boubrahimi et al. 2018). Applied to the same original SEP events
  as UMASEP, developed by Núñez (2015) we get slightly better results,
  using the Decision Tree classifier. <P />We have now extended the
  training, testing, and verification database to all GOES observed SEP
  events in cycles 23 and 24, complemented with a similar sized database
  of non-SEP events, during minor flares and flare-quiet intervals. We
  are testing these data with a variety of classifiers, such as Support
  Vector Machines, Dynamic Time Warping, and Neural Networks, to find
  the best possible predictor for the largest possible (but still small)
  benchmark data set. <P />We will present the results focusing on the
  accuracy of forecasts and further data that are needed to improve
  the forecasts to the level that is required for interplanetary manned
  flight. <P />This research is supported by the NASA Space Radiation
  Analysis Group at JSC. <P />Núñez, M. 2015, Space Weather, 13,
  807-819, doi:10.1002/2015SW001256. <P />Soukaina Filali Boubrahimi,
  Berkay Aydin, Petrus Martens, and Rafal Angryk, 2018, IEEE International
  Conference on Big Data, pp. 2533-2542, https://arxiv.org/pdf/1712.01402.

Title: The SOHO/EIT solar flare catalog
Authors: Rotti, S.; Martens, P. C.
Bibcode: 2019AGUFMSH31E3341R
Altcode:
  In this work, we attempt to produce a database of solar flares
  detected by the Extreme ultraviolet Imaging Telescope (EIT) aboard
  the Solar and Heliospheric Observatory (SOHO) in accordance to
  the Geostationary Operational Environmental Satellite (GOES) flare
  catalog. The flare detection effort for the pre-SDO (Solar Dynamics
  Observatory) era available is only the GOES catalog with spatial and
  temporal specifications along with an associated active region (AR)
  number. The GOES system records flares through hard X-ray detectors and
  provides flare location on the Sun using it's SXI (Solar X-ray Imager)
  instrument (Bornmann et al., 1996). However, many flare locations
  and/or AR numbers are unavailable in the GOES catalog. For machine
  learning purposes, it is crucial to establish the correct locations
  of solar flares in the GOES catalog with other space-borne instruments
  (Aydin et al., 2019). Hence we choose the duration of EIT operations,
  i.e., from 1996 to 2010, for analysis of an extensive data set from
  the instrument. <P />Considering the GOES flare catalog as the primary
  source, the recorded peak time of the flare is used as a reference to
  select the closest Extreme UltraViolet (EUV) image of the Sun from EIT
  plus a consecutive one in order to detect brightenings. The follow-up
  image to the peak time could be before or after the peak depending
  on the temporally closest available. Although the cadence of EIT was
  revised from two images per day to 12 minutes in mid-1998 until 2010
  (ESA, 2017), this still causes significant data gaps in capturing much
  of the flaring phenomenon. Therefore, we monitor possible errors in
  flare detection by parameters such as temporal overlap, observational
  wavelength, maximum cadence limit of 24 minutes, and considering only
  full field of view (FOV) images. Over 12 years of EIT data has been
  downloaded via the Virtual Solar Observatory (VSO). <P />Nonetheless,
  this flare data from the SOHO/EIT period proves essential to the
  study of the solar atmosphere as the instrument has covered most of
  Solar Cycle 23. The flare catalog will be part of a machine learning
  benchmark dataset for solar flare prediction.

Title: Relationship between Chromospheric Filaments &amp; IMF Bz - II
Authors: Venkataramanasastry, Aparna; Martens, Petrus
Bibcode: 2019shin.confE..25V
Altcode:
  Space weather events such as Coronal Mass Ejections (CMEs) and Solar
  Energetic Particle Events that are Earth-bound tend to have tremendous
  impact on the power grids on Earth, astronauts and satellites in
  space. Effective ways of predicting such events even before they
  occur on the Sun are very helpful in avoiding or minimizing their
  effects. Chromospheric filaments on the Sun can be used to act
  as precursors to CMEs by utilizing the orientation of their axial
  magnetic field to predict if the CME will reconnect with the Earth’s
  magnetosphere. Aparna &amp; Martens, 2018 (Abstract link here) for SHINE
  yielded results that proved the above statement, in that the poloidal
  component of the axial field of the filament had the same directionality
  as that measured at L1 by using Bz and other plasma parameters from
  the Mag instrument aboard Advanced Composition Explorer situated at
  L1. The current study is directed towards using the direction of the
  axial magnetic field with the aid of vector magnetograms along with flux
  rope fitting techniques at L1 to obtain the orientation of the flux
  rope there. Vector magnetograms from SDO/HMI are used for obtaining
  the axial magnetic field of filaments for a subset (from 2010-2017)
  of the data used in the previous study which ranged from 2007-2017.

Title: Machine Learning in Solar Eruption Forecasting: a Scene-Setting
    Attempt
Authors: Georgoulis, Manolis K.; Martens, P. C.; Angryk, R. A.; Aydin,
   B.; Ahmadzadeh, A.
Bibcode: 2019shin.confE..89G
Altcode:
  Over the nearly three decades of space weather forecasting efforts,
  increased awareness suggests that conventional solar physics may
  not suffice to fully understand, and ultimately predict, eruptive
  solar activity, particularly the rarest trio of major flare, coronal
  mass ejection and solar energetic particle events. Both statistical
  and computer science techniques and approaches, such as machine and
  deep learning, seem apt to break ground in both pursuits, namely, in
  enhancing physical understanding and in enabling forecasts reliable
  enough to become practical. Like any promising new trend, however,
  machine and deep learning methods entail major challenges. In this
  brief account, we discuss a subset of these challenges whose efficient
  tackling can spur further progress. These major issues became evident in
  the framework of the European Union Flare Likelihood and Region Eruption
  Forecasting (FLARECAST) project on solar flare forecasting. The most
  substantial of them, that can easily mislead results, comparisons
  and interpretation, include climatology and uncertainties thereof,
  the construction of the training and test samples in machine learning
  methods and the class imbalance problem that becomes conspicuous when
  forecasting increasingly rare events. The above underline the need
  for benchmarking standards against which new methods are to be tested,
  verified and validated. We discuss a such benchmark, namely the Space
  Weather data ANalytics (SWAN) benchmark dataset for flare prediction,
  established at the Georgia State University Astroinformatics Cluster,
  that aims to tackle climatology and the construction of training and
  test samples. In addition, we show indicative, preliminary results
  of efforts tackling the class imbalance problem on the GSU SWAN flare
  prediction data.

Title: Work Done by Lorentz Force Drives Solar-Stellar Magnetic Cycles
Authors: Mahajan, Sushant Sushil; Nandy, Dibyendu; Martens, Petrus C.
Bibcode: 2019shin.confE.199M
Altcode:
  Our theoretical analysis of the equations of magnetohydrodynamics
  applied to the solar dynamo suggests that the work done by Lorentz force
  is the source of magnetic energy inside the solar convection zone. The
  action of Lorentz Force on poloidal field inside the convection zone
  is expected to leave behind signs of magnetic tension which manifest
  in the form of reduced latitudinal shear in differential rotation. We
  show that these expected signs of magnetic tension are consistent
  with the torsional oscillation profile of the Sun measured by three
  different instruments and hence can be used to locate regions inside
  the Sun where the magnetic field in sunspots originates.

Title: Hemispheric Preference and Cyclic Variation of Solar Filament
    Chirality from 2000 to 2016
Authors: Hazra, Soumitra; Mahajan, Sushant S.; Douglas, William Keith,
   Jr.; Martens, Petrus C. H.
Bibcode: 2018ApJ...865..108H
Altcode: 2017arXiv171105758H
  It is well known that solar filaments are features in the solar
  atmosphere that show a hemispheric preference in their chirality. The
  hemispheric preference is such that the dextral chirality dominates in
  the northern hemisphere while the sinistral chirality dominates in the
  southern. Determining the strength and cyclic variation of the degree
  of this hemispheric preference however, is challenging and tedious,
  and thus, needs to be automated. In this paper, we follow Dr. Pietro
  Bernasconi’s algorithm to detect filament chirality with two parallel
  channels of application. The algorithm is applied to H-alpha images
  with the “Advanced Automated Filament Detection and Characterization
  Code” and the full algorithm (including the detection of filaments
  and tracking) is explained to the human observer who determines the
  chirality of the solar filament. We have conducted this exercise on the
  data during the month of August from years 2000 to 2016 and we found
  that 83% of our visually determined filaments follow the hemispheric
  chirality preference, while 58% of automatically determined filaments
  follow it. Our visually compiled results have over 90% agreement with
  those of Pevtsov et al., yet the visually determined chiralities of
  filaments disagree with the automated determinations significantly. We
  find that the hemispheric preference remained the same between solar
  cycles 23 and 24, but the preference is very difficult to determine
  during the solar minimum of 2008-2010 primarily due to the absence
  of filaments.

Title: Roadmap for Reliable Ensemble Forecasting of the Sun-Earth
    System
Authors: Nita, Gelu; Angryk, Rafal; Aydin, Berkay; Banda, Juan;
   Bastian, Tim; Berger, Tom; Bindi, Veronica; Boucheron, Laura; Cao,
   Wenda; Christian, Eric; de Nolfo, Georgia; DeLuca, Edward; DeRosa,
   Marc; Downs, Cooper; Fleishman, Gregory; Fuentes, Olac; Gary, Dale;
   Hill, Frank; Hoeksema, Todd; Hu, Qiang; Ilie, Raluca; Ireland,
   Jack; Kamalabadi, Farzad; Korreck, Kelly; Kosovichev, Alexander;
   Lin, Jessica; Lugaz, Noe; Mannucci, Anthony; Mansour, Nagi; Martens,
   Petrus; Mays, Leila; McAteer, James; McIntosh, Scott W.; Oria, Vincent;
   Pan, David; Panesi, Marco; Pesnell, W. Dean; Pevtsov, Alexei; Pillet,
   Valentin; Rachmeler, Laurel; Ridley, Aaron; Scherliess, Ludger; Toth,
   Gabor; Velli, Marco; White, Stephen; Zhang, Jie; Zou, Shasha
Bibcode: 2018arXiv181008728N
Altcode:
  The authors of this report met on 28-30 March 2018 at the New Jersey
  Institute of Technology, Newark, New Jersey, for a 3-day workshop
  that brought together a group of data providers, expert modelers, and
  computer and data scientists, in the solar discipline. Their objective
  was to identify challenges in the path towards building an effective
  framework to achieve transformative advances in the understanding
  and forecasting of the Sun-Earth system from the upper convection
  zone of the Sun to the Earth's magnetosphere. The workshop aimed to
  develop a research roadmap that targets the scientific challenge
  of coupling observations and modeling with emerging data-science
  research to extract knowledge from the large volumes of data (observed
  and simulated) while stimulating computer science with new research
  applications. The desire among the attendees was to promote future
  trans-disciplinary collaborations and identify areas of convergence
  across disciplines. The workshop combined a set of plenary sessions
  featuring invited introductory talks and workshop progress reports,
  interleaved with a set of breakout sessions focused on specific topics
  of interest. Each breakout group generated short documents, listing
  the challenges identified during their discussions in addition to
  possible ways of attacking them collectively. These documents were
  combined into this report-wherein a list of prioritized activities
  have been collated, shared and endorsed.

Title: Data Handling and Assimilation for Solar Event Prediction
Authors: Martens, Petrus C.; Angryk, Rafal A.
Bibcode: 2018IAUS..335..344M
Altcode: 2017arXiv171201402M
  The prediction of solar flares, eruptions, and high energy particle
  storms is of great societal importance. The data mining approach
  to forecasting has been shown to be very promising. Benchmark
  datasets are a key element in the further development of data-driven
  forecasting. With one or more benchmark data sets established,
  judicious use of both the data themselves and the selection of
  prediction algorithms is key to developing a high quality and robust
  method for the prediction of geo-effective solar activity. We review
  here briefly the process of generating benchmark datasets and developing
  prediction algorithms.

Title: On the relationship between chromospheric filaments and IMF B
Authors: Venkataramanasastry, Aparna; Martens, Petrus
Bibcode: 2018shin.confE.224V
Altcode:
  I present a poster that depicts a qualitative relationship between the
  direction of the axial magnetic field of chromospheric filaments on
  the Sun and the Interplanetary Magnetic Field axis of Earth-impacting
  Coronal Mass Ejections (CMEs) that were caused due to the eruptions
  of those filaments. I conduct analysis of a set of halo CMEs between
  2007 and 2017 by comparing the axial magnetic field of CME producing
  filaments determined using their chirality. Utilizing the magnetic
  field measurements obtained from the Advanced Composition Satellite
  (ACE), the variations in the interplanetary magnetic field (IMF) due
  to the CME are analyzed. The arrival time of the CME is calculated in
  a linear fashion according to the estimated speed. To quantitatively
  establish a relation between the two, we use flux rope models to fit the
  interplanetary magnetic field. This will suggest how the orientation
  of the field is varying. In other words, obtaining the helicity at L1
  will help determine how it has changed since it was at the Sun.

Title: Scene Setting Talk: Advancing Solar Activity Forecasts Through
    Data Handling and Machine Learning
Authors: Martens, Petrus C.; Angryk, Rafal A.
Bibcode: 2018shin.confE.272M
Altcode:
  To "Advance Solar Activity Forecasts Through Observations, Data
  Assimilation and Machine Learning" solar physicists need to apply
  knowledge and experience from other domains of science, in particular
  data analytics, a subdiscipline of computer science. It is naive of
  solar physicists to think they can become experts in this field by
  simply scavenging the literature that appears pertinent. After all,
  can we expect, say a chemist, to become an expert in solar flare
  prediction by browsing the relevant literature? <P />The way to make
  progress in combining data mining and solar activity prediction is a
  close collaboration between solar physicists and data mining experts -
  unless, of course, one has the inclination to go for a second PhD in
  computer science. The latter is actually not a bad idea for students:
  we are developing a joint degree program for this purpose. <P />The
  solar-stellar informatics cluster at Georgia State University (GSU)
  is such an interdisci-plinary effort between the departments of
  Physics &amp; Astronomy and Computer Science. The first and major
  objective of this rapidly expanding group is the prediction of solar
  flares and closely related phenomena such as Solar Energetic Particles
  and Coronal Mass Ejections (CME's) using recently developed methods
  of data mining. <P />The primary requirement requirement for such
  an undertaking is developing a clean and balanced database. We are
  analyzing all available data and metadata produced during the Solar
  Dynamics Observatory (SDO) mission with the goal of developing
  a benchmark flare dataset, following the recommendation of the US
  National Science and Technology Council. <P />It is worth pointing
  out here that this undertaking is neither trivial nor effortless. SDO
  sends down of the order of 100,000 images per day, and from those
  images we produce metadata on various solar phenomena (e.g. sunspots,
  active regions, sigmoids, CME's) with automated feature recognition
  modules (Martens et al. 2012). One cannot review all these images
  and metadata by hand, so again automated methods had to be developed
  to accomplish this task. Examples of features that are not useful for
  flare prediction are sunspot or active region coordinates off the disk,
  image data gaps for various reasons (explained or unexplained), gaps
  in metadata caused for example by the relevant module being off-line,
  etc. It is obvious that any flare prediction algorithm would be greatly
  confused, say about the relation between flares and sigmoids, when
  there are undeclared gaps in either sigmoid or flare coverage. <P
  />The second step in our program is to use this benchmark data set
  to test various classifiers to see which ones perform best for solar
  flares. Here we not only use a snapshot of solar images and metadata,
  but we also look at the evolution of various parameters. Already in
  our first cursory analysis we found a strong and rather surprising
  flare parameter that I will discuss in this introduction.

Title: The solar dynamo as an interplay of rotational shear and
    magnetic field
Authors: Mahajan, Sushant Sushil; Nandy, Dibyendu; Martens, Petrus C.
Bibcode: 2018shin.confE.154M
Altcode:
  No abstract at ADS

Title: Using DSG to build the capability of space weather forecasting
    in deep space.
Authors: DeLuca, Edward; Golub, Leon; Korreck, Kelly; Savage, Sabrina
   L.; McKenzie, David E.; Rachmeler, Laurel; Winebarger, Amy R.; Martens,
   Petrus C.
Bibcode: 2018tess.conf22002D
Altcode:
  The prospect of astronaut missions to deep space and off the
  sun-earth line raises new challenges for space weather awareness
  and forecasting. Combined efforts of the science and human flight
  communities are needed to identify the requirements and identify
  pathways that will allow us to address the requirements for protecting
  human life and equipment, on a timescale consistent with the deep space
  exploration program. &lt;p class="p1" The Deep Space Gateway provides
  a platform where we can develop, test and validate a combined space
  weather instrumentation, analysis and forecasting system that can be
  used when out of routine contact with near earth based assets. This
  presentation will attempt to outline the bounds of the problem and start
  the discussion about how to build an independent space weather program.

Title: Forecasting Space Weather Hazards for Astronauts in Deep Space
Authors: Martens, P. C.
Bibcode: 2018LPICo2063.3188M
Altcode:
  Deep Space Gateway provides a unique platform to develop, calibrate,
  and test a space weather forecasting system for interplanetary travel
  in a real life setting. We will discuss requirements and design of
  such a system.

Title: Using DSG to Build the Capability of Space Weather Forecasting
    in Deep Space
Authors: DeLuca, E. E.; Golub, L.; Korreck, K.; Savage, S.; McKenzie,
   D. D.; Rachmeler, L.; Winebarger, A.; Martens, P.
Bibcode: 2018LPICo2063.3050D
Altcode:
  The prospect of astronaut missions to deep space and off the
  Sun-Earth line raises new challenges for space weather awareness and
  forecasting. We need to identify the requirements and pathways that
  will allow us to protect human life and equipment.

Title: A Two Dimensional Prediction of Solar Cycle 25
Authors: Munoz-Jaramillo, A.; Martens, P. C.
Bibcode: 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: On the Prediction of &gt;100 MeV Solar Energetic Particle
    Events Using GOES Satellite Data
Authors: Filali Boubrahimi, Soukaina; Aydin, Berkay; Martens, Petrus;
   Angryk, Rafal
Bibcode: 2017arXiv171203998F
Altcode:
  Solar energetic particles are a result of intense solar events such as
  solar flares and Coronal Mass Ejections (CMEs). These latter events all
  together can cause major disruptions to spacecraft that are in Earth's
  orbit and outside of the magnetosphere. In this work we are interested
  in establishing the necessary conditions for a major geo-effective
  solar particle storm immediately after a major flare, namely the
  existence of a direct magnetic connection. To our knowledge, this is
  the first work that explores not only the correlations of GOES X-ray
  and proton channels, but also the correlations that happen across all
  the proton channels. We found that proton channels auto-correlations
  and cross-correlations may also be precursors to the occurrence of an
  SEP event. In this paper, we tackle the problem of predicting &gt;100
  MeV SEP events from a multivariate time series perspective using easily
  interpretable decision tree models.

Title: A Survery of the Correlation between Filament Chirality and
    Sigmoid Handedness
Authors: V, A.; Hazra, S.; Martin, S. F.; Martens, P. C.
Bibcode: 2017AGUFMSH51C2498V
Altcode:
  Sigmoid regions on the Sun are often the regions that cause Coronal
  Mass Ejections (CMEs). Large CMEs most often have filaments that
  erupt with them. This study focuses on the statistical relevance of
  the shape of the sigmoid and the chirality of the filament residing in
  these sigmoids. The study further extends to the relation between the
  directionality of filaments and the Earth-directed CMEs. Sigmoid data
  from Savcheva et al. (2014) between 2007 and 2012 and a compilation of
  data using the HEK Sigmoid Sniffer (Martens et al. 2012) along with
  Hinode XRT Soft X-ray images were used for analyzing data between
  2013 and 2017. Hence this dataset consists of almost one solar cycle
  of data. A similar study done previously by Martens et al. (2013)
  analysed data for a solar cycle using an Advanced Automated Filament
  Detection &amp; Characterization Code (Bernasconi, Rust &amp; Hakim
  2005). Considering that automated chirality detection is not foolproof,
  we present this study which uses manual determination of chirality
  for accuracy using high resolution chromospheric images. Mainly full
  disk images of soft X-ray obtained from Hinode XRT (X-Ray Telescope)
  have been used to find and ensure the S or Z shape of sigmoids. H-alpha
  images obtained from BBSO and Kanzelhohe Solar Observatory (KSO) are
  used in determining the chirality of filaments. The resolutions of BBSO
  and KSO data are 1k and 4k respectively. A comparison of the analysis of
  the chirality of filaments using both data will be presented. Although
  KSO gives a 4k resolution, it is still difficult to determine the
  chirality of small filaments. For this reason, high resolution images of
  H-alpha chromospheric filaments obtained from Helio Research and Solar
  Observing Optical Network (SOON) have been used for further analysis
  of chirality of those filaments that were undeterminable using the
  BBSO or KSO full disk images. The results of the comparison using
  the different resolutions are shown. The results of the correlation
  between sigmoid shape and filament chirality are also shown. Further,
  these results are used in determining the correlation with Earth
  directed CMEs and those that cause geo-magnetic storms. Savacheva,
  A. S., McKillop, S. C., McCauley, P. I., et al., 2014, 289Bernasconi,
  P. N., Rust, D. M., &amp; Hakim, D., 2005, Sol. Phys., 228, 97 Martens,
  P., Yeates, A., &amp; Pillai, K., 2013, IAU, 3000

Title: The Faint Young Sun and Faint Young Stars Paradox
Authors: Martens, Petrus C.
Bibcode: 2017IAUS..328..350M
Altcode: 2017arXiv170601016M
  The purpose of this paper is to explore a resolution for the Faint Young
  Sun Paradox that has been mostly rejected by the community, namely the
  possibility of a somewhat more massive young Sun with a large mass loss
  rate sustained for two to three billion years. This would make the young
  Sun bright enough to keep both the terrestrial and Martian oceans from
  freezing, and thus resolve the paradox. It is found that a large and
  sustained mass loss is consistent with the well observed spin-down rate
  of Sun-like stars, and indeed may be required for it. It is concluded
  that a more massive young Sun must be considered a plausible hypothesis.

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.
Bibcode: 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: Hemispheric Preference and Cyclic Variation of Solar Filament
    Chirality
Authors: Hazra, Soumitra; Mahajan, Sushant S.; Douglas, William;
   Martens, Petrus C.
Bibcode: 2017SPD....4810617H
Altcode:
  Although the hemispheric preference of magnetic topological features in
  the solar atmosphere is a well-established fact, strength and cyclic
  variation of the hemispheric rule is a debatable issue. In this work,
  we study the chirality of 3480 solar filaments from 2000 to 2016. We
  determine the chirality of filaments manually and compare with the
  results obtained from the Advanced Automated Filament Detection
  and Characterization Code (AAFDCC). We find that 83% of our manually
  determined filaments follow the hemispheric chirality rule, while 58% of
  automatically determined filamentsfollow the same. We also compare our
  result with an other manually compiled list by Pevtsov et al. (2003). We
  find that our list matches Pevtsovs manually compiled list with 90%
  accuracy. We also find that the hemispheric chirality rule does not
  vary from cycle to cycle. However, the strength of the hemispheric
  preference decreases at the end and beginning phase of the solar cycle.

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.
Bibcode: 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.
Bibcode: 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: Solar Data Mining at Georgia State University
Authors: Angryk, R.; Martens, P. C.; Schuh, M.; Aydin, B.; Kempton,
   D.; Banda, J.; Ma, R.; Naduvil-Vadukootu, S.; Akkineni, V.; Küçük,
   A.; Filali Boubrahimi, S.; Hamdi, S. M.
Bibcode: 2016AGUFMSH11A2225A
Altcode:
  In this talk we give an overview of research projects related to solar
  data analysis that are conducted at Georgia State University. We will
  provide update on multiple advances made by our research team on
  the analysis of image parameters, spatio-temporal patterns mining,
  temporal data analysis and our experiences with big, heterogeneous
  solar data visualization, analysis, processing and storage. We will
  talk about up-to-date data mining methodologies, and their importance
  for big data-driven solar physics research.

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.
Bibcode: 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: A 2D Discrete Surface Flux Transport (DSFT) model applied to
    polar and quiet sun regions.
Authors: Eckberg, J.; Kankelborg, C. C.; Martens, P.
Bibcode: 2016AGUFMSH31B2551E
Altcode:
  We have developed a Surface Flux Transport simulation utilizing
  a Semi-Lagrangian scheme to advect discrete magnetic flux
  elements. Advection occurs due to the flow fields from supergranulation,
  meridional flow, and differential rotation. Granular advection is
  modeled using a time integrated effect which lowers the computational
  cost of the simulation. We have incorporated observational, energetic
  and geometric considerations in constructing the magnetic flux dynamics
  of emergence, interaction, and fragmentation. Our model reproduces
  observed distributions of magnetic flux in quiet sun and at the
  poles. The variation of mean squared velocities with flux is also
  reproduced. Our simulation clarifies which processes are essential in
  reproducing the dynamics of solar magnetic flux balance.

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
Bibcode: 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: 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.
Bibcode: 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: A large-scale dataset of solar event reports from automated
    feature recognition modules
Authors: Schuh, Michael A.; Angryk, Rafal A.; Martens, Petrus C.
Bibcode: 2016JSWSC...6A..22S
Altcode:
  The massive repository of images of the Sun captured by the Solar
  Dynamics Observatory (SDO) mission has ushered in the era of Big Data
  for Solar Physics. In this work, we investigate the entire public
  collection of events reported to the Heliophysics Event Knowledgebase
  (HEK) from automated solar feature recognition modules operated by
  the SDO Feature Finding Team (FFT). With the SDO mission recently
  surpassing five years of operations, and over 280,000 event reports
  for seven types of solar phenomena, we present the broadest and most
  comprehensive large-scale dataset of the SDO FFT modules to date. We
  also present numerous statistics on these modules, providing valuable
  contextual information for better understanding and validating of the
  individual event reports and the entire dataset as a whole. After
  extensive data cleaning through exploratory data analysis, we
  highlight several opportunities for knowledge discovery from data
  (KDD). Through these important prerequisite analyses presented here,
  the results of KDD from Solar Big Data will be overall more reliable
  and better understood. As the SDO mission remains operational over
  the coming years, these datasets will continue to grow in size and
  value. Future versions of this dataset will be analyzed in the general
  framework established in this work and maintained publicly online for
  easy access by the community.

Title: Heating Profiles of Coronal Loops
Authors: Plowman, Joseph; Kankelborg, Charles C.; Martens, Petrus C.
Bibcode: 2016SPD....47.0328P
Altcode:
  We analyze the temperature and density profiles of coronal
  loops, as a function of their length, using data from SDO/AIA and
  Hinode/EIS. The analysis considers the location of the heating along
  the loop's length, and we conduct a more throrough investigation of our
  previous preliminary result that heating is concentrated near the loop
  footpoints. The work now features a larger selection of coronal loops,
  compared to our previous presentations, and examines their scale-height
  temperatures to ascertain the extent to which they are hydrostatic.

Title: Observing Sun-like Stars
Authors: Martens, Petrus C.; White, Russel J.
Bibcode: 2016SPD....47.1104M
Altcode:
  The Sun represents only one realization of the many possibilities for
  stellar dynamos. In order to fully understand the physics of solar and
  stellar magnetism we need to study in full detail the magnetic cycles of
  stars that are very much like the Sun . To do this we need a telescope
  that can resolve the disks of nearby solar type stars. Georgia State's
  University Center for High Resolution Astronomy (CHARA) array is a
  diffraction limited interferometer with a baseline of over 300 m,
  located on Mount Wilson. It is the highest resolution telescope in
  the visible and infrared currently in operation. CHARA has resolved
  the disks of larger stars and observed starspots. We will describe an
  ongoing observing program for nearby Sun-like stars to determine with
  great accuracy the basic parameters of these stars and the presence of
  starspots on their surfaces. Combined with the decades long observations
  of Mount Wilson and Lowell Observatories of stellar cycles the data
  obtained will act as a powerful constraint on solar and stellar dynamo
  models and simulations.

Title: Predicting the Interplanetary Magnetic Field using Approaches
    Based on Data Mining and Physical Models
Authors: Riley, P.; Russell, C. T.; de Koning, C. A.; Biesecker, D. A.;
   Linker, J.; Owens, M. J.; Lugaz, N.; Martens, P.; Angryk, R.; Reinard,
   A.; Ulrich, R. K.; Horbury, T. S.; Pizzo, V. J.; Liu, Y.; Hoeksema, T.
Bibcode: 2015AGUFMSH14A..06R
Altcode:
  An accurate prediction of the interplanetary magnetic field, and,
  in particular, its z-component (Bz) is a crucial capability for any
  space weather forecasting system, and yet, thus far, it has remained
  largely elusive (a point exemplified by the fact that no prediction
  center currently provides a forecast for Bz). In this presentation,
  we discuss the various physical processes that can produce non-zero
  values of Bz and summarize a selection of promising approaches that may
  ultimately lead to reliable forecasts of Bz. We describe the first steps
  we have taken to develop a framework for assessing these techniques,
  and show preliminary results of their efficacy.

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.
Bibcode: 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: Solar image parameter data from the SDO: Long-term curation
    and data mining
Authors: Schuh, M. A.; Angryk, R. A.; Martens, P. C.
Bibcode: 2015A&C....13...86S
Altcode:
  The Solar Dynamics Observatory (SDO) mission captures thousands
  of images of the Sun per day, motivating the need for efficient and
  effective storage, representation, and search over a massive repository
  of data. This work investigates the general-purpose image parameter
  data produced by the SDO Feature Finding Team's trainable module, which
  operates at a fixed six minute cadence over all AIA channels. The data
  contains ten numerical measures computed for each image cell over a 64
  × 64 grid for each image. We analyze all available data and metadata
  produced over the first three years and present comprehensive statistics
  and outliers while validating the cleanliness and usability of the data
  source for future research. We then utilize a database of automated
  solar event reports to create large-scale region-labeled datasets
  available to the public. We highlight the new-found potential for
  data-driven discovery by presenting several best-case labeling scenarios
  that establish a baseline for comparing machine learning classification
  and attribute (image parameter) evaluation results. Future work focuses
  on continued dataset curation and spatiotemporal data mining.

Title: Special Section: Management, Search and Analysis of Solar
    Astronomy Big Data
Authors: Angryk, Rafal A.; Csillaghy, André; Martens, Petrus C.
Bibcode: 2015A&C....13...85A
Altcode:
  Astronomy and Computing is very proud to announce a new topical issue
  devoted to the Management, Search and Analysis of Solar Astronomy
  Big Data.

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.
Bibcode: 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.
Bibcode: 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: Exploring the Solar-stellar connection with the CHARA Array
Authors: Martens, Petrus C.; McAlister, Hal; White, Russel
Bibcode: 2015TESS....110505M
Altcode:
  It is well understood that in order to better understand solar
  magnetism it is of key importance that we have detailed data on
  magnetic activity of stars that are very much like our Sun. Georgia
  State's University Center for High Resolution Astronomy's (CHARA)
  Array is a diffraction limited interferometer with a baseline of
  over 300 m, located on Mount Wilson. CHARA has resolved the disk of
  larger early-type stars and observed starspots. It has the potential of
  detecting spots (and eclipsing exoplanets) on nearby solar-type stars,
  and thus adding significant in-depth magnetic cycle information to
  the long time series of chromospheric data from MWO and Lowell.We will
  describe the main characteristics of CHARA, highlight science results,
  and describe our plans to contribute to the renewed effort from the
  NASA Heliophysics division to study the solar-stellar connection,
  with the goal of improving long-term solar activity forecasts.URL:
  http://www.chara.gsu.edu/

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.
Bibcode: 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: First Science Results from Solar Data Mining Using Automated
    Feature Detection
Authors: Martens, P. C.
Bibcode: 2014AGUFMSH34A..07M
Altcode:
  The SDO Feature Finding Team (FFT) has produced 16 automated feature
  tracking modules for data from SDO, LASCO, and ground-based H-alpha
  observatories. The metadata produced by those modules and others are
  available from the Heliophysics Events Knowledgebase (HEK) and the
  Virtual Solar Observatory (VSO). Having metadata available for large
  amounts of events and phenomena, obtained with consistent detection
  criteria unlike catalogs produced by human observers, allows researchers
  to effectively search solar data for patterns. I will show a number
  of science results obtained recently. Not surprisingly several of the
  patterns are well known (e.g. flares occur mostly in active regions),
  but some really surprising new trends have been discovered as well,
  in at least one case upending scientific consensus. These results
  show the power and promise that systematic feature recognition and
  data mining holds for solar physics.

Title: A Comparative Evaluation of Automated Solar Filament Detection
Authors: Schuh, M. A.; Banda, J. M.; Bernasconi, P. N.; Angryk, R. A.;
   Martens, P. C. H.
Bibcode: 2014SoPh..289.2503S
Altcode: 2014SoPh..tmp...34S
  We present a comparative evaluation for automated filament detection
  in Hα solar images. By using metadata produced by the Advanced
  Automated Filament Detection and Characterization Code (AAFDCC)
  module, we adapted our trainable feature recognition (TFR) module to
  accurately detect regions in solar images containing filaments. We
  first analyze the AAFDCC module's metadata and then transform it into
  labeled datasets for machine-learning classification. Visualizations
  of data transformations and classification results are presented and
  accompanied by statistical findings. Our results confirm the reliable
  event reporting of the AAFDCC module and establishes our TFR module's
  ability to effectively detect solar filaments in Hα solar images.

Title: Feature Finding for Solar Physics
Authors: Martens, Petrus C.
Bibcode: 2014simi.conf...25M
Altcode:
  NASA's Solar Dynamics Observatory (SDO) data repository dwarfs the
  archives of all previous solar physics missions put together. The
  traditional methods of analyzing data-analyzing the images by hand -
  would simply not work and NASA tasked my Feature Finding Team (FFT)
  with developing automated feature recognition modules for solar
  phenomena likely to be observed by SDO. Having the derived metadata
  now available on-line enables to conduct statistical studies involving
  large sets of events that would be impossible now with traditional
  means. <P />First we developed some existing and new task-specific
  solar feature finding modules to be 'pipe-line' ready for the stream
  of SDO data. Secondly, we took it upon us to develop an entirely new
  'trainable' module that would be capable of identifying different types
  of solar phenomena starting from a limited number of user-provided
  examples. <P />Next I will focus on our most innovative 'trainable'
  module, developed mostly at MSU in collaboration with Prof. Angryk and
  his students at the Computer Science department there. TFirst, there
  is the strong similarity between solar and medical X-ray images with
  regard to their texture, which allowed us to apply some advances made
  in medical image recognition. Second, we found that there is a strong
  similarity between the way our trainable module works and the way our
  brain recognizes images. The brain can quickly recognize similar images
  from key characteristics, just as our code does. We conclude that our
  approach represents the beginning of a more human-like procedure for
  computer image recognition.

Title: Insights on the solar dynamo from stellar observations
Authors: Egeland, Ricky; Martens, Petrus C.; Judge, Philip G.
Bibcode: 2014AAS...22421105E
Altcode:
  A successful dynamo model should not only explain the broad
  characteristics of the magnetic field cycle for the Sun (22-year sunspot
  cycle with polarity reversals, migration of active latitudes toward
  the poles throughout the cycle, and Joy’s law), but should also be
  able to explain the cycling behavior observed in Solar-analog stars,
  which are very close to the Sun in essential characteristics. Our aim
  is to develop a set of constraints on dynamo models from the observed
  behavior of solar-analog stars obtained from a number of long-running
  synoptic surveys of cycling activity (Mount Wilson Observatory HK
  survey, Lowel Observatory Solar-Stellar Spectrograph, and the Fairborn
  Observatory Automatic Photoelectric Telescope survey), in conjuncture
  with stellar rotation and differential rotation data obtained by the
  Kepler Mission and other sources. By carefully piecing together the
  best data available today, we will provide an improved understanding
  of the parameter space in which Solar-like dynamos operate.

Title: Statistical Constraints on Joy's Law
Authors: Amouzou, Ernest C.; Munoz-Jaramillo, Andres; Martens, Petrus
   C.; DeLuca, Edward E.
Bibcode: 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.
Bibcode: 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: Hemispheric Patterns in Filament Chirality and Sigmoid Shape
    over the Solar Cycle
Authors: Martens, Petrus C.; Yeates, Anthony R.; Pillai, Karthik G.
Bibcode: 2014IAUS..300..135M
Altcode:
  The motivation for our research was to study the correlation between
  the chirality of filaments and the handedness (S- or Z-shape) of
  sigmoids. It was assumed that sigmoids would mostly coincide with
  filaments and that the S-shaped sigmoids would correlate well with
  filaments of sinistral chirality, which we found that to be at best
  a very weak relation. Since we had a full solar cycle of filament
  metadata at hand it was easy to verify the supposedly known hemispheric
  preference of filament chirality. We discovered that the hemispheric
  chirality rule was confirmed for the epoch where a thorough manual
  study had been performed, but that at other phases of the solar cycle
  the rule seems to disappear and sometimes even reverse.

Title: Helioseismic Perspective of the Solar Dynamo
Authors: Muñoz-Jaramillo, A.; Martens, P. C. H.; Nandy, D.
Bibcode: 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: Steps Toward a Large-Scale Solar Image Data Analysis to
    Differentiate Solar Phenomena
Authors: Banda, J. M.; Angryk, R. A.; Martens, P. C. H.
Bibcode: 2013SoPh..288..435B
Altcode:
  We detail the investigation of the first application of several
  dissimilarity measures for large-scale solar image data analysis. Using
  a solar-domain-specific benchmark dataset that contains multiple
  types of phenomena, we analyzed combinations of image parameters with
  different dissimilarity measures to determine the combinations that
  will allow us to differentiate between the multiple solar phenomena from
  both intra-class and inter-class perspectives, where by class we refer
  to the same types of solar phenomena. We also investigate the problem
  of reducing data dimensionality by applying multi-dimensional scaling
  to the dissimilarity matrices that we produced using the previously
  mentioned combinations. As an early investigation into dimensionality
  reduction, we investigate by applying multidimensional scaling (MDS)
  how many MDS components are needed to maintain a good representation
  of our data (in a new artificial data space) and how many can be
  discarded to enhance our querying performance. Finally, we present a
  comparative analysis of several classifiers to determine the quality
  of the dimensionality reduction achieved with this combination of
  image parameters, similarity measures, and MDS.

Title: Fast Differential Emission Measure Inversion of Solar
    Coronal Data
Authors: Plowman, Joseph; Kankelborg, Charles; Martens, Petrus
Bibcode: 2013ApJ...771....2P
Altcode: 2012arXiv1204.6306P
  We present a fast method for reconstructing differential emission
  measures (DEMs) using solar coronal data. The method consists of a
  fast, simple regularized inversion in conjunction with an iteration
  scheme for removal of residual negative emission measure. On average,
  it computes over 1000 DEMs s<SUP>-1</SUP> for a sample active region
  observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics
  Observatory, and achieves reduced chi-squared of order unity with no
  negative emission in all but a few test cases. The high performance of
  this method is especially relevant in the context of AIA, which images
  of order one million solar pixels per second. This paper describes the
  method, analyzes its fidelity, compares its performance and results with
  other DEM methods, and applies it to an active region and loop observed
  by AIA and by the Extreme-ultraviolet Imaging Spectrometer on Hinode.

Title: Filament Chirality over an Entire Cycle Determined with an
    Automated Detection Module -- a Neat Surprise!
Authors: Martens, Petrus C.; Yeates, A. R.; Mackay, D.; Pillai, K. G.
Bibcode: 2013SPD....4410104M
Altcode:
  Using metadata produced by automated solar feature detection modules
  developed for SDO (Martens et al. 2012) we have discovered some trends
  in filament chirality and filament-sigmoid relations that are new
  and in part contradict the current consensus. Automated detection
  of solar features has the advantage over manual detection of having
  the detection criteria applied consistently, and in being able to
  deal with enormous amounts of data, like the 1 Terabyte per day that
  SDO produces. Here we use the filament detection module developed by
  Bernasconi, which has metadata from 2000 on, and the sigmoid sniffer,
  which has been producing metadata from AIA 94 A images since October
  2011. The most interesting result we find is that the hemispheric
  chirality preference for filaments (dextral in the north, and v.v.),
  studied in detail for a three year period by Pevtsov et al. (2003)
  seems to disappear during parts of the decline of cycle 23 and during
  the extended solar minimum that followed. Moreover the hemispheric
  chirality rule seems to be much less pronounced during the onset
  of cycle 24. For sigmoids we find the expected correlation between
  chirality and handedness (S or Z) shape but not as strong as expected.

Title: Effects of a Meridional Flow Counter-Cell on the Solar
    Activity Cycle
Authors: Amouzou, Ernest C.; Martens, P. C.
Bibcode: 2013SPD....44..110A
Altcode:
  The effects of varying the latitudinal extent and peak flow speed of a
  simulated polar counter-cell are determined by studying the resulting
  duration and intensity of the activity cycle.

Title: Introducing the first publicly available Content-Based
    Image-Retrieval system for the Solar Dynamics Observatory mission
Authors: Michael, Schuh A.; Banda, J.; Angryk, R.; Martens, P. C.
Bibcode: 2013SPD....44...97M
Altcode:
  Since its first presentation as a demo at the 220th American
  Astronomical Society Meeting, the Solar Dynamics Observatory (SDO)
  Content-Based Image-Retrieval (CBIR) system has been open for public
  usage since December 2012. Incorporating the valuable feedback
  gathered at the AAS meeting, as well as working closely with solar
  physicists from Montana State University, this first version of our
  system provides similar image search capability for the SDO image
  data repository. In this work we present an overview of the system
  capabilities, architecture, and future improvements. We also present
  practical search examples, basic usage instructions, and some of the
  science data that can be extracted from our system. This work aims to
  gather more feedback on the system usability and functionality while
  making the community aware of a promising new tool for exploring
  SDO data.

Title: Temperature, Density, and Heating Profiles of Coronal Loops
Authors: Plowman, Joseph; Martens, P. C.; Kankelborg, C.; Ritchie,
   M.; Scott, J.; Sharma, R.
Bibcode: 2013SPD....4420106P
Altcode:
  We show detailed results of a combined DEM and density-sensitive line
  ratio analysis of coronal loops observed simultaneously by EIS and
  AIA. The temperature and density profiles of the loop are compared
  to and isolated from those of the surrounding material, and these
  properties are fit to an analytic strand heating model developed by
  Martens (2010). This research builds on our previously reported work
  by analyzing a number of coronal loops (including one observed by the
  Hi-C rocket), improved background subtraction and loop fitting. These
  improvements allow us to place significant constraints on the heating
  distribution of coronal loops.

Title: Simulating Emission of Coronal Loops with Non-Constant
    Cross-Section
Authors: Winter, Henry D.; Curme, C. D.; Reeves, K.; Martens, P. C.
Bibcode: 2013SPD....44...45W
Altcode:
  The solar corona is filled with loop-like structures that appear
  bright against the background when observed in the extreme ultraviolet
  (EUV). These loops have several remarkable properties. Warm loops
  (∼ 1 MK) appear to be ∼ 2 - 9 times as dense at their apex
  as predicted by of hydrostatic atmosphere models. These loops also
  appear to be of constant cross-section despite the fact that the field
  strength in a potential magnetic field should decrease in the corona,
  causing the loops to expand. Why many active region loops appear to be
  of constant cross-section is not well understood. Theories range from
  an internal twist of the magnetic field to observational effects. In
  this work we simulate active region loops with different expansion
  factors heated by nanoflare storms. We calculate the hydrodynamic
  properties for each loop as a function of the expansion factor
  Gamma. We show that even modest tapering ratios can lead to drastic
  changes in the density profiles of active region loops, and they can
  also explain the overpressure at the apex of these loops. Synthetic
  AIA images of each loop are made to show the observable consequences
  of the expansion of loops near the instrumental resolution. We find
  that all loops, even those with a large expansion factor, appear
  to be of near constant cross-section when images are simulated in
  AIA passbands. Only when the images are simulated for a much higher
  resolution instrument with 0.1” pixels does the real expansion
  of the loop become apparent.Abstract (2,250 Maximum Characters):
  The solar corona is filled with loop-like structures that appear
  bright against the background when observed in the extreme ultraviolet
  (EUV). These loops have several remarkable properties. Warm loops (∼
  1 MK) appear to be ∼ 2 - 9 times as dense at their apex as predicted
  by of hydrostatic atmosphere models. These loops also appear to be of
  constant cross-section despite the fact that the field strength in a
  potential magnetic field should decrease in the corona, causing the
  loops to expand. Why many active region loops appear to be of constant
  cross-section is not well understood. Theories range from an internal
  twist of the magnetic field to observational effects. In this work we
  simulate active region loops with different expansion factors heated by
  nanoflare storms. We calculate the hydrodynamic properties for each loop
  as a function of the expansion factor Gamma. We show that even modest
  tapering ratios can lead to drastic changes in the density profiles
  of active region loops, and they can also explain the overpressure at
  the apex of these loops. Synthetic AIA images of each loop are made
  to show the observable consequences of the expansion of loops near
  the instrumental resolution. We find that all loops, even those with
  a large expansion factor, appear to be of near constant cross-section
  when images are simulated in AIA passbands. Only when the images are
  simulated for a much higher resolution instrument with 0.1” pixels
  does the real expansion of the loop become apparent.

Title: Outflows and Dark Bands at Arcade-like Active Region Core
    Boundaries
Authors: Scott, J. T.; Martens, P. C. H.; Tarr, L.
Bibcode: 2013ApJ...765...82S
Altcode:
  Observations from the EUV Imaging Spectrometer (EIS) on board
  Hinode have revealed outflows and non-thermal line broadening in low
  intensity regions at the edges of active regions (ARs). We use data
  from Hinode's EIS, Solar Dynamic Observatory's Atmospheric Imaging
  Assembly and Helioseismic and Magnetic Imager, and the Transition
  Region and Coronal Explorer instrument to investigate the boundaries
  of arcade-like AR cores for NOAA ARs 11112, 10978, and 9077. A narrow,
  low intensity region that is observed at the core's periphery as a
  dark band shows outflows and increased spectral line broadening. This
  dark band is found to exist for days and appears between the bright
  coronal loop structures of different coronal topologies. We find a case
  where the dark band region is formed between the magnetic field from
  emerging flux and the field of the pre-existing flux. A magnetic field
  extrapolation indicates that this dark band is coincident with the
  spine lines or magnetic separatrices in the extrapolated field. This
  occurs over unipolar regions where the brightened coronal field is
  separated in connectivity and topology. This separation does not appear
  to be infinitesimal and an initial estimate of the minimum distance
  of separation is found to be ≈1.5-3.5 Mm.

Title: On Dimensionality Reduction for Indexing and Retrieval of
    Large-Scale Solar Image Data
Authors: Banda, J. M.; Angryk, R. A.; Martens, P. C. H.
Bibcode: 2013SoPh..283..113B
Altcode: 2012SoPh..tmp..120B
  This work investigates the applicability of several dimensionality
  reduction techniques for large-scale solar data analysis. Using a solar
  benchmark dataset that contains images of multiple types of phenomena,
  we investigate linear and nonlinear dimensionality reduction methods
  in order to reduce our storage and processing costs and maintain a
  good representation of our data in a new vector space. We present
  a comparative analysis of several dimensionality reduction methods
  and different numbers of target dimensions by utilizing different
  classifiers in order to determine the degree of data dimensionality
  reduction that can be achieved with these methods, and to discover the
  method that is the most effective for solar images. After determining
  the optimal number of dimensions, we then present preliminary results
  on indexing and retrieval of the dimensionally reduced data.

Title: Use of a time delay dynamo model to obtain solar-like sunspot
    cycles
Authors: Amouzou, E.; Nandy, D.; Muñoz-Jaramillo, A.; Martens, P.
Bibcode: 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| &gt; 3, N_D &lt; 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: The solar corona: What are the remaining fundamental physical
    questions?
Authors: Martens, Petrus C.
Bibcode: 2013ASInC..10...25M
Altcode:
  The two key unresolved physical questions in our knowledge of the
  solar corona are: (1) How is the corona heated to a temperature of
  several MK, and, directly related to that, why is the coronal emission
  structured in nearly constant cross-section loops? And, (2) what is
  the mechanism that determines the onset of solar flares and eruptions,
  and, again directly related, can flares be predicted? I will introduce
  these questions, discuss some proposed solutions that are not complete,
  and my view on getting to the full solutions.

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.
Bibcode: 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: DEMs for EIS and AIA
Authors: Plowman, J.; Kankelborg, C.; Martens, P.; Ritchie, M.; Scott,
   J.; Sharma, R.
Bibcode: 2012ASPC..456..131P
Altcode:
  We present a method for constructing Differential Emission Measures
  (DEMs) using data from solar imagers such as EIS and AIA. The method is
  simple, and very fast (∼ 1 minute per full disk AIA image). We analyze
  the fidelity of the method, and apply it to a coronal loop observed on
  April 19, 2011. The method appears to give reasonable results, although
  reconstructed DEMs can contain regions of moderately negative emission
  measure (EM). Both EIS and AIA DEM reconstructions suggest that the loop
  has a narrow temperature distribution centered at 1.2 MK, situated in a
  diffuse background of broader temperature distribution centered at 3 MK.

Title: Supporting Solar Physics Research via Data Mining
Authors: Angryk, Rafal; Banda, J.; Schuh, M.; Ganesan Pillai, K.;
   Tosun, H.; Martens, P.
Bibcode: 2012AAS...22020122A
Altcode:
  In this talk we will briefly introduce three pillars of data mining
  (i.e. frequent patterns discovery, classification, and clustering), and
  discuss some possible applications of known data mining techniques which
  can directly benefit solar physics research. In particular, we plan to
  demonstrate applicability of frequent patterns discovery methods for
  the verification of hypotheses about co-occurrence (in space and time)
  of filaments and sigmoids. We will also show how classification/machine
  learning algorithms can be utilized to verify human-created software
  modules to discover individual types of solar phenomena. Finally,
  we will discuss applicability of clustering techniques to image data
  processing.

Title: Temperature And Density Analysis Of A Coronal Loop Observed
    By Eis And Aia
Authors: Plowman, Joseph; Martens, P.; Kankelborg, C.; Ritchie, M.;
   Scott, J.; Sharma, R.
Bibcode: 2012AAS...22030905P
Altcode:
  We present a combined DEM and density-sensitive line ratio analysis of
  a loop observed simultaneously by EIS and AIA. The DEMs are calculated
  using a fast new method which we also describe. The temperature and
  density profiles of the loop are compared to and isolated from those of
  the surrounding material, and these properties are fit to an analytic
  strand heating model developed by Martens (2010). Supported by an AIA
  subcontract to Montana State University.

Title: Content-based Image Retrieval For Solar Physics: First Steps
    And A Practical Demonstration.
Authors: Banda, Juan; Angryk, R.; Martens, P.
Bibcode: 2012AAS...22020123B
Altcode:
  In this Demo/Presentation, we will introduce our open source framework
  for the creation of large-scale content-based image retrieval systems
  that is being for the NASA’s SDO mission. In this step-by-step
  presentation we will show and talk about each of the components that
  comprised our framework and describe their individual use. Before
  finishing, we will also demonstrate our demo version of the CBIR system
  that is in development for NASA’s SDO mission. Since this is an open
  tool for researchers, we will be gathering suggestions and comments
  from the participants in order to provide a more functional package
  for the solar physics community.

Title: The Virtual Solar Observatory: What Are We Up To Now?
Authors: Gurman, Joseph B.; Hill, F.; Suàrez-Solà, F.; Bogart, R.;
   Amezcua, A.; Martens, P.; Hourclé, J.; Hughitt, K.
Bibcode: 2012AAS...22020124G
Altcode:
  In the nearly ten years of a functional Virtual Solar Observatory (VSO),
  http://virtualsolar.org/, we have made it possible to query and access
  sixty-seven distinct solar data products and several event lists from
  nine spacecraft and fifteen observatories or observing networks. We
  have used existing VSO technology, and developed new software, for
  a distributed network of sites caching and serving SDO HMI and/or
  AIA data. We have also developed an application programming interface
  (API) that has enabled VSO search and data access capabilities in IDL,
  Python, and Java. <P />We also have quite a bit of work yet to do,
  including completion of the implementation of access to SDO EVE data,
  and access to some nineteen other data sets from space- and ground-based
  observatories. In addition, we have been developing a new graphic user
  interface that will enable the saving of user interface and search
  preferences. We solicit advice from the community input prioritizing
  our task list, and adding to it.

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.
Bibcode: 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| &gt; 3,ND &lt; 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: A Comparative Evaluation of Automated Solar Filament Detection
Authors: Schuh, Michael; Banda, J.; Bernasconi, P.; Angryk, R.;
   Martens, P.
Bibcode: 2012AAS...22020105S
Altcode:
  We present a comparative evaluation for automated filament detection
  in H-alpha solar images. By using metadata produced by the Advanced
  Automated Filament Detection and Characterization Code (AAFDCC)
  module, we adapted our Trainable Feature Recognition (TFR) component
  to accurately detect regions in solar images containing filaments. We
  first analyze the module's metadata and then transform it into
  labeled datasets for machine learning classification. Visualizations
  of data transformations and classification results are presented
  and accompanied by statistical findings. Our results confirm the
  reliable event reporting of the AAFDCC module as well as our ability
  to effectively detect solar filaments with our TFR component.

Title: Image Recognition and Feature Detection in Solar Physics
Authors: Martens, Petrus C.
Bibcode: 2012AAS...22032302M
Altcode:
  The Solar Dynamics Observatory (SDO) data repository will dwarf the
  archives of all previous solar physics missions put together. NASA
  recognized early on that the traditional methods of analyzing the data
  -- solar scientists and grad students in particular analyzing the images
  by hand -- would simply not work and tasked our Feature Finding Team
  (FFT) with developing automated feature recognition modules for solar
  events and phenomena likely to be observed by SDO. Having these metadata
  available on-line will enable solar scientist to conduct statistical
  studies involving large sets of events that would be impossible now
  with traditional means. <P />We have followed a two-track approach in
  our project: we have been developing some existing task-specific solar
  feature finding modules to be "pipe-line" ready for the stream of SDO
  data, plus we are designing a few new modules. Secondly, we took it
  upon us to develop an entirely new "trainable" module that would be
  capable of identifying different types of solar phenomena starting
  from a limited number of user-provided examples. Both approaches
  are now reaching fruition, and I will show examples and movies with
  results from several of our feature finding modules. <P />In the
  second part of my presentation I will focus on our “trainable”
  module, which is the most innovative in character. First, there is
  the strong similarity between solar and medical X-ray images with
  regard to their texture, which has allowed us to apply some advances
  made in medical image recognition. Second, we have found that there
  is a strong similarity between the way our trainable module works and
  the way our brain recognizes images. The brain can quickly recognize
  similar images from key characteristics, just as our code does. We
  conclude from that that our approach represents the beginning of a
  more human-like procedure for computer image recognition.

Title: Fast DEMs for EIS and AIA
Authors: Plowman, Joseph; Kankelborg, Charles; Martens, Petrus;
   Ritchie, Miriam; Scott, Jason; Sharma, Rahul
Bibcode: 2012decs.confE..77P
Altcode:
  We present a method for constructing Differential Emission Measures
  (DEMs) using data from solar imagers such as EIS and AIA. In its
  basic form, the method is very fast (approximately one minute per
  full disk AIA image), although the DEMs obtained can contain regions
  of moderately negative emission measure (EM). We demonstrate an
  extension of the method which removes regions of negative EM while
  closely matching the data. The fidelity of the method is analyzed,
  its results are compared to those of the PINTofALE MCMC DEM algorithm,
  and it is applied to a coronal loop observed on April 19, 2011.

Title: EUV Analysis of a Quasi-static Coronal Loop Structure
Authors: Scott, J. T.; Martens, P. C. H.; McKenzie, D. E.
Bibcode: 2012SoPh..276..113S
Altcode: 2011arXiv1110.5560S
  Decaying active region 10942 is investigated from 4:00 - 16:00 UT on
  24 February 2007 using a suite of EUV observing instruments. Results
  from Hinode/EIS, STEREO and TRACE show that, although the active region
  has decayed and no sunspot is present, the physical mechanisms that
  produce distinguishable loop structures, spectral line broadening,
  and plasma flows still occur. A coronal loop that appears as a
  blue-shifted structure in Doppler maps is apparent in intensity
  images of log(T)=6.0 - 6.3 ions. The loop structure is found to be
  anti-correlated with spectral line broadening generally attributed to
  non-thermal velocities. This coronal loop structure is investigated
  physically (temperature, density, geometry) and temporally. Light
  curves created from imaging instruments show brightening and dimming
  of the loop structure on two different time scales; short pulses of
  10 - 20 min and long duration dimming of two - four hours until its
  disappearance. The coronal loop structure, formed from relatively
  blue-shifted material that is anti-correlated with spectral line
  broadening, shows a density of 10<SUP>10</SUP> to 10<SUP>9.3</SUP>
  cm<SUP>−3</SUP> and is visible for longer than characteristic cooling
  times. The maximum non-thermal spectral line broadenings are found to
  be adjacent to the footpoint of the coronal loop structure.

Title: Computer Vision for the Solar Dynamics Observatory (SDO)
Authors: Martens, P. C. H.; Attrill, G. D. R.; Davey, A. R.; Engell,
   A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar, S. H.;
   Savcheva, A.; Su, Y.; Testa, P.; Wills-Davey, M.; Bernasconi, P. N.;
   Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F.; Cirtain, J. W.;
   DeForest, C. E.; Angryk, R. A.; De Moortel, I.; Wiegelmann, T.;
   Georgoulis, M. K.; McAteer, R. T. J.; Timmons, R. P.
Bibcode: 2012SoPh..275...79M
Altcode: 2011SoPh..tmp..144M; 2011SoPh..tmp..213M; 2011SoPh..tmp....8M
  In Fall 2008 NASA selected a large international consortium to produce
  a comprehensive automated feature-recognition system for the Solar
  Dynamics Observatory (SDO). The SDO data that we consider are all of the
  Atmospheric Imaging Assembly (AIA) images plus surface magnetic-field
  images from the Helioseismic and Magnetic Imager (HMI). We produce
  robust, very efficient, professionally coded software modules that
  can keep up with the SDO data stream and detect, trace, and analyze
  numerous phenomena, including flares, sigmoids, filaments, coronal
  dimmings, polarity inversion lines, sunspots, X-ray bright points,
  active regions, coronal holes, EIT waves, coronal mass ejections
  (CMEs), coronal oscillations, and jets. We also track the emergence and
  evolution of magnetic elements down to the smallest detectable features
  and will provide at least four full-disk, nonlinear, force-free magnetic
  field extrapolations per day. The detection of CMEs and filaments is
  accomplished with Solar and Heliospheric Observatory (SOHO)/Large
  Angle and Spectrometric Coronagraph (LASCO) and ground-based Hα
  data, respectively. A completely new software element is a trainable
  feature-detection module based on a generalized image-classification
  algorithm. Such a trainable module can be used to find features that
  have not yet been discovered (as, for example, sigmoids were in the
  pre-Yohkoh era). Our codes will produce entries in the Heliophysics
  Events Knowledgebase (HEK) as well as produce complete catalogs for
  results that are too numerous for inclusion in the HEK, such as the
  X-ray bright-point metadata. This will permit users to locate data on
  individual events as well as carry out statistical studies on large
  numbers of events, using the interface provided by the Virtual Solar
  Observatory. The operations concept for our computer vision system is
  that the data will be analyzed in near real time as soon as they arrive
  at the SDO Joint Science Operations Center and have undergone basic
  processing. This will allow the system to produce timely space-weather
  alerts and to guide the selection and production of quicklook images and
  movies, in addition to its prime mission of enabling solar science. We
  briefly describe the complex and unique data-processing pipeline,
  consisting of the hardware and control software required to handle
  the SDO data stream and accommodate the computer-vision modules, which
  has been set up at the Lockheed-Martin Space Astrophysics Laboratory
  (LMSAL), with an identical copy at the Smithsonian Astrophysical
  Observatory (SAO).

Title: On the Anti-correlation between Spectral Line Broadening and
    Intensity in Coronal Structures Observed with EIS
Authors: Scott, J. T.; Martens, P. C. H.
Bibcode: 2011ApJ...742..101S
Altcode:
  The advance in spectral resolution of the Extreme Ultraviolet Imaging
  (EIS) spectrometer on board Hinode has allowed for more detailed
  analysis of coronal spectral lines. Large line broadening and
  blueshifted velocities have been found in the periphery of active
  region (AR) cores and near the footpoints of coronal loops. This
  line broadening is yet to be understood. We study the correlation of
  intensity and line width for entire ARs and sub-regions selected to
  include coronal features. The results show that although a slight
  positive correlation can be found when considering whole images,
  many sub-regions have a negative correlation between intensity and
  line width. Sections of a coronal loop display some of the largest
  anti-correlations found for this study with the increased line
  broadening occurring directly adjacent to the footpoint section of
  the loop structure, not at the footpoint itself. The broadened lines
  may be due to a second Doppler-shifted component that is separate from
  the main emitting feature such as a coronal loop, but related in their
  excitation. The small size of these features forces the considerations
  of investigator and instrumental effects. Preliminary analyses are
  shown that indicate the possibility of a point-spread function that
  is not azimuthally symmetric and may affect velocity and line profile
  measurements.

Title: Solar Physics Automated Feature Detection: Progress and
    Scientific Return
Authors: Martens, P. C.; SDO Feature Finding Team
Bibcode: 2011AGUFMSH13B1963M
Altcode:
  The SDO Feature Finding Team (FFT) has been implementing 16 feature
  finding modules for the last two and a half years. These modules
  have been designed to analyze the incoming stream of SDO data in
  near-real-time. Several modules are in regular operation now, most
  others are reaching that point. Our modules detect flares, filaments,
  dimming regions, sigmoids, emerging flux, bright points, jets,
  oscillations, active regions, coronal holes, and several other solar
  features. We are also developing a general trainable feature detection
  module, which can be applied to detect any phenomenon. Automated
  feature recognition has several advantages over the same by humans:
  first, and most importantly, much larger amounts of images can be
  analyzed by machines; second, the codes will apply consistent criteria
  for the detection of phenomena, much more so than humans. Of course
  the second point implies that the detection criteria must be carefully
  calibrated, otherwise the outcome will be consistent, but consistently
  wrong. Examples of the scientific potential unleashed our project are:
  i) Draw a butterfly diagram for Active Regions, ii) Find all filaments
  that coincide with sigmoids, and then correlate sigmoid handedness
  with filament chirality, iii) Correlate EUV jets with small scale flux
  emergence in coronal holes, iv) Draw polarity inversion line maps with
  regions of high shear and large magnetic field gradients overlayed, to
  pinpoint potential flaring regions. Then correlate with actual flare
  occurrence. All of these tasks will be accomplished with great ease;
  the power of this method is limited merely by the imagination of the
  researcher. In addition our modules provide space-weather alerts for
  flares, dimmings (proxies for eruptions), and flux emergence. In my
  presentation I will present an overview of the output from our feature
  detection codes, as well as first results of scientific analysis from
  the metadata.

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.
Bibcode: 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: Simulating the Effects of Initial Pitch-angle Distributions
    on Solar Flares
Authors: Winter, Henry D.; Martens, Petrus; Reeves, Katharine K.
Bibcode: 2011ApJ...735..103W
Altcode:
  In this work, we model both the thermal and non-thermal components of
  solar flares. The model we use, HYLOOP, combines a hydrodynamic equation
  solver with a non-thermal particle tracking code to simulate the thermal
  and non-thermal dynamics and emission of solar flares. In order to test
  the effects of pitch-angle distribution on flare dynamics and emission,
  a series of flares is simulated with non-thermal electron beams injected
  at the loop apex. The pitch-angle distribution of each beam is described
  by a single parameter and allowed to vary from flare to flare. We
  use the results of these simulations to generate synthetic hard and
  soft X-ray emissions (HXR and SXR). The light curves of the flares in
  Hinode's X-ray Telescope passbands show a distinct signal that is highly
  dependent on pitch-angle distribution. The simulated HXR emission in the
  3-6 keV bandpass shows the formation and evolution of emission sources
  that correspond well to the observations of pre-impulsive flares. This
  ability to test theoretical models of thermal and non-thermal flare
  dynamics directly with observations allows for the investigation
  of a wide range of physical processes governing the evolution of
  solar flares. We find that the initial pitch-angle distribution of
  non-thermal particle populations has a profound effect on loop top
  HXR and SXR emission and that apparent motion of HXR is a natural
  consequence of non-thermal particle evolution in a magnetic trap.

Title: Computer Vision for the Solar Dynamics Observatory: First
    Results and What's Next
Authors: Martens, P. C. H.; Sdo Feature Finding Team
Bibcode: 2011ASPC..442..543M
Altcode: 2011adass..20..543M
  The Solar Dynamics Observatory (SDO) feature finding team is a large
  international consortium tasked by NASA to produce a comprehensive
  system for automated feature recognition for SDO. We are producing
  robust and very efficient software modules that can keep up with the SDO
  data stream and detect, trace, and analyze a large number of phenomena,
  including flares, sigmoids, filaments, and coronal dimmings. Results
  will be shown for several modules have been inaugurated since the end
  of SDO commissioning last summer. In addition a description is given
  of the status of the development of our trainable automated feature
  finding module.

Title: Recent Improvements of Kinematic Models of the Solar Magnetic
    Cycle
Authors: Muñoz-Jaramillo, Andrés; Nandy, Dibyendu; Martens, Petrus
   C. H.
Bibcode: 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.
Bibcode: 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.
Bibcode: 2011SPD....42.1705M
Altcode: 2011BAAS..43S.1705M
  Nandy, Munoz, &amp; 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 &amp;
  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 &amp; 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 &amp; Rightmire,
  Basu &amp; Antia, and the model assumptions of Nandy, Munoz, &amp;
  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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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: Heliophysics Data Environment: What's next? (Invited)
Authors: Martens, P.
Bibcode: 2010AGUFMSM34A..06M
Altcode:
  In the last two decades the Heliophysics community has witnessed
  the societal recognition of the importance of space weather and
  space climate for our technology and ecology, resulting in a renewed
  priority for and investment in Heliophysics. As a result of that and
  the explosive development of information technology, Heliophysics has
  experienced an exponential growth in the amount and variety of data
  acquired, as well as the easy electronic storage and distribution of
  these data. The Heliophysics community has responded well to these
  challenges. The first, most obvious and most needed response, was the
  development of Virtual Heliophysics Observatories. While the VxOs of
  Heliophysics still need a lot of work with respect to the expansion of
  search options and interoperability, I believe the basic structures and
  functionalities have been established, and that they meet the needs
  of the community. In the future we'll see a refinement, completion,
  and integration of VxOs, not a fundamentally different approach --
  in my opinion. The challenge posed by the huge increase in amount
  of data is not met by VxOs alone. No individual scientist or group,
  even with the assistance of tons of graduate students, can analyze the
  torrent of data currently coming down from the fleet of heliospheric
  observatories. Once more information technology provides an opportunity:
  Automated feature recognition of solar imagery is feasible, has been
  implemented in a number of instances, and is strongly supported by
  NASA. For example, the SDO Feature Finding Team is developing a suite
  of 16 feature recognition modules for SDO imagery that operates in
  near-real time, produces space-weather warnings, and populates on-line
  event catalogs. Automated feature recognition -- "computer vision"
  -- not only save enormous amounts of time in the analysis of events,
  it also allows for a shift from the analysis of single events to
  that of sets of features and events -- the latter being by far the
  most important implication of computer vision. Consider some specific
  examples of possibilities here: From the on-line SDO metadata a user
  can produce with a few IDL line commands information that previously
  would have taken years to compile, e.g.: - Draw a butterfly diagram for
  Active Regions, - Find all filaments that coincide with sigmoids and
  correlate the automatically detected sigmoid handedness with filament
  chirality, - Correlate EUV jets with small scale flux emergence in
  coronal holes only, - Draw PIL maps with regions of high shear and
  large magnetic field gradients overlayed, to pinpoint potential
  flaring regions. Then correlate with actual flare occurrence. I
  emphasize that the access to those metadata will be provided by VxOs,
  and that the interplay between computer vision codes and data will be
  facilitated by VxOs. My vision for the near and medium future for the
  VxOs is then to provide a simple and seamless interface between data,
  cataloged metadata, and computer vision software, either existing or
  newly developed by the user. Heliospheric virtual observatories and
  computer vision systems will work together to constantly monitor the
  Sun, provide space weather warnings, populate catalogs of metadata,
  analyze trends, and produce real-time on-line imagery of current events.

Title: Accessing SDO data in a pipeline environment using the VSO
    WSDL/SOAP interface
Authors: Suarez Sola, F. I.; Hourcle, J. A.; Amezcua, A.; Bogart,
   R.; Davey, A. R.; Gurman, J. B.; Hill, F.; Hughitt, V. K.; Martens,
   P. C.; Spencer, J.; Vso Team
Bibcode: 2010AGUFMSH23C1869S
Altcode:
  As part of the Virtual Solar Observatory (VSO) effort to support the
  Solar Dynamics Observatory (SDO) data, the VSO has worked on bringing
  up to date its WSDL document and SOAP interface to make it compatible
  with most widely used web services core engines. (E.g. axis2, jws,
  etc.) In this presentation we will explore the possibilities available
  for searching and/or fetching data within pipeline code. We will explain
  some of the WSDL/VSO-SDO interface intricacies and show how the vast
  amount of data that is available via the VSO can be tapped via IDL,
  Java, Perl or C in an uncomplicated way.

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.
Bibcode: 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: Empirical Modeling of Radiative versus Magnetic Flux for
    the Sun-as-a-Star
Authors: Preminger, Dora; Nandy, Dibyendu; Chapman, Gary; Martens,
   Petrus C. H.
Bibcode: 2010SoPh..264...13P
Altcode: 2010arXiv1006.4354P; 2010SoPh..tmp...92P
  We study the relationship between full-disk solar radiative flux at
  different wavelengths and average solar photospheric magnetic-flux
  density, using daily measurements from the Kitt Peak magnetograph
  and other instruments extending over one or more solar cycles. We
  use two different statistical methods to determine the underlying
  nature of these flux - flux relationships. First, we use statistical
  correlation and regression analysis and show that the relationships are
  not monotonic for total solar irradiance and for continuum radiation
  from the photosphere, but are approximately linear for chromospheric
  and coronal radiation. Second, we use signal theory to examine the
  flux - flux relationships for a temporal component. We find that
  a well-defined temporal component exists and accounts for some of
  the variance in the data. This temporal component arises because
  active regions with high magnetic-field strength evolve, breaking
  up into small-scale magnetic elements with low field strength, and
  radiative and magnetic fluxes are sensitive to different active-region
  components. We generate empirical models that relate radiative flux to
  magnetic flux, allowing us to predict spectral-irradiance variations
  from observations of disk-averaged magnetic-flux density. In most cases,
  the model reconstructions can account for 85 - 90% of the variability
  of the radiative flux from the chromosphere and corona. Our results
  are important for understanding the relationship between magnetic and
  radiative measures of solar and stellar variability.

Title: Solar Cycle Variation of Magnetic Flux Ropes in a Quasi-Static
    Coronal Evolution Model
Authors: Yeates, A. R.; Constable, J. A.; Martens, P. C. H.
Bibcode: 2010SoPh..263..121Y
Altcode: 2010arXiv1003.4653Y; 2010SoPh..tmp...69Y
  The structure of electric current and magnetic helicity in the solar
  corona is closely linked to solar activity over the 11-year cycle,
  yet is poorly understood. As an alternative to traditional current-free
  "potential-field" extrapolations, we investigate a model for the global
  coronal magnetic field which is non-potential and time-dependent,
  following the build-up and transport of magnetic helicity due to
  flux emergence and large-scale photospheric motions. This helicity
  concentrates into twisted magnetic flux ropes, which may lose
  equilibrium and be ejected. Here, we consider how the magnetic
  structure predicted by this model - in particular the flux ropes -
  varies over the solar activity cycle, based on photospheric input
  data from six periods of cycle 23. The number of flux ropes doubles
  from minimum to maximum, following the total length of photospheric
  polarity inversion lines. However, the number of flux rope ejections
  increases by a factor of eight, following the emergence rate of active
  regions. This is broadly consistent with the observed cycle modulation
  of coronal mass ejections, although the actual rate of ejections in the
  simulation is about a fifth of the rate of observed events. The model
  predicts that, even at minimum, differential rotation will produce
  sheared, non-potential, magnetic structure at all latitudes.

Title: Towards better Constrained Kinematic Dynamo Models: Turbulent
    Diffusivity and Diffusivity Quenching
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
Bibcode: 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: Scaling Laws and Temperature Profiles for Solar and Stellar
    Coronal Loops with Non-uniform Heating
Authors: Martens, P. C. H.
Bibcode: 2010ApJ...714.1290M
Altcode: 2008arXiv0804.2241M
  The bulk of solar coronal radiative loss consists of soft X-ray
  emission from quasi-static loops at the cores of active regions. In
  order to develop diagnostics for determining the heating mechanism of
  these loops from observations by coronal imaging instruments, I have
  developed analytical solutions for the temperature structure and scaling
  laws of loop strands for a set of temperature- and pressure-dependent
  heating functions that encompass heating concentrated at the footpoints,
  uniform heating, and heating concentrated at the loop apex. Key results
  are that the temperature profile depends only weakly on the heating
  distribution—not sufficiently to be of significant diagnostic
  value—and that the scaling laws survive for this wide range of
  heating distributions, but with the constant of proportionality in the
  Rosner-Tucker-Vaiana scaling law (P <SUB>0</SUB> L ~ T <SUP>3</SUP>
  <SUB>max</SUB>) depending on the specific heating function. Furthermore,
  quasi-static solutions do not exist for an excessive concentration of
  heating near the loop footpoints, a result in agreement with recent
  numerical simulations. It is demonstrated that a generalization of
  the results to a set of solutions for strands with a functionally
  prescribed variable diameter leads to only relatively small correction
  factors in the scaling laws and temperature profiles for constant
  diameter loop strands. A quintet of leading theoretical coronal
  heating mechanisms is shown to be captured by the formalism of this
  paper, and the differences in thermal structure between them may be
  verified through observations. Preliminary results from full numerical
  simulations demonstrate that, despite the simplifying assumptions,
  the analytical solutions from this paper are accurate and stable.

Title: Computer Vision for SDO: First Results from the SDO Feature
    Finding Algorithms
Authors: Martens, Petrus C.; Attrill, G.; Davey, A.; Engell, A.;
   Farid, S.; Grigis, P.; Kasper, J.; Korreck, K.; Saar, S.; Su, Y.;
   Testa, P.; Wills-Davey, M.; Bernasconi, P.; Raouafi, N.; Georgoulis,
   M.; Deforest, C.; Peterson, J.; Berghoff, T.; Delouille, V.; Hochedez,
   J.; Mampaey, B.; Verbeek, C.; Cirtain, J.; Green, S.; Timmons, R.;
   Savcheva, A.; Angryk, R.; Wiegelmann, T.; McAteer, R.
Bibcode: 2010AAS...21630804M
Altcode:
  The SDO Feature Finding Team produces robust and very efficient
  software modules that can keep up with the relentless SDO data stream,
  and detect, trace, and analyze a large number of phenomena including:
  flares, sigmoids, filaments, coronal dimmings, polarity inversion
  lines, sunspots, X-ray bright points, active regions, coronal holes,
  EIT waves, CME's, coronal oscillations, and jets. In addition we track
  the emergence and evolution of magnetic elements down to the smallest
  features that are detectable, and we will also provide at least four
  full disk nonlinear force-free magnetic field extrapolations per day. <P
  />During SDO commissioning we will install in the near-real time data
  pipeline the modules that provide alerts for flares, coronal dimmings,
  and emerging flux, as well as those that trace filaments, sigmoids,
  polarity inversion lines, and active regions. We will demonstrate
  the performance of these modules and illustrate their use for science
  investigations.

Title: Are Active Regions as Relevant for the Solar Cycle as we Think?
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
Bibcode: 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.
Bibcode: 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: The SDO flare detective
Authors: Grigis, Paolo; Davey, A.; Martens, P.; Testa, P.; Timmons,
   R.; Su, Y.; SDO Feature Finding Team
Bibcode: 2010AAS...21640208G
Altcode: 2010BAAS...41..874G
  We present the flare detective, a software module to automatically
  detect and characterize solar flares observed with the Atmospheric
  Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The
  flare detective works in two steps. First, flares are detected in
  EUV images by analyzing lightcurves in macropixels. At this time,
  only basic quantities such as time intervals, positions, and peak
  fluxes will be determined. This will allow the module to keep up
  with the extremely large size of the incoming data stream and provide
  near real-time information for space weather monitoring. Second, the
  flare detective will be run again on the subset of images around the
  time intervals where a flare has been already detected, where more
  sophisticated (and slower) processing will be performed to better
  characterize the flare and provide physically important parameters such
  as temperatures and emission measures, projected areas and lightcurves
  in different channels. The events detected will be made available to
  the Heliophysics Events Knowledgebase (HEK) and also as a flare list
  in text format accessible on the web. This module is part of a larger
  effort to detect and track solar features and events that is optimized
  to run on the very large datasets provided by SDO.

Title: SDO Data Access Via The Virtual Solar Observatory
Authors: Hill, Frank; Gurman, J.; Martens, P.; Bogart, R.; Davey, A.;
   Hourcle, J.; Suarez Sola, F.; Hughitt, K.; Spencer, J.; Reardon, K.;
   Amezcua, A.
Bibcode: 2010AAS...21640218H
Altcode: 2010BAAS...41Q.876H
  The launch of SDO brings not only the prospect of new solar physics
  discoveries, but also a flood of data. The sustained data rate of
  150 Mbs (about 1.6 TB per day) is the highest yet produced by a
  solar physics observatory, and the handling of the data requires new
  methods. One approach is to distribute the data storage and request
  system over a number of distinct sites to reduce the bandwidth
  requirements at a single location. The VSO, in conjunction with the
  Joint Science and Operations Center (JSOC) at Stanford and a network of
  partial archive sites currently at CfA, NSO, ROB, and MPIS, is now able
  to provide metadata search and data retrieval services for the SDO AIA
  and HMI instruments. EVE data will also be included in the future. This
  talk will describe how SDO data can be accessed via the VSO.

Title: Comparison of a Global Magnetic Evolution Model with
    Observations of Coronal Mass Ejections
Authors: Yeates, A. R.; Attrill, G. D. R.; Nandy, Dibyendu; Mackay,
   D. H.; Martens, P. C. H.; van Ballegooijen, A. A.
Bibcode: 2010ApJ...709.1238Y
Altcode: 2009arXiv0912.3347Y
  The relative importance of different initiation mechanisms for coronal
  mass ejections (CMEs) on the Sun is uncertain. One possible mechanism is
  the loss of equilibrium of coronal magnetic flux ropes formed gradually
  by large-scale surface motions. In this paper, the locations of flux
  rope ejections in a recently developed quasi-static global evolution
  model are compared with observed CME source locations over a 4.5 month
  period in 1999. Using extreme ultraviolet data, the low-coronal source
  locations are determined unambiguously for 98 out of 330 CMEs. An
  alternative method of determining the source locations using recorded
  Hα events was found to be too inaccurate. Despite the incomplete
  observations, positive correlation (with coefficient up to 0.49) is
  found between the distributions of observed and simulated ejections,
  but only when binned into periods of 1 month or longer. This binning
  timescale corresponds to the time interval at which magnetogram data are
  assimilated into the coronal simulations, and the correlation arises
  primarily from the large-scale surface magnetic field distribution;
  only a weak dependence is found on the magnetic helicity imparted to the
  emerging active regions. The simulations are limited in two main ways:
  they produce fewer ejections, and they do not reproduce the strong
  clustering of observed CME sources into active regions. Due to this
  clustering, the horizontal gradient of radial photospheric magnetic
  field is better correlated with the observed CME source distribution
  (coefficient 0.67). Our results suggest that while the gradual formation
  of magnetic flux ropes over weeks can account for many observed CMEs,
  especially at higher latitudes, there exists a second class of CMEs (at
  least half) for which dynamic active region flux emergence on shorter
  timescales must be the dominant factor. Improving our understanding
  of CME initiation in future will require both more comprehensive
  observations of CME source regions and more detailed magnetic field
  simulations.

Title: Automated Feature and Event Detection with SDO AIA and HMI Data
Authors: Davey, Alisdair; Martens, P. C. H.; Attrill, G. D. R.;
   Engell, A.; Farid, S.; Grigis, P. C.; Kasper, J.; Korreck, K.; Saar,
   S. H.; Su, Y.; Testa, P.; Wills-Davey, M.; Savcheva, A.; Bernasconi,
   P. N.; Raouafi, N. -E.; Delouille, V. A.; Hochedez, J. F. .; Cirtain,
   J. W.; Deforest, C. E.; Angryk, R. A.; de Moortel, I.; Wiegelmann,
   T.; Georgouli, M. K.; McAteer, R. T. J.; Hurlburt, N.; Timmons, R.
Bibcode: 2010cosp...38.2878D
Altcode: 2010cosp.meet.2878D
  The Solar Dynamics Observatory (SDO) represents a new frontier in
  quantity and quality of solar data. At about 1.5 TB/day, the data will
  not be easily digestible by solar physicists using the same methods
  that have been employed for images from previous missions. In order for
  solar scientists to use the SDO data effectively they need meta-data
  that will allow them to identify and retrieve data sets that address
  their particular science questions. We are building a comprehensive
  computer vision pipeline for SDO, abstracting complete metadata
  on many of the features and events detectable on the Sun without
  human intervention. Our project unites more than a dozen individual,
  existing codes into a systematic tool that can be used by the entire
  solar community. The feature finding codes will run as part of the SDO
  Event Detection System (EDS) at the Joint Science Operations Center
  (JSOC; joint between Stanford and LMSAL). The metadata produced will
  be stored in the Heliophysics Event Knowledgebase (HEK), which will be
  accessible on-line for the rest of the world directly or via the Virtual
  Solar Observatory (VSO) . Solar scientists will be able to use the
  HEK to select event and feature data to download for science studies.

Title: Enabling Distributed Search and Access to SDO Data with the
    Virtual Solar Observatory
Authors: Davey, Alisdair; Martens, P.; Gurman, J.; Hourcle, J.; Hill,
   F.; Suarez-Sola, F.; Amezcua, A.; Bogart, R.; Spencer, J.
Bibcode: 2010cosp...38.2881D
Altcode: 2010cosp.meet.2881D
  The Virtual Solar Observatory (VSO) will be an integral part of
  distributing Solar Dynamics Observatory (SDO) data to the Solar Physics
  community and in enabling it to be searched by scientists. A daily
  data volume of 1.5TB presents unique challenges, and the VSO has been
  working on enhancing various aspects of its infrastructure to deal with
  them. The VSO will provide a dedicated interface to SDO data, providing
  common methods users of VSO already know, as well as new methods that
  reflect the needs of interacting with AIA, HMI and EVE data. VSO has
  created a data distribution architecture based up the Joint Science
  Operations Center (JSOC) infrastructure, that in partnership with
  NASA Solar Data Analysis Center, National Solar Observatory, Royal
  Observatory Belgium, University College Lancashire, Max Planck Institute
  for Solar System Research and the Institute d'Astrophysique Spatiale
  (Orsay) will enable scientists to retrieve SDO data of interest in
  the fastest possible way. VSO is working closely with the Helioviewer
  and Heliophysics Event Knowledgebase (HEK) teams to ensure we will
  be able to use their efforts and be used by their efforts for data
  retrieval. In this manner, graphical, IDL-based and event approaches
  to data discovery will be fully supported by the VSO.

Title: The SDO Flare Detective
Authors: Grigis, P. C.; Davey, A. R.; Martens, P. C.; Su, Y.; Testa,
   P.; Timmons, R. P.
Bibcode: 2009AGUFMSH51B1277G
Altcode:
  We present the flare detective, a software module to automatically
  detect and characterize solar flares observed with the Atmospheric
  Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The
  flare detective works in two steps. First, flares will be detected
  in EUV images by analysing lightcurves in macropixels. At this time,
  only basic quantities such as time intervals, positions, and peak
  fluxes will be determined. This will allow the module to keep up
  with the extremely large size of the incoming data stream and provide
  near real-time information for space weather monitoring. Second, the
  flare detective will be run again on the subset of images around the
  time intervals where a flare has been already detected, where more
  sophisticated (and slower) processing will be performed to better
  characterize the flare and provide physically important parameters such
  as temperatures and emission measures, projected areas and lightcurves
  in different channels. The events detected will be made available to
  the Heliophysics Knowledgebase (HEK) and also as a flare list in text
  format accessible on the web. This module is part of a larger effort
  to detect and track solar features and events that is optimized to
  run on very large datasets such as the ones provided by SDO.

Title: Computer Vision for the Solar Dynamics Observatory
Authors: Martens, P. C.
Bibcode: 2009AGUFMSH51B1276M
Altcode:
  NASA has selected our large international consortium last year to
  produce a comprehensive system for automated feature recognition in
  SDO images. The data we consider are all AIA and EVE data plus surface
  magnetic field images from HMI. Helioseismology is addressed by another
  group. We are producing robust and very efficient software modules
  that can keep up with the relentless SDO data stream and detect, trace,
  and analyze a large number of phenomena, including: flares, sigmoids,
  filaments, coronal dimmings, polarity inversion lines, sunspots,
  X-ray bright points, active regions, coronal holes, EIT waves, CME's,
  coronal oscillations, and jets. In addition we will track the emergence
  and evolution of magnetic elements down to the resolution limit, and we
  will also provide at least four full disk nonlinear force-free magnetic
  field extrapolations per day. A completely new software element that
  rounds out this suite is a trainable feature detection module, which
  employs a generalized image classification algorithm to produce the
  texture features of the images analyzed. A user can introduce a number
  of examples of the phenomenon looked for and the software will return
  images with similar features. We have tested a proto-type on TRACE
  data, and were able to "train" the algorithm to detect sunspots, active
  regions, and loops. Such a module can be applied to find features that
  have not even been discovered yet, as, for example, sigmoids were in
  the pre-Yohkoh era. In addition it will be used to detect features for
  which we will not develop dedicated modules, such as loops, arcades,
  "null"-type geometries, anemones, delta-spots, etc. Our codes will
  produce entries in the Heliophysics Events Knowledge base, and that
  will permit users to locate data on individual events as well as carry
  out statistical studies on large numbers of events.

Title: What do Solar Kinematic Models Tell us About the Current
    Minimum?
Authors: Muñoz-Jaramillo, A.; Nandy, D.; Martens, P. C.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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: Computer Vision for The Solar Dynamics Observatory
Authors: Martens, Petrus C.; Angryk, R. A.; Bernasconi, P. N.; Cirtain,
   J. W.; Davey, A. R.; DeForest, C. E.; Delouille, V. A.; De Moortel,
   I.; Georgoulis, M. K.; Grigis, P. C.; Hochedez, J. E.; Kasper, J.;
   Korreck, K. E.; Reeves, K. K.; Saar, S. H.; Savcheva, A.; Su, Y.;
   Testa, P.; Wiegelmann, T.; Wills-Davey, M.
Bibcode: 2009SPD....40.1711M
Altcode:
  NASA funded a large international consortium last year to produce
  a comprehensive system for automated feature recognition in SDO
  images. The data we consider are all AIA and EVE data plus surface
  magnetic field images from HMI. Helioseismology is addressed by another
  group. <P />We will produce robust and very efficient software modules
  that can keep up with the relentless SDO data stream and detect, trace,
  and analyze a large number of phenomena, including: flares, sigmoids,
  filaments, coronal dimmings, polarity inversion lines, sunspots,
  X-ray bright points, active regions, coronal holes, EIT waves, CME's,
  coronal oscillations, and jets. In addition we will track the emergence
  and evolution of magnetic elements down to the smallest features
  that are detectable, and we will also provide at least four full
  disk nonlinear force-free magnetic field extrapolations per day. <P
  />A completely new software element that rounds out this suite is a
  trainable feature detection module, which employs a generalized image
  classification algorithm to produce the texture features of the images
  analyzed. A user can introduce a number of examples of the phenomenon
  looked and the software will return images with similar features. We
  have tested a proto-type on TRACE data, and were able to "train" the
  algorithm to detect sunspots, active regions, and loops. Such a module
  can be used to find features that have not even been discovered yet,
  as, for example, sigmoids were in the pre-Yohkoh era. <P />Our codes
  will produce entries in the Helio Events Knowledge base, and that will
  permit users to locate data on individual events as well as carry out
  statistical studies on large numbers of events, using the interface
  provided by the Virtual Solar Observatory.

Title: The Virtual Solar Observatory: Where Do We Go from Here?
Authors: Gurman, Joseph B.; Bogart, R.; Spencer, J.; Hill, F.; Suarez
   Sola, I.; Reardon, K.; Hourcle, J.; Hughitt, K.; Martens, P.; Davey, A.
Bibcode: 2009SPD....40.1508G
Altcode:
  The Virtual Solar Observatory (VSO) continues to add features in an
  effort to broaden the ways in which it can be used to aid research. We
  describe and demonstrate plans for SDO data access (see also the poster
  Suarez-Sola et al.), multiple catalog access (Hourclé et al.), and
  new capabilities of the IDL VSO_SEARCH function, as well as describing
  future capabilities in development and under consideration. <P />Since
  the VSO is funded by the Solar Data Analysis Center (SDAC), which will
  be undergoing a NASA Senior Review in July, we solicit community input
  to help us prioritize this new work: what should we do with the limited
  resources available?

Title: The Off-Axis Properties of the Hinode X-Ray Telescope (XRT):
    I. Vignetting Effect
Authors: Shin, Junho; Martens, P. C. H.; Golub, L.; Deluca, E. E.
Bibcode: 2009SPD....40.1804S
Altcode:
  The X-Ray Telescope (XRT) aboard Hinode has observed a variety
  of coronal structures in the range of 34x34 arc min field-of-view
  (FOV) covering the full solar disk. In general, most astronomical
  telescopes are designed such that the best-focused image of an object
  can be achieved at or close to the on-axis position, and the optical
  performance varies systematically across the FOV. The Sun is, however,
  a large object whose size is about 30 arc min and coronal structures
  are observed not only at the disc center but also near the limb. For
  this reason, the optical structure of solar telescopes should be
  designed with care for improving the uniformity of the angular
  resolution over the full FOV. Since there is no unique solution for
  successfully implementing this kind of off-axis variation, the optical
  properties of the XRT have been examined using the data from the ground
  experiments as well as from in-flight observations for the calibration
  of systematic variations in the FOV. <P />The vignetting effect is an
  important optical characteristic for describing the performance of
  the telescope, which reflects the ability to collect incoming light
  at different locations and different photon energies. Especially,
  the determination of this vignetting effect is one of the essential
  calibration steps that should be performed before the observed images
  are used for any scientific purposes. Because a component of the
  XRT vignetting effect shows a wavelength dependence, special care
  should be taken when, for example, performing temperature analyses
  with thin and thick filters of flares occurring near the solar
  limb. In this presentation, we introduce the results of analysis of
  pre-launch calibration data obtained from MSFC/XRCF experiments. The
  two-dimensional off-axis variation of the XRT point spread function
  (PSF) and its energy dependence will be discussed in detail.

Title: The Unusual Minimum of Cycle 23: Observations and
    Interpretation
Authors: Martens, Petrus C.; Nandy, D.; Munoz-Jaramillo, A.
Bibcode: 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: Properties of a Coronal Loop Structure with EIS, TRACE,
    and STEREO
Authors: Scott, Jason; Martens, P. C. H.; McKenzie, D.
Bibcode: 2009SPD....40.1217S
Altcode:
  The physical properties of a coronal loop structure are investigated
  using three EUV observing instruments. The density, thermal width,
  and lifetime of a loop structure are found. Spectral coverage from
  EIS provides density and thermal information. Observations from TRACE
  and STEREO show the structure's geometry and intensity as a function
  of time in multiple wavebands. The isolated loop is straightened
  and characterized by a Gaussian fit to perpendicular cross-cuts of
  the observed structure. This allows for the extraction of background
  subtracted intensities which is important when isolating the coronal
  structure for analysis. These background subtracted intensities are
  then used to determine the thermal characteristics (temperature,
  emission measure ), density, structure width, and lifetime. These
  results provide much needed measurements of coronal loop structure.

Title: Towards Better Constrained Solar Dynamo Models: The Velocity
    Field And Turbulent Diffusivity Profiles
Authors: Munoz-Jaramillo, Andres; Nandy, D.; Martens, P. C. H.
Bibcode: 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: Radiative Vs. Magnetic Flux For The Sun-as-a-star
Authors: Preminger, D.; Nandi, D.; Chapman, G.; Martens, P.
Bibcode: 2009SPD....40.1111P
Altcode:
  We study the relationship between full-disk solar radiative flux at
  different wavelengths and average solar photospheric magnetic flux
  density, using daily measurements from the Kitt Peak magnetograph
  and other instruments extending over one or more solar cycles. We
  use statistical methods to determine the underlying nature of these
  flux-flux relationships. For total solar irradiance and for continuum
  radiation from the photosphere, the relationships are non-linear, but
  for chromospheric and coronal radiation the relationships are linear. We
  find that scatter plots of radiative flux vs Kitt Peak magnetic flux
  density show significant variance, due in part to the presence of a
  temporal component in some of the flux-flux relationships. This temporal
  relationship arises because an active region with high magnetic field
  strength evolves, breaking up into small-scale components with low
  field strength, while the Kitt Peak magnetic field measurements are
  somewhat insensitive to very strong and very weak magnetic fields. We
  find that average magnetic flux density measured by Kitt Peak can be
  used as a proxy for radiative flux, but with limited accuracy.

Title: Modeling Thermal and Nonthermal Flare Dynamics with HyLoop
Authors: Winter, Henry (Trae) D., III; Martens, P.
Bibcode: 2009SPD....40.3607W
Altcode:
  It is generally agreed that the energy for solar flares comes from
  stressed magnetic fields. However, the mechanisms that convert that
  energy into the heating of the thermal plasma and the acceleration
  of nonthermal particles remain a topic of debate. In order to test
  models governing flare heating and particle acceleration, state of
  the art numerical codes that can simulate both the interaction of
  thermal and nonthermal particles in a self-consistent manner and
  the electromagnetic emission are required. To this end, the HyLoop
  simulation suite was developed. HyLoop combines a hydrodynamic equation
  solver with a nonthermal particle tracking code to simulate the thermal
  and nonthermal dynamics and emission of solar flares. A sophisticated
  imaging package allows for the direct comparison of simulated results
  to current and future solar observatories including XRT and RHESSI. In
  order to test the effects of pitch-angle distribution on flare dynamics
  and emission, a series of flares were simulated with nonthermal
  electron beams injected at the loop apex. The pitch-angle distribution
  of each beam was described by a single parameter and allowed to vary
  from flare to flare. The lightcurves of the flares in XRT bandpasses
  showed a distinct signal that was a highly dependent on pitch-angle
  distribution. The simulated HXR emission in the 3-6 keV bandpass showed
  the formation and evolution of emission sources that corresponded well
  to the observations of pre-impulsive flares. The initial conditions
  of the simulations necessitated a significantly different physical
  interpretation of this motion than previous work. This ability to test
  theoretical models of thermal and nonthermal flare dynamics directly
  with observations allows for the investigation of a wide range of
  physical processes governing the release of energy in solar flares.

Title: The Virtual Solar Observatory—A Resource for International
    Heliophysics Research
Authors: Hill, Frank; Martens, Piet; Yoshimura, Keji; Gurman, Joseph;
   Hourclé, Joseph; Dimitoglou, George; Suárez-Solá, Igor; Wampler,
   Steve; Reardon, Kevin; Davey, Alisdair; Bogart, Richard S.; Tian,
   Karen Q.
Bibcode: 2009EM&P..104..315H
Altcode: 2008EM&P..tmp...47H
  The Virtual Solar Observatory (VSO) has been developed to allow
  researchers, educators, and the general public to access data
  and images from the major sources of on-line solar data. The VSO
  substantially reduces the effort required to locate disparate data
  sets, and removes the need for the user to locate the data and
  learn multiple interfaces. The VSO provides a single interface to
  about 60 geographically distributed data sets including space- and
  ground-based sources. These data sets incorporate several physical
  variables including magnetic field, intensity, Doppler velocity, etc.,
  and all wavelengths from X-ray to radio. All layers of the sun, from
  the interior to the corona, are included. In this paper we describe
  the system and present the interface that the user will encounter. We
  also discuss future enhancements planned for the system.

Title: Solar Coronal Structure and Stray Light in TRACE
Authors: DeForest, C. E.; Martens, P. C. H.; Wills-Davey, M. J.
Bibcode: 2009ApJ...690.1264D
Altcode: 2008arXiv0808.3980D
  Using the 2004 Venus transit of the Sun to constrain a semiempirical
  point-spread function (PSF) for the TRACE EUV solar telescope, we
  have measured the effect of stray light in that telescope. We find
  that 43% of 171 Å EUV light that enters TRACE is scattered, either
  through diffraction off the entrance filter grid or through other
  nonspecular effects. We carry this result forward, via known-PSF
  deconvolution of TRACE images, to identify its effect on analysis
  of TRACE data. Known-PSF deconvolution by this derived PSF greatly
  reduces the effect of visible haze in the TRACE 171 Å images, enhances
  bright features, and reveals that the smooth background component of
  the corona is considerably less bright (and hence more rarefied) than
  might otherwise be supposed. Deconvolution reveals that some prior
  conclusions about the Sun appear to have been based on stray light in
  the images. In particular, the diffuse background "quiet corona" becomes
  consistent with hydrostatic support of the coronal plasma; feature
  contrast is greatly increased, possibly affecting derived parameters
  such as the form of the coronal heating function; and essentially all
  existing differential emission measure studies of small features appear
  to be affected by contamination from nearby features. We speculate on
  further implications of stray light for interpretation of EUV images
  from TRACE and similar instruments, and advocate deconvolution as a
  standard tool for image analysis with future instruments.

Title: Analysis of Two Coronal Loops with Combined TRACE and
    SOHO/CDS Data
Authors: Scott, J. T.; Martens, P. C. H.; Cirtain, J. W.
Bibcode: 2008SoPh..252..293S
Altcode: 2008SoPh..tmp..160S
  We use an innovative research technique to analyze combined images from
  the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric
  Observatory (SOHO) and the Transition Region and Coronal Explorer
  (TRACE). We produce a high spatial and temporal resolution simulated
  CDS raster or "composite" map from TRACE data and use this composite
  map to jointly analyze data from both instruments. We show some of
  the advantages of using the "composite" map method for coronal loop
  studies. We investigate two postflare loop structures. We find cool
  material (250 000 K) concentrated at the tips or apex of the loops. This
  material is found to be above its scale height and therefore not in
  hydrostatic equilibrium. The exposure times of the composite map and
  TRACE images are used to give an estimate of another loop's cooling
  time. The contribution to the emission in the TRACE images for the
  spectral lines present in its narrow passband is estimated by using the
  CDS spectral data and CHIANTI to derive synthetic spectra. We obtain
  cospatial and cotemporal data collected by both instruments in SOHO
  Joint Observations Program (JOP) 146 and show how the combination of
  these data can be utilized to obtain more accurate measurements of
  coronal plasmas than if analyzed individually.

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.
Bibcode: 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.

Title: Moving Beyond Time: New VSO Searches
Authors: Davey, A.; Bogart, R.; Gurman, J.; Hill, F.; Hourcle, J.;
   Martens, P.; Suarez Sola, I.; VSO Team
Bibcode: 2008AGUSMSP54A..06D
Altcode:
  Since its inception the Virtual Solar Observatory (VSO) has supported
  a standard set of search parameters for finding data sets of interest,
  including instrument, spectral range and observable, all keyed on
  a defined time range. The VSO also allows users to derive search
  periods based on feature or event catalogs. Recent work on the catalog
  infrastructure will enable far more complex science based queries to
  derive both stand alone results and also starting points for querying
  other data sets. The technical side of this work is presented at
  this meeting in 'Event and Feature Catalogs in the Virtual Solar
  Observatory' by Joe Hourcle et al. This abstract focuses on the
  science made possible by this catalog work and from work to extend
  the standard query mechanisms. In the future we will be able to answer
  queries such as 'show me data sets suitable for DEM analysis' or 'give
  me an image every ten minutes from this instrument.' This effort has
  obvious application to handling SDO data.

Title: Still Virtual After All These Years: Recent Developments in
    the Virtual Solar Observatory
Authors: Gurman, J. B.; Bogart, R. S.; Davey, A. R.; Hill, F.; Martens,
   P. C.; Zarro, D. M.; Team, T. v.
Bibcode: 2008AGUSMSP51B..17G
Altcode:
  While continuing to add access to data from new missions, including
  Hinode and STEREO, the Virtual Solar Observatory is also being enhanced
  as a research tool by the addition of new features such as the unified
  representation of catalogs and event lists (to allow joined searches
  in two or more catalogs) and workable representation and manipulation
  of large numbers of search results (as are expected from the Solar
  Dynamics Observatory database). Working with our RHESSI colleagues,
  we have also been able to improve the performance of IDL-callable
  vso_search and vso_get functions, to the point that use of those
  routines is a practical alternative to reproducing large subsets of
  mission data on one's own LAN.

Title: Twisted solar active region magnetic fields as drivers of
space weather: Observational and theoretical investigations
Authors: Nandy, Dibyendu; Mackay, Duncan H.; Canfield, Richard C.;
   Martens, P. C. H.
Bibcode: 2008JASTP..70..605N
Altcode:
  The properties and dynamics of magnetic fields on the Sun's photosphere
  and outer layers--notably those within solar active regions--govern
  the eruptive activity of the Sun. These photospheric magnetic
  fields also act as the evolving lower boundary of the Sun-Earth
  coupled system. Quantifying the physical attributes of these magnetic
  fields and exploring the mechanisms underlying their influence on the
  near-Earth space environment are of vital importance for forecasting
  and mitigating adverse space weather effects. In this context, we
  discuss here a novel technique for measuring twist in the magnetic
  field lines of solar active regions that does not invoke the force-free
  field assumption. Twist in solar active regions can play an important
  role in flaring activity and the initiation of CMEs via the kink
  instability mechanism; we outline a procedure for determining this
  solar active region eruptive potential. We also discuss how twist in
  active region magnetic fields can be used as inputs in simulations of
  the coronal and heliospheric fields; specifically, we explore through
  simulations, the formation, evolution and ejection of magnetic flux
  ropes that originate in twisted magnetic structures. The results and
  ideas presented here are relevant for exploring the role of twisted
  solar active region magnetic fields and flux ropes as drivers of space
  weather in the Sun-Earth system.

Title: Callable Virtual Observatory Functionality: Sample Use Cases
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
   Hill, F.; Suárez-Solá, I.; Zarro, D. M.; Davey, A. R.; Martens,
   P. C.; Yoshimura, K.
Bibcode: 2007AGUFMSH51A0259G
Altcode:
  A virtual observatory with an Application Programming Interface
  (API) can become a powerful tool in analysis and modeling. In
  particular, an API that integrates time selection on such criteria
  as "most recent" and closest to a given absolute time simplifies the
  user-end programming considerably. We examine three types of use cases
  (nowcasting, data assimilation input, and user-defined sampling rates)
  for such functionality in the Virtual Solar Observatory (VSO).

Title: Design Considerations for Data Catalogs
Authors: Hourcle, J.; Suarez-Sola, I.; Davey, A.; Tian, K.; Yoshimura,
   K.; Martens, P.; Gurman, J.; Hill, F.; Bogart, R.
Bibcode: 2007AGUFMSH51A0261H
Altcode:
  Mission data catalogs are typically built with the specific mission in
  mind. This can create challenges when trying to abstract the metadata
  to make it useful to other researchers. The deluge of data from new
  missions such as STEREO and Hinode have brought in not only issues
  in scale, but also complexities due to the difference in these new
  experiments in the context of existing norms. We will discuss issues
  and use cases to be considered in designing a mission's data systems
  in order to better serve the Heliospheric community.

Title: Numerical Simulations of Power Law Heating Functions for
Quiescent Loops: Stability and Observables
Authors: Martens, P. C.; Winter, H. D.; Munetsi-Mugomba, K.
Bibcode: 2007AGUFMSH53A1053M
Altcode:
  We present the numerical simulations of quiescent coronal loops
  with heating functions that are power law functions of pressure and
  temperature. These simulations are made using a time-dependent,
  1D hydrodynamics code with heating functions that are treated as
  dynamic variables which are constantly re- evaluated during the loops'
  lifetimes. These numerical simulations provide a stability test for
  the analytical solutions formulated by Martens (2007, submitted) for
  the same heating functions. TRACE and XRT datasets are simulated to
  determine if present observables can provide adequate information to
  discriminate between power law heating functions.

Title: Dealing with Large Dataset Queries in the Virtual Solar
    Observatory
Authors: Suarez-Sola, F. I.; Bogart, R.; Davey, A.; Gurman, J. B.;
   Hill, F.; Hourcle, J.; Martens, P. C.; Tian, K.; Yoshimura, K.
Bibcode: 2007AGUFMSH51A0260S
Altcode:
  The Virtual Solar Observatory (VSO) project presents a solution for
  dealing with large dataset queries. One of the main problems arising
  from the VSO user community has been managing queries that generate
  a large amount of metadata records spanning several providers. Until
  now the only way to do this was through painstakingly repeating the
  same query for smaller time periods and collecting the information
  at each pass. With the solution presented here we are making possible
  for users to access data over any arbitrary time period in one single
  query, minimizing the metadata generated, and yet allowing the user
  to sample either a small subset or the whole.

Title: Flare Loop Top Sources: A diagnostic for non-thermal particle
    injection
Authors: Winter, H. D.; Martens, P. C.
Bibcode: 2007AGUFMSH53A1054W
Altcode:
  X-ray emitting sources have often been observed at the apex
  of post-flare loops by the Hard X-Ray telescope (HXT) onboard the
  Japanese Yohkoh satellite and by NASA's Reuven Ramaty High Energy Solar
  Spectroscopic Imager (RHESSI). In order to investigate the physics
  behind the generation of these loop top sources we have coupled a
  1D, time-dependent, hydro code with a non-thermal particle transport
  code. The hydro code provides temperature and density information of the
  target plasma to the particle code and the particle code provides the
  dynamic heating of the plasma to the hydro code. Previous work with a
  combined has shown that it is possible to create flare loop top emission
  sources under certain conditions. In this work we test the relationship
  between the pitch angle distribution of the injected non-thermal
  particles and the generation of loop top emission source. RHESSI,
  HXT and XRT datasets are synthesized from the simulations to provide
  a direct link between theoretical work and observables. This work is
  supported by NASA grant NAG5-12820.

Title: Combining Hydrodynamics Modeling with Test Particle Tracking
    to Improve Flare Simulations
Authors: Winter, H. T.; Martens, P.; Rettenmayer, J.
Bibcode: 2007ASPC..369..501W
Altcode:
  Accurate simulations of solar flares require accurately modeling of
  both the thermal and non-thermal particle distributions. Most current
  flare models concentrate on the evolution of the non-thermal particle
  distributions while treating the thermal plasma as static. In order
  to improve flare simulations Montana State University has developed
  simulation codes that couple the evolution of the non-thermal particle
  distribution and the thermal plasma of a flare in a self-consistent
  manner.

Title: Temperature Structure of Active Region Coronal Loops as seen
    by Hinode
Authors: Scott, Jason; Winter, H.; Cirtain, J.; Martens, P. C.;
   McKenzie, D.
Bibcode: 2007AAS...210.9437S
Altcode: 2007BAAS...39..327S
  We present preliminary results from Hinode of coronal loops. MSU's
  SEMAST code is used to perform differential emission measure analysis
  along active region coronal loops. The differential emission measures
  are then used to investigate the temperature and density structure
  of the loops. The results are then entered into the coronal loop
  database and compared to theoretical models for scaling laws and
  heating mechanisms. <P />This work is supported by NASA GSRP fellowship
  NNG05GK64H

Title: Analytical Solutions for Non-uniformly Heated Coronal Loops:
    Numerical Verification
Authors: Martens, Petrus C.; Winter, H. D.; Munetsi-Mugomba, K.
Bibcode: 2007AAS...210.9434M
Altcode: 2007BAAS...39..223M
  At last year's SPD meeting at UNH I presented purely analytical
  solutions for the temperature structure and scaling laws in static
  coronal loops of uniform pressure, for physically motivated heating
  functions that varied from mostly footpoint heating, via distributed
  heating, to mostly looptop heating. <P />We have verified these
  solutions with an adaptive grid 1D hydrodynamic loop code, and found
  that for most heating profiles our analytical solutions are in agreement
  with the numerical ones within a few percent. This result is remarkable
  since the analytical solutions implied some drastic simplifications for
  the radiative loss function and the boundary conditions. We also found
  that when the heating is concentrated too strongly at the footpoints
  static solutions no longer exist and the loop remains dynamic. This
  confirms earlier results by Mueller and Karpen. <P />Our results
  imply that it is now very easy to construct Differential Emission
  Measures (DEMs) for loops consisting of a bundle of elementary strands,
  and compare these DEMS with those of actually observed loops through
  forward folding. We will apply this method to joint TRACE, Hinode-XRT,
  and EIS data.

Title: Science With the Virtual Solar Observatory: Today and Tomorrow
Authors: Hill, F.; Bogart, R. S.; Davey, A. R.; Gurman, J. B.; Hourcle,
   J. A.; Martens, P. C.; Reardon, K. M.; Suarez-Sola, I.; Tian, K. Q.;
   Yoshimura, K.
Bibcode: 2007AGUSMSM33D..05H
Altcode:
  The Virtual Solar Observatory (VSO) was released to the community in
  December 2004. It is designed to provide solar physicists with a tool
  that allows them to locate and access solar data in an efficient manner,
  thus facilitating science studies involving multiple data sets. Examples
  of science projects that have been done with the VSO are a study of
  halo CME speeds and their visibility in a variety of SOHO data sets,
  and the calibration between helioseismic farside signals and the
  characteristics of active regions. Future possible projects include
  studies of farside coronal mass ejections; the relationship between
  subsurface flows and solar wind speeds; statistics of the active region
  life cycle; sunspot energetics, and space weather predictors.

Title: The Stars as Suns Project: Recent Results from Solar and
    Stellar Dynamo Modeling
Authors: Munoz, Andres; Nandy, D.; Martens, P. C.
Bibcode: 2007AAS...210.9209M
Altcode: 2007BAAS...39..210M
  Solar variability controls our space environment and is also believed
  to play a role in shaping the global climate. The variability of the Sun
  can be traced back to the presence and modulation of magnetic fields --
  which has its origin in a dynamo mechanism working in the interior. The
  "Stars as Suns" project aims to determine the long-term variability of
  Sun, through a combination of stellar magnetic activity observations
  of Sun-like stars and theoretical dynamo modeling. Here we present
  recent results from solar and stellar dynamo studies that addresses
  the goals of this project. This research is funded by a NASA Living
  With a Star grant NNG05GE47G to Montana State University.

Title: Long-Term Evolution of Solar Magnetic Activity Derived From
    Stellar Proxies
Authors: Nandy, D.; Martens, P. C.
Bibcode: 2007AGUSMSH54B..04N
Altcode:
  The variability of the Sun over stellar and planetary evolutionary
  timescales may have important consequences for planetary atmospheres
  such as the Earth's, including the forcing of global climate and
  evolution of life. This solar variability is in part due to the
  changing magnetism of the Sun, which has origins in the solar dynamo
  mechanism. A novel approach towards determining solar variability
  over such long timescales - stretching to billions of years - is
  to use Sun-like stars in various evolutionary phases as proxies of
  solar activity. In this talk, I will review efforts to derive this
  long-term variability of the Sun through theoretical dynamo modelling
  and observational analysis of stellar magnetic activity. This work is
  funded by the NASA Living With a Star program through grant NNG05GE47G.

Title: Online Catalog for Filament-Sigmoid Correlation
Authors: Merriot, Ivy; Pevtsov, A.; Martens, P.
Bibcode: 2007AAS...210.9504M
Altcode: 2007BAAS...39..224M
  A new online catalog correlating H-alpha filaments with SXT sigmoids
  gives researchers, teachers and pre-college students the ability to
  access digital H-alpha images online that were previously available
  only at the physical location of the NSO at Sunspot, NM. This web-based
  catalog correlates SOHO's SXT sigmoids from 1993-1998 as described
  in a non-online catalog created by Zach Blehm under the direction
  of Richard Canfield, MSU-Bozeman, with H-alpha filament activity as
  described by Ivy Merriot under the direction of Alexei Pevtsov, NSO,
  and Petrus Martens, MSU-Bozeman. The H-alpha images were digitized
  from film archives of the Flare Patrol Telescope at Sunspot, NM. Use
  of the online catalog will be demonstrated at the poster site with
  critical comments encouraged.

Title: On-orbit Measurement Of The Hinode/XRT Point Spread Function
Authors: Weber, Mark A.; Cirtain, J.; Golub, L.; DeLuca, E. E.;
   Martens, P.; XRT Team
Bibcode: 2007AAS...210.9416W
Altcode: 2007BAAS...39..220W
  The Hinode X-Ray Telescope provides unprecedented observations of
  the solar corona in x-rays, due in part to its fine resolution. The
  optical point spread function (PSF) was measured before launch at the
  NASA X-Ray Calibration Facility to have a FWHM of 0.92 arc-seconds. In
  this poster we describe our work to verify the PSF measurements using
  on-orbit data. The US XRT team is supported by a contract from NASA to
  SAO. Hinode is an international project supported by JAXA, NASA, PPARC,
  and ESA. We are grateful to the Hinode team for all their efforts in
  the design, development, and operation of the mission.

Title: Low Cost X-ray Optics for Studying StellarDynamo Cycles
Authors: Rust, Thomas; Acton, L.; Kankelborg, C.; Martens, P.
Bibcode: 2007AAS...210.2302R
Altcode: 2007BAAS...39..128R
  Comparison of measured coronal X-ray variability over stellar magnetic
  dynamo cycles with theoretical models will yield new understanding
  of the solar magnetic dynamo cycle. We present the results of a study
  comparing surface roughnesses of three candidate materials for use as
  glancing angle X-ray reflectors. This work is part of a continuing
  effort by MSU's Solar Physics Group and Space Science Engineering
  Laboratory (SSEL) to design and build large aperture, low cost X-ray
  optics for space experiments. The MSU proposed SADE (Starspot and
  Dynamo Explorer) instrument would use arrays of nested Kirkpatrick-Baez
  reflectors, called STAX (Sade Telescope Array for X-rays), for long
  term measurements of soft X-ray fluxes from about a hundred nearby
  solar-type stars. The advantage of the STAX design is that it uses
  "off the shelf" materials bent to shape, which is far cheaper and
  easier to manufacture than the polished cylindrical optics typically
  used in X-ray telescopes. In order to determine whether off the shelf
  materials satisfy the stringent surface smoothness requirements for
  glancing angle reflectors, we have undertaken an atomic force microscope
  investigation of three candidate <P />materials. In addition, we compare
  the measured and theoretical diffraction pattern of our existing STAX
  test article. This comparison will provide insight into the suitability
  of the candidate material, as well as the feasibility of maintaining
  proper shape over the surface of the reflector by constraining the
  edges in precision machined grooves. This work is supported by a grant
  from MSU/NASA EPSCOR.

Title: The REU Program in Solar Physics at Montana State University
Authors: Martens, Petrus C.; Canfield, R. C.; McKenzie, D. M.
Bibcode: 2007AAS...210.8012M
Altcode: 2007BAAS...39Q.189M
  The Solar Physics group at Montana State University has organized
  an annual summer REU program in Solar Physics, Astronomy, and Space
  Physics since 1999, with NSF funding since 2003. The number of
  students applying and being admitted to the program has increased
  every year, and we have been very successful in attracting female
  participants. A great majority of our REU alumni have chosen career
  paths in the sciences, and, according to their testimonies, our REU
  program has played a significant role in their decisions. From the
  start our REU program has had an important international component
  through a close collaboration with the University of St. Andrews in
  Scotland. <P />In our poster we will describe the goals, organization,
  scientific contents, international aspects, and results, and present
  statistics on applications, participants, gender balance, and diversity.

Title: Active Region Loops: Temperature Measurements as a Function
    of Time from Joint TRACE and SOHO CDS Observations
Authors: Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.;
   Martens, P. C. H.; Schmelz, J. T.
Bibcode: 2007ApJ...655..598C
Altcode:
  In this paper, we aim to quantitatively investigate the structure
  and time variation of quiescent active region loop structures. We
  coordinated a joint program of observations (JOP 146) using TRACE, to
  obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic
  data. Loop intensities are used to determine temperature as a function
  of time for a single loop, taking full account of the background
  emission. In many locations, the emission measure loci are consistent
  with an isothermal structure. However, the results indicate significant
  changes in the loop temperature (between 1 and 2 MK) over the 6 hr
  observing period. It is possible that the loop structures are composed
  of multiple, independently heated strands with sizes less than the
  resolution of the imager and spectrometer.

Title: Space Climate and the Solar Stellar connection: What can we
    learn from the stars about long-term solar variability?
Authors: Nandy, Dibyendu; Martens, P. C. H.
Bibcode: 2007AdSpR..40..891N
Altcode:
  While it is well-known that solar variability influences the
  near-Earth Space environment at short timescales of days - an effect
  collectively termed as Space Weather, a more subtle influence of solar
  variability at longer timescales is also present and just beginning to
  be appreciated. Long-term solar forcing and its consequences - which has
  come to be known as Space Climate - has important consequences for the
  formation and evolution of planetary atmospheres, the evolution of life
  and global climate on Earth. Understanding the Sun's variability and
  its heliospheric influence at such scales, stretching from decennia
  to stellar and planetary evolutionary timescales, is therefore of
  fundamental importance. However, our knowledge of this variability,
  which is in part due to the evolution of the solar magnetic dynamo,
  is limited by direct solar observations which exist only from early
  17th Century onwards. In this review we introduce a novel concept -
  how the Solar-Stellar connection can be exploited to understand the
  long-term variability of the Sun and its influence on Space Climate. We
  present some preliminary studies, in which, through theoretical dynamo
  modeling and analysis of magnetic activity observations of solar-like
  stars at various evolutionary phases relative to the Sun, we show how
  the above concept is implemented in practice.

Title: The Trace Telescope Point Spread Function for the 171 Å Filter
Authors: Gburek, S.; Sylwester, J.; Martens, P.
Bibcode: 2006SoPh..239..531G
Altcode: 2006SoPh..tmp...76G
  We perform an analysis of the TRACE telescope blur from EUV
  images. Theblur pattern is discussed in terms of the telescope
  point-spread function (PSF) for the 171 Å filter. The analysis
  performed consists of two steps. First, an initial shape for the
  PSF core is determined directly from TRACE EUV images. Second,
  the blind-deconvolution method is used for obtaining the final PSF
  shape. The PSF core peak is fitted by analytical functions to determine
  its parametric characteristics. The determined PSF includes the core
  central peak and peaks caused by diffraction effects inherent in TRACE
  EUV data. The diffraction portion of the PSF is studied theoretically
  in the Fraunhofer diffraction limit. The temperature dependence of the
  TRACE PSF shape is investigated for a selected temperature range. We
  also discuss general properties of the obtained PSF and its possible
  applications.

Title: The current and future roles of virtual observatories serving
    the heliophysical data environment
Authors: Davey, A. R.; Bogart, R. S.; Dimitoglou, G.; Gurman, J. B.;
   Hill, F.; Hourcle, J. A.; Martens, P. C.; Suarez-Sola, I.; Tian, K.;
   Yoshimura, K.
Bibcode: 2006AGUFMSM11C..05D
Altcode:
  The Virtual Solar Observatory is just one of a growing number of
  virtual observatories that serve heliophysics data. We discuss the
  current capabilities of these virtual observatories, their roles in
  data archiving, discovery, quality assurance, assimilation, encouraging
  standards and in facilitating science. We also discuss the realistic
  goals virtual observatories should have, in fulfilling the demands of
  the current and near future heliophysics data environment.

Title: Simulation of Hard X-ray Looptop Sources in Solar Flares
Authors: Winter, H. D.; Martens, P. C.
Bibcode: 2006AGUFMSH23A0332W
Altcode:
  Many solar flares show a non-thermal X-ray emitting source at the
  apex of the post-flare loop. This behavior has been observed both by
  the Hard X-Ray telescope (HXT) on board the Japanese Yohkoh satellite
  and by NASA's Reuven Ramaty High Energy Solar Spectroscopic Imager
  (RHESSI). By combining thermal plasma and non-thermal particle numerical
  models we are able to simulate thermal and non-thermal flare emission
  under a variety of increasingly realistic solar conditions. We find
  that looptop sources can be generated by a combination of magnetic
  mirroring of non-thermal particles and heated chromospheric material
  flowing upward from both legs of the loop. In this work we inject
  non-thermal, energetic particles with varying pitch angle distributions
  and spectral indices into plasmas contained in loops defined by an
  analytical magnetic field model. We monitor the evolution of these
  loops over time as it would be seen by HXT and RHESSI and compare
  the simulated emission to observations of flare loops. This work is
  supported by NASA grant NAG5-12820.

Title: The Virtual Solar Observatory and the Heliophysics Meta-Virtual
    Observatory
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
   Hill, F.; Suàrez-Sola, I.; Zarro, D. M.; Davey, A. R.; Martens,
   P. C.; Yoshimura, K.; Reardon, K. M.
Bibcode: 2006AGUFMSM21A0246G
Altcode:
  The Virtual Solar Observatory (VSO) has survived its infancy and
  provides metadata search and data identification for measurements from
  45 instrument data sets held at 12 online archives, as well as flare
  and coronal mass ejection (CME) event lists. Like any toddler, the VSO
  is good at getting into anything and everything, and is now extending
  its grasp to more data sets, new missions, and new access methods
  using its application programming interface (API). We discuss and
  demonstrate recent changes, including developments for STEREO and SDO,
  and an IDL-callable interface for the VSO API. We urge the heliophysics
  community to help civilize this obstreperous youngster by providing
  input on ways to make the VSO even more useful for system science
  research in its role as part of the growing cluster of Heliophysics
  Virtual Observatories.

Title: Stars as Suns: Unravelling Long-term Solar Variability by
    Stellar Dynamo Modeling
Authors: Martens, P. C.; Nandi, D.; Munoz, A.
Bibcode: 2006AGUFMSH21B..03M
Altcode:
  We have developed a very time-efficient 2.5 D dynamo code to carry out
  simulations of stars that are very similar, but not identical to the
  Sun. The main goal is to better understand the nature and evolution
  of the solar dynamo by studying how its main characteristics (period,
  activity level) vary within the parameter space close to the observed
  or assumed input parameters and profiles that reproduce the solar
  dynamo, and by comparing these results with the periods, X-ray and
  Ca HK activity levels, that are known for many Sun-like stars. In
  particular we will carry out simulations for both the Babcock-Leighton
  (surface) and the mean field (convection zone) alpha-effect to determine
  which one better reproduces the dynamo periods and activity levels of
  Sun-like stars, and thereby is the more likely mechanism operating
  in stellar (and solar) dynamos. The relevance of this work is that
  a better understanding of the evolution of the dynamo mechanism will
  enable us to make more confident predictions for the Sun's variability
  spanning from solar cycle-like timescales to stellar evolutionary
  timescales. This will provide more reliable input for space weather
  and Earth's climate forecasters and increases our understanding of
  the long term evolution of the Sun's magnetic field and its subsequent
  effect on the Sun-Earth connection.

Title: A Time Delay Model for Solar and Stellar Dynamos
Authors: Wilmot-Smith, A. L.; Nandy, D.; Hornig, G.; Martens, P. C. H.
Bibcode: 2006ApJ...652..696W
Altcode:
  Magnetohydrodynamic dynamos operating in stellar interiors produce
  the diverse range of magnetic activity observed in solar-like
  stars. Sophisticated dynamo models including realistic physics of
  convection zone flows and flux tube dynamics have been built for
  the Sun, for which appropriate observations exist to constrain such
  models. Nevertheless, significant differences exist in the physics that
  the models invoke, the most important being the nature and location
  of the dynamo α-effect and whether it is spatially segregated from
  the location of the Ω-effect. Spatial segregation of these source
  layers necessitates a physical mechanism for communication between
  them, involving unavoidable time delays. We construct a physically
  motivated reduced dynamo model in which, through the use of time delays,
  we mimic the generation of field components in spatially segregated
  layers and the communication between them. The model can be adapted
  to examine the underlying structures of more complicated and spatially
  extended numerical dynamo models with diverse α-effect mechanisms. A
  variety of dynamic behaviors arise as a direct consequence of the
  introduction of time delays in the system. Various parameter regimes
  give rise to periodic and aperiodic oscillations. Amplitude modulation
  leads to episodes of reduced activity, such as that observed during
  the Maunder minima, the length and duration of which depend on the
  dynamo number. Regular activity is more easily excited in the flux
  transport-dominated regime (when the time delay is smaller than the
  dissipative timescale), whereas irregular activity characterizes
  solutions in the diffusion-dominated regime (when the time delay is
  larger than the dissipative timescale).

Title: Unravelling Long-Term Solar Variability: The Stars As Suns
    Project
Authors: Nandy, D.; Martens, P. C. H.
Bibcode: 2006IAUJD...8E..13N
Altcode:
  It is well known that solar variability influences the near-Earth
  Space environment at short timescales of days - an effect collectively
  termed as Space Weather. A lesser known and more subtle influence of
  solar variability at longer timescales, is however, just beginning
  to be appreciated. This long-term solar forcing, which is sometimes
  referred to as Space Climate, has important consequences for the
  formation and evolution of planetary atmospheres, evolution of life
  and global climate on Earth. Understanding the Sun's variability and
  its heliospheric influence at such scales stretching from millennia
  to stellar evolutionary timescales is therefore of fundamental
  importance. However, our understanding of this variability, which is
  partly due to the evolution of the solar magnetic dynamo, is limited by
  solar observations which exist only from early 17^th Century onwards. In
  this talk I will review the "Stars as Suns" project - in which we
  take a novel approach to unravelling long-term solar variability
  through theoretical modelling and magnetic activity observations of
  Sun-like stars, which are at various evolutionary phases relative to
  the Sun. The "Stars as Suns" project is funded by the NASA Living With
  a Star program through grant NNG05GE47G.

Title: A Surprising New Take on Scaling Laws
Authors: Martens, Petrus C.
Bibcode: 2006SPD....37.1705M
Altcode: 2006BAAS...38R.246M
  I have derived analytical solutions for the 1D energy equation for
  static solar coronal loops for a set of heating functions parametrized
  as power-laws. This formalism yields a large set of solutions including
  loops that are mainly heated at the footpoints, at the looptop, and
  uniformly. I found that the analytical solutions are indistinguishable
  from numerical solutions produced the MSU 1D hydro-code.I also find that
  there is very little difference between the temperature profiles for
  these very different heating functions. A surprising result is though
  that the constant of proportionality in the classic RTV scaling law
  (PL T^3) depends strongly on the heating function used, yielding a
  potential diagnostic for the type of heating function at work in the
  solar corona -- assuming most loops have the same heating profile. Loops
  heated at the base have a large constant of proportionality, leading to
  overdense loops compared to the case of uniform heating, and v.v. for
  loops heated at the top -- an effect that had already been noticed
  in numerical solutions but has been inaccurately been interpreted
  as a violation of the scaling law.This work is supported by NASA
  Grant NAS5-38099 for the Transition Region and Coronal Explorer, and
  NNG04EA00C for the Atmospheric Imaging Assembly through subcontracts
  with Lockheed-Martin Solar and Astrophysics Lab.

Title: Implementation of an Exponential Propagation Method to
    Numerically Solving the 2.5 D Stellar Dynamo Equations
Authors: Munoz, Andres; Martens, P. C.; Nandy, D.
Bibcode: 2006SPD....37.1202M
Altcode: 2006BAAS...38Q.240M
  Magnetic fields in stars such as the Sun originate via a MHD dynamo
  mechanism working in their interior. A complete understanding of the
  dynamo mechanism, which involves complex and non-linear interactions
  between plasma flows and magnetic fields, remains an elusive and
  outstanding problem in Astrophysics. As an integral step in a study of
  stellar dynamos, part of a new MSU project entitled "Stars as Suns:
  Unraveling Long-term Solar Variability by Stellar Dynamo Modeling",
  a numerical solution for the 2D dynamo equations is being developed
  that uses an exponential propagation method, in which, the exponential
  is approximated using a projection into a Krylov subspace. As has
  been found in other work, this kind of numerical scheme presents a
  promising alternative to explicit schemes, since it is not subject
  to the CFL condition, and to implicit methods, since an iteration
  using the projection onto a Krylov subspace converges faster than an
  equivalent solution of the implicit formulation. Here, we outline our
  preliminary efforts towards developing this new numerical scheme for
  addressing the stellar dynamo problem.This research is supported by
  NASA Grant NNGO5GE47G to MSU.

Title: Testing the Methods Used to Determine Loop Temperature Profiles
Authors: Neal, Kerry; Winter, H. D.; Martens, P. C.
Bibcode: 2006SPD....37.0113N
Altcode: 2006BAAS...38..217N
  Determining the heating profile of coronal loops is still a fundamental
  problem in solar physics. In order to determine the heating profile of
  three candidate loops we measure their temperature profiles by employing
  multiple techniques; filter ratios, line ratios, emission measure
  (EM) loci and differential emission measure (DEM) analysis. We find
  that the temperature responses are largely influenced by the method of
  analysis employed. We compare the accuracy of these methods by creating
  simulations of known heating profiles along loops and repeat the methods
  of analysis that were used on the observed loops. In the numerical
  models the line of sight and ionization non-equilibrium effects can
  be taken into account and their effects on temperature measurement
  demonstrated. Results from the upcoming Atmospheric Imaging Assembly
  are also simulated in preparation for the upcoming mission.This work
  was sponsored by NASA GSFC Contract NNG04EA00C for the Atmospheric
  Imaging Assembly and NSF REU grant ATM-0243923.

Title: Coronal Loop Database
Authors: Scott, Jason; Martens, P.
Bibcode: 2006SPD....37.0120S
Altcode: 2006BAAS...38R.218S
  We have created a database of all coronal loops for which we have been
  able to find measurements in the published open literature, from Skylab
  to TRACE. The loops and a set of their physical parameters are stored
  in the form of an IDL structure. The physical parameters considered
  are: the loop half length, the electron density of the loop, and the
  loop temperature. The studies that produced the physical parameters
  along with their observing instruments are recorded in the database
  as well. Correlations of pressure vs. temperature and heating rates
  vs. loop length are investigated. Instrumental selection effects are
  also considered. The loop parameters and correlations derived from the
  loop database are then compared to theoretical and numerical models
  for scaling laws and heating rates.This work is supported by NASA GSRP
  fellowship NNG05GK64H

Title: The Hi-C Sounding Rocket Experiment
Authors: Golub, Leon; Cirtain, J.; DeLuca, E.; Nystrom, G.; Kankelborg,
   C.; Klumpar, D.; Longcope, D.; Martens, P.
Bibcode: 2006SPD....37.0605G
Altcode: 2006BAAS...38R.226G
  The High-resolution Coronal Imager, Hi-C, is a pathfinder
  mission designed to place significant new limits on theories of
  coronal heating and dynamics by measuring the structures at size
  scales relevant to reconnection physics. The Hi-C instrument uses
  normal-incidence EUV multilayer technology, as developed in the
  NIXT and TRACE programs. A dual-channel long focal-length telescope
  and large format back-illuminated CCD camera provide spectroscopic
  imaging of the corona at 0.1 arcsec resolution.The main objective of
  the Hi-C investigation is to determine the geometric configuration and
  topology of the structures making up the inner corona. The secondary
  objective is to examine the dynamics of those structures, within the
  constraints of the 300-seconds of observing time available from a
  sounding rocket. The mission is designed to study the mechanisms for
  growth, diffusion and reconnection of magnetic fields, and to help
  understand the coupling of small-scale dynamic and eruptive processes
  to large-scale dynamics.Hi-C will benefit from a unique coordinated
  observation opportunity with investigations such as AIA on SDO, XRT on
  Solar-B, and STEREO. Hi-C will address basic plasma physics science
  goals of the SSSC by observing the small-scale processes that are
  ubiquitous in hot magnetized coronal plasma. The scientific objectives
  of Hi-C are central to the SSSC goal of understanding the Sun's activity
  and its effects on the terrestrial environment, by providing unique
  and unprecedented views of the dynamic activity in the solar atmosphere.

Title: The Virtual Solar Observatory and the Heliophysics Meta-Virtual
    Observatory
Authors: Gurman, Joseph B.; Bogart, R.; Tian, K.; Hill, F.;
   Suárez-Sola, I.; Martens, P. C.; Yoshimura, K.; Davey, A.; Dimitoglou,
   G.; Hourclé, J.
Bibcode: 2006SPD....37.0305G
Altcode: 2006BAAS...38..222G
  The Virtual Solar Observatory (VSO) is now able to search for solar
  data ranging from the radio to gamma rays, obtained from space and
  groundbased observatories, from 26 sources at 12 data providers, and
  from 1915 to the present. The solar physics community can use a Web
  interface or an Application Programming Interface (API) that allows
  integrating VSO searches into other software, including other Web
  services. Over the next few years, this integration will be especially
  obvious as the NASA Heliophysics division sponsors the development of
  a heliophysics-wide virtual observatory (VO), based on existing VO's
  in heliospheric, magnetospheric, and ionospheric physics as well as
  the VSO. We examine some of the challenges and potential of such a
  "meta-VO."

Title: Multi-Instrument Simulations of Solar Flares Using Non-Thermal
    Particle Tracking
Authors: Winter, Henry D., III; Martens, P. C.
Bibcode: 2006SPD....37.1313W
Altcode: 2006BAAS...38..242W
  We are combining thermal plasma and non-thermal particle numerical
  models in order to improve flare simulations. Non-thermal particle
  collision models provide heating and momentum deposition for the
  thermal plasma. The thermal plasma models in turn provide an evolving
  temperature and density structure for the non-thermal particles'
  target plasma. This allows us to simulate thermal and non-thermal flare
  emission under a variety of increasingly realistic solar conditions. In
  this work we inject non-thermal, energetic particles into plasmas
  contained in loops defined by three different analytic magnetic field
  models. We monitor the evolution of these loops over time as it would
  be seen by the Reuven Ramaty High Energy Solar Spectroscopic Imager
  (RHESSI), The Transition Region and Coronal Explorer (TRACE), the
  Soft X-ray Telescope (SXT) and the Hard X-ray Telescope (HXT) onboard
  the Yohkoh satellite as well as the upcoming X-Ray Telescope (XRT)
  onboard Solar-B and the Atmospheric Imaging Array (AIA) on the Solar
  Dynamics Observatory.This work is supported by NASA grant NAG5-12820.

Title: The VSO at Two and a Half
Authors: Gurman, J. B.; Hourclé, J. A.; Bogart, R. S.; Tian, K.;
   Hill, F.; Suarez-Sola, I.; Wampler, S.; Davey, A. R.; Martens, P. C.;
   Yoshimura, K.; Zarro, D. M.
Bibcode: 2006AGUSMSM31B..03G
Altcode:
  The Virtual Solar Observatory (VSO) has survived its infancy and
  provides metadata search and data identification for 26 data sets
  held at 12 online archives, as well as flare and coronal mass ejection
  (CME) event lists. Like any toddler, the VSO is good at getting into
  anything and everything, and is now extending its grasp to more data
  sets and providers, new missions, and new access methods using its
  application programming interface (API). We discuss recent changes,
  including developments for STEREO and SDO, and an IDL-callable interface
  for the VSO API. We urge the heliophysics community to help civilize
  this obstreperous youngster by providing input on ways to make the
  VSO even more useful for system science research.

Title: The EUV Unresolved Corona
Authors: Cirtain, Jonathan; Martens, P. C. H.; Acton, L. W.; Weber,
   Mark
Bibcode: 2006SoPh..235..295C
Altcode:
  The unresolved corona for three active regions (ARs) above the solar
  limb is investigated. Intensities measured for ions formed above 1 MK
  are presented as a function of height above the solar surface. The
  observed decrease in intensity with altitude is found to be best
  fit by an exponential. Furthermore, this exponential decrease is
  approximately the decrease in emission expected for a hydrostatic
  planar geometry atmosphere, where the scale height temperature is
  dependent on the dynamics of the AR. For two of the ARs analyzed, we
  have found that the best-fit temperature derived from the exponential
  fits is consistent with an isothermal hydrostatic unresolved corona.

Title: Unraveling long-term solar variability and its impact on
space climate: The stars as suns project
Authors: Nandy, D.; Martens, P. C. H.
Bibcode: 2006ilws.conf..158N
Altcode:
  It is well-known that solar variability influences the near-Earth
  Space environment at short timescales of days - an effect collectively
  termed as Space Weather. A lesser known and more subtle influence of
  solar variability at longer timescales is however just beginning to be
  appreciated. This long-term solar forcing, which is sometimes referred
  to as Space Climate, has important consequences for the formation
  and evolution of planetary atmospheres and the evolution of life and
  global climate on Earth. Understanding the Sun's variability and its
  heliospheric influence at such scales stretching from millennia to
  stellar evolutionary timescales is therefore of fundamental importance
  and a very promising area of future research. However, our understanding
  of this variability, which is in part connected to the evolution of the
  solar magnetic dynamo, is limited by continuous sunspot observations,
  which exist only from the early 17th Century onwards. In this paper we
  review the "Stars as Suns" project - in which we take a radically new
  approach to unraveling long-term solar variability through theoretical
  modeling and magnetic activity observations of Sun-like stars, which
  are at various evolutionary phases relative to the Sun.

Title: Multithermal Analysis of a SOHO/CDS Coronal Loop
Authors: Schmelz, J. T.; Martens, P. C. H.
Bibcode: 2006ApJ...636L..49S
Altcode: 2005astro.ph.11487S
  The observations from 1998 April 20 taken with the Coronal Diagnostics
  Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) of
  a coronal loop on the limb have shown that the plasma was multithermal
  along each line of sight investigated, both before and after background
  subtraction. The latter result relied on emission measure (EM) loci
  plots, but in this Letter, we used a forward-folding technique to
  produce differential emission measure (DEM) curves. We also calculate
  DEM-weighted temperatures for the chosen pixels and find a gradient
  in temperature along the loop as a function of height that is not
  compatible with the flat profiles reported by numerous authors for
  loops observed with the EUV Imaging Telescope (EIT) on SOHO and
  the Transition Region and Coronal Explorer (TRACE). We also find
  discrepancies in excess of the mathematical expectation between some
  of the observed and predicted CDS line intensities. We demonstrate
  that these differences result from well-known limitations in our
  knowledge of the atomic data and are to be expected. We further show
  that the precision of the DEM is limited by the intrinsic width of
  the ion emissivity functions that are used to calculate the DEM, which
  for the EUV lines considered is of the order dlogT = 0.2-0.3. Hence,
  we conclude that peaks and valleys in the DEM, while in principle not
  impossible, cannot be confirmed from the data.

Title: The virtual solar observatory
Authors: Young, C. A.; Gurman, J. B.; Dimitoglou, G.; Hourcle, J.;
   Bogart, R. S.; Tian, K.; Hill, F.; Suarz-Sola, I.; Wampler, S.;
   Martens, P.; Yoshimura, S.; Davey, A.
Bibcode: 2006ilws.conf..226Y
Altcode:
  The recent explosion of data quantity and complexity has lead to the
  need for a new way to make data available, the virtual observatory. The
  Virtual Solar Observatory (VSO) provides a versatile means for solar
  physicists to discover and share the growing sources of data. We present
  the development of the VSO, show the system in action and discuss how
  data users and data providers can benefit from it.

Title: TRACE and SXT Responses to Flare Simulations Using Combined
    Non-Thermal Particle and Hydrodynamic Modeling
Authors: Winter, H. D.; Martens, P.; Rettenmayer, J.
Bibcode: 2005AGUFMSH13A0296W
Altcode:
  Thermal plasma and non-thermal particle numerical models are combined
  in order to improve flare simulations. The non-thermal particle
  collision models provide heating and momentum deposition for the
  thermal plasma. The thermal plasma models in turn provide an evolving
  temperature and density structure for the non-thermal particles target
  plasma. This allows for the simulation of thermal and non-thermal flare
  emission under a variety of increasingly realistic solar conditions. The
  model flare emission is then folded through the response functions of
  solar observatories in order to provide simulated data that can be
  compared to observational results. Using this technique, Transition
  Region and Coronal Explorer (TRACE) and Soft X-ray Telescope (SXT)
  simulations are made. This provides a means to verify the predictions
  of multiple flare models with observed flare behavior. This work is
  supported by NASA grant NAG5-12820

Title: Flare Prediction and the Unresolved Corona
Authors: Weber, M.; Cirtain, J.; Martens, P.
Bibcode: 2005AGUFMSH13A0280W
Altcode:
  Discovery of the precursors to flare onset are paramount to the
  increased need for accurate space weather prediction. A potential
  indicator for flaring activity may be the temperature structure of
  the active region background emission. The active region background,
  or unresolved active region corona (UARC), can be modeled using a
  hydrostatic model for the density stratification as a function of
  altitude. Exponential decreases in the intensity of EUV emission above
  the limb and within active regions have been used to determine the
  scale-height temperature of the UARC. ``Quiescent'' active region data
  was examined, and the scale-height temperature determined was found to
  be constant in time and slowly decreasing with distance from the center
  of the active region. ``Flaring'' active region emission was found
  to be quite different. Prior to the onset of the flare, the estimated
  scale height temperature was nearly constant. Just before the peak in
  the GOES 8 x-ray flux, it was determined to be multithermal, varying
  by as much as 0.7 MK over the multiple spectral lines observed. The
  scale-height temperatures were all observed to increase before the
  flare and reached a maximum subsequent to the GOES 8 x-ray peak.This
  work is supported under the TRACE mission, NASA contract SP02H8201R.

Title: REU program in Solar Physics at Montana State University
Authors: Martens, P. C.; Canfield, R. C.; McKenzie, D. M.
Bibcode: 2005AGUFMED31A1202M
Altcode:
  I will present an overview of the REU program in Solar Physics and Space
  Weather that has existed since 1999 at Montana State University, since
  2003 with NSF support. I will briefly describe the goals, organization,
  scientific contents and results, and present statistics on applications,
  participants, gender balance, and diversity. This will be concluded
  by an overview of our plans for the future,

Title: The Amplitude of Stellar X-ray Cycles
Authors: Martens, P. C. H.; Chattterjee, P.; Saar, S. H.; Acton,
   L. W. A.
Bibcode: 2005AAS...20710405M
Altcode: 2005BAAS...37R1334M
  A decade worth of data from the Soft X-ray Telescope onboard the
  Japan/US/UK mission Yohkoh shows that the Sun has a variation of
  non-flaring disk-integrated soft X-ray emission (0.4 - 2.4 keV) of
  about a factor 30 over its sunspot cycle. To date no cyclic variation
  of that magnitude has been observed in other late-type stars. <P />We
  show that this negative result is partly explained by the inclusion of
  EUV emission in stellar observations done with ROSAT: we calculated
  what the solar signal would be if observed in the ROSAT passband and
  found a cycle amplitude of a factor two to three. That leaves open
  the question of the cycle amplitude in soft X-rays for solar-type
  stars. <P />To adress this we analysed ROSAT data for the energy band
  above the C-K edge, but found no sufficiently frequent observations of
  individual stars. The next best approach is to compare the measured soft
  X-ray flux for singly observed stars with the average flux predicted
  from the star's Rossby number: if cycles with amplitudes as large as
  that of the Sun exist, the residual fluxes should be statistically
  significant. From a sample of about 15 single and cyclic late-type
  stars (as evidenced from Ca-K data) we find that with 99.6% certainty
  the residual fluxes are due to X-ray cycles that are similar to or
  greater than that of the Sun.

Title: The Magnetic Activity of Solar-like Stars at Different
    Main-Sequence Ages
Authors: Lakatos, S. L.; Nandy, D.; Martens, P.
Bibcode: 2005AAS...20711104L
Altcode: 2005BAAS...37.1342L
  We report on a study of modeling stellar magnetic activity inferred
  through CaII H+K and ROSAT X-ray emission. The purpose of this project
  is to create a subset of stars with similar properties to the Sun,
  but with a wide range of ages (0.6 - 10 Gyrs); to study the CaII H+K
  emission data and decipher how the stars' emission changes with age;
  and to compare the X-ray activity to the CaII H+K activity. The ultimate
  goal of this project is to determine and use the relationships between
  the stellar parameters to understand the evolution of the magnetic
  dynamo from an younger Sun to an older Sun. This research is supported
  by a NSF Research Experience for Undergraduates grant ATM-0243923 and
  a NASA Living With a Star grant NNG05GE47G to Montana State University.

Title: Dynamics of Active Region Loops: Temperature Measurements as
    a function of Time
Authors: Cirtain, J. J.; del Zanna, G.; Mason, H.; Deluca, E.;
   Martens, P.
Bibcode: 2005AGUFMSH44A..03C
Altcode:
  The combination of moderate resolution EUV spectroscopy and high
  resolution narrow band filter images provides the most accurate
  measure of temperature and density for coronal loops to date. We will
  demonstrate our technique for combining the data sets from the Coronal
  Diagnostic Spectrometer on SoHO and the Transition Region and Coronal
  Explorer. Background subtracted spectral intensities are used to
  determine the temperature of coronal loops and the TRACE images help
  determine the loop cross-section, temporal variability, and filling
  factor. The resulting temperature profiles for multiple positions along
  a loop leg are determined using the EM LOCI method, and a technique for
  determining whether a single temperature can characterize the plasma is
  also presented. We compare the results of our study to current models.

Title: Low-order stellar dynamo models
Authors: Wilmot-Smith, A. L.; Martens, P. C. H.; Nandy, D.; Priest,
   E. R.; Tobias, S. M.
Bibcode: 2005MNRAS.363.1167W
Altcode: 2005MNRAS.tmp..855W
  Stellar magnetic activity - which has been observed in a diverse set
  of stars including the Sun - originates via a magnetohydrodynamic
  dynamo mechanism working in stellar interiors. The full set of
  magnetohydrodynamic equations governing stellar dynamos is highly
  complex, and so direct numerical simulation is currently out of
  reach computationally. An understanding of the bifurcation structure,
  likely to be found in the partial differential equations governing such
  dynamos, is vital if we are to understand the activity of solar-like
  stars and its evolution with varying stellar parameters such as rotation
  rate. Low-order models are an important aid to this understanding,
  and can be derived either as approximations of the governing equations
  themselves or by using bifurcation theory to obtain systems with the
  desired structure. We use normal-form theory to derive a third-order
  model with robust behaviour. The model is able to reproduce many of the
  basic types of behaviour found in observations of solar-type stars. In
  the appropriate parameter regime, a chaotic modulation of the basic
  cycle is present, together with varying periods of low activity such
  as that observed during the solar Maunder minima.

Title: Improving Flare Simulations by Combining Hydrodynamics Modeling
    with Stochastic Particle Transport
Authors: Winter, H. T.; Martens, P.
Bibcode: 2005AGUSMSP21A..11W
Altcode:
  Currently flare models include heating due to non-thermal particle
  collisions as analytical, and often static, inputs to numerical
  hydrodynamics codes. While this has aided in our understanding of
  flare dynamics, it does not adequately represent the complexity of the
  interaction between thermal and non-thermal particles in a flaring
  region and cannot completely describe multi-wavelength observations
  of solar flares. In order to improve the current state-of-the-art
  flare simulations, we are combining thermal and stochastic non-thermal
  numerical modeling codes in order to simulate flare emission under a
  variety of theoretical and realistic solar conditions. The theoretical
  flare emission is then folded through the response functions of solar
  observatories in order to provide theoretical data that can be compared
  to observational results. This provides a means to test multiple flare
  models with observed flare behavior. This work was supported by NASA
  grant NAG5-12820

Title: CME Population Distributions: Science Facilitated by the VSO
Authors: Davey, A.; Wills-Davey, M.; Gurman, J.; Bogart, R.;
   Dimitoglou, G.; Hill, F.; Hourcle, J.; Martens, P.; Suarez Sola, I.;
   Tian, K.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSP23A..09D
Altcode:
  The Virtual Solar Observatory (VSO) exists to simplify and unify
  access to Solar Physics data. It provides a single interface to
  a broad spectrum of data types and sources which previously would
  have required considerable effort to collect. Using this ability to
  combine data sources, we access the entire SOHO/LASCO CME catalog and
  compare it with GOES observations of X-ray flares. Because we consider
  these data in their entirety, we find several instances where the
  results of less extensive studies may show unintentional selection
  effects. As a subpopulation, we specifically consider LASCO-observed
  halo CMEs. In agreement with previous studies, we find halo CMEs are
  the bulk of the fastest events. This selection effect is consistent
  with randomly-distributed CMEs extending over wide angles (&gt;120
  degrees). We also examine the lack of slower halo CMEs; otherwise
  randomly-distributed events are rarely Earth-directed. While geometric
  and Thomson scattering issues make less-energetic halo CMEs hard to
  detect, this dearth of slow observations may represent an additional
  seeing threshold. The lack of low-energy detections may account for the
  disparity in LASCO.s prediction of Kp ≥ 6 vs. Kp ≥ 5 geomagnetic
  storms.

Title: The Virtual Solar Observatory: Still a Small Box
Authors: Gurman, J. B.; Bogart, R. S.; Davey, A. R.; Dimitoglou, G.;
   Hill, F.; Hourclé, J. A.; Martens, P. C.; Suárez-Sola, I.; Tian,
   K. Q.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSH43B..03G
Altcode:
  Two and a half years after a design study began, and a year and a
  half after development commenced, version 1.0 of the Virtual Solar
  Observatory (VSO) was released at the 2004 Fall AGU meeting. Although
  internal elements of the VSO have changed, the basic design has
  remained the same, reflecting the team's belief in the importance of
  a simple, robust mechanism for registering data provider holdings,
  initiating queries at the appropriate provider sites, aggregating the
  responses, allowing the user to iterate before making a final selection,
  and enabling the delivery of data directly from the providers. In
  order to make the VSO transparent, lightweight, and portable, the
  developers employed XML for the registry, SOAP for communication
  between a VSO instance and data services, and HTML for the graphic
  user interface (GUI's). We discuss the internal data model, the API,
  and user responses to various trial GUI's as typical design issues for
  any virtual observatory. We also discuss the role of the "small box"
  of data search, identification, and delivery services provided by the
  VSO in the larger, Sun-Solar System Connection virtual observatory
  (VxO) scheme.

Title: Building a Virtual Solar Observatory: Lessons Learned
Authors: Bogart, R. S.; Tian, K. Q.; Davey, A.; Dimitoglou, G.;
   Gurman, J. B.; Hill, F.; Hourclé, J.; Martens, P. C.; Suárez-Sola,
   I.; Wampler, S.; Yoshimura, K.
Bibcode: 2005AGUSMSH51B..05B
Altcode:
  Two years into its development, the VSO has emerged from a drawing board
  concept into a full-fledged data query and data delivery system serving
  the Solar Physics community. Throughout its development, the VSO has
  lived up to its `small box' motto and has built light-weight servers
  that can easily run on a desktop or laptop. The two basic functions
  of the VSO are data query and data delivery. For these functions, the
  VSO servers act like switchboards, dispatching query/data requests
  to relevant data providers. More important, these servers present
  an abstraction that integrates diverse data archives, thus reducing
  complexity. The design of the VSO has evolved during its implementation
  in response to difficulties and user feedback. We discuss the changes
  in areas such as the data model, user interface, and performance. These
  lessons should be of interest to people designing and building other
  virtual observatories. We also discuss challenges and opportunities
  we foresee as the VSO becomes a significant and enabling research tool.

Title: EUV Observations of Active Region Dynamics
Authors: Deluca, E. E.; Cirtain, J. W.; del Zanna, G.; Mason, H. E.;
   Martens, P. C.; Schmelz, J.; Golub, L.
Bibcode: 2005AGUSMSP33A..03D
Altcode:
  Data collected during SoHO JOP 146, in collaboration with TRACE, is
  used to investigate the physical characteristics of coronal active
  region loops as a function of time and position along and across
  loop structures. These data include TRACE images in all three EUV
  passbands, and simultaneous CDS spectroscopic observations. Preliminary
  measurements of the loop temperature both along the loop half-length
  and loop cross-section are presented as a function of time. We will
  show the temperature and density profiles of several structures as a
  function of position, show changes in temperature and density with time
  and characterize the coronal background emission. Questions raised
  by these results will be greatly advanced with the high resolution
  spectra available from the EIS on Solar-B.

Title: An Hour in the Life of Coronal Loops
Authors: Cirtain, J. W.; Scott, J. T.; Martens, P. C. H.; Winter, H. D.
Bibcode: 2004AAS...205.1011C
Altcode: 2004BAAS...36R1351C
  Application of a new physics-based background subtraction method has
  allowed for investigation of the physical properties of coronal loops
  with unprecedented accuracy. We determine the temperature, emission
  measure, and pressure along multiple EUV coronal loops as a function of
  time and space, as well as their cross-section. With these measures of
  physical observables we have calculated the rate of change of pressure
  for the loops.

Title: Doing Science with the VSO: Signatures of CME Initiation
Authors: Davey, A. R.; Wills-Davey, M.; Gurman, J. B.; Bogart, R.;
   Tian, K. Q.; Martens, P.; Yoshimura, K.; Hill, F.; Suarez-Sola, I.;
   Hourclé, J.; Dimitoglou, G.; Wampler, S.
Bibcode: 2004AGUFMSH21B0414D
Altcode:
  The Virtual Solar Observatory (VSO) was designed to simplify and unify
  access to solar physics data. It provides a single interface to a broad
  range of data types and sources which previously would have required
  considerable effort to collect one by one. By combining access to online
  data sources with published scientific catalogs, the VSO can facilitate
  new science. This study seeks to investigate whether signatures of
  coronal mass ejection (CME) initiation can be used to constrain CME
  initiation models. We selected events from the SOHO/LASCO CME catalog,
  generated a time window between the calculated CME ``start time" and
  the first observation of the CME in LASCO C2, and examined EIT ``CME
  Watch" and H-alpha observations identified by a VSO query as falling in
  the specified time windows. We prioritized the EUV data by selecting
  those events for which GOES data indicated a flare, and identified
  flare sites and dimming regions in the EUV data, with the aim of more
  precisely determining CME initiation locations and times. In addition,
  we used H-alpha data to investigate CME's associated with by filament
  eruptions. The results allow us to calculate minimum acceleration rates,
  and determine correlations between coronal structures, ejection events,
  and acceleration rates. We use these correlations in turn to identify
  viable CME initiation mechanisms.

Title: Cosmological stabilization of moduli with steep potentials
Authors: Brustein, R.; de Alwis, S. P.; Martens, P.
Bibcode: 2004PhRvD..70l6012B
Altcode: 2004hep.th....8160B
  A scenario which overcomes the well-known cosmological overshoot
  problem associated with stabilizing moduli with steep potentials
  in string theory is proposed. Our proposal relies on the fact that
  moduli potentials are very steep and that generically their kinetic
  energy quickly becomes dominant. However, moduli kinetic energy
  redshifts faster than other sources when the universe expands. So,
  if any additional sources are present, even in very small amounts,
  they will inevitably become dominant. We show that in this case cosmic
  friction allows the dissipation of the large amount of moduli kinetic
  energy that is required for the field to be able to find an extremely
  shallow minimum. We present the idea using analytic methods and verify
  with some numerical examples.

Title: STEREO in the Virtual Solar Observatory Context
Authors: Hourcle, J. A.; Bogart, R.; Davey, A.; Gurman, J. B.; Hill,
   F.; Martens, P.; Suarez-Sola, I.; Tian, K.; Yoshimura, K.
Bibcode: 2004AGUFMSH21B0413H
Altcode:
  The Virtual Solar Observatory (VSO) was designed with the goal that it
  handle heterogeneous data sets from multiple observatories. With its
  two spacecraft and multiple instruments, the STEREO mission provides
  an excellent example of solar physics research based on multiple data
  sets, and a good test of the abilities of the VSO. Here we will discuss
  how the VSO will meet the key challenges that STEREO presents. In
  particular, the wide range of data classes and the non-stationary
  viewpoints of the two spacecraft demand a flexible underlying data
  model of the VSO.

Title: The Virtual Solar Observatory: status and initial operational
    experience
Authors: Hill, Frank; Bogart, Richard S.; Davey, Alisdair; Dimitoglou,
   George; Gurman, Joseph B.; Hourcle, Joseph A.; Martens, Petrus C.;
   Suarez-Sola, Igor; Tian, Karen; Wampler, Steven; Yoshimura, Keiji
Bibcode: 2004SPIE.5493..163H
Altcode:
  The Virtual Solar Observatory (VSO) is a bottom-up grassroots approach
  to the development of a distributed data system for use by the solar
  physics community. The beta testing version of the VSO was released in
  December 2003. Since then it has been tested by approximately 50 solar
  physicists. In this paper we will present the status of the project,
  a summary of the community's experience with the tool, and an overview
  of the lessons learned.

Title: On the Combination of TRACE and CDS data
Authors: Scott, J. T.; Cirtain, J. W.; Martens, P. C. H.; Winter, H. D.
Bibcode: 2004AAS...204.7307S
Altcode: 2004BAAS...36..801S
  Data collected by the Transition Region and Coronal Explorer (TRACE)
  and the Coronal Diagnostic Spectrometer (CDS) of an Active Region
  above the limb is examined. We have developed a co-alignment routine
  which finds the limb in each image and uses a cross correlation
  feature tracking algorithm to produce co-spatial images that are
  accurate to within 4\arcsec. TRACE generated an image for every CDS
  exposure. We have taken these images and selected only the portion of
  the TRACE field of view which was co-temporal with each CDS exposure,
  in essence generating a high resolution TRACE snapshot for each of the
  CDS exposures. We compare this image to the CDS raster, a composite of
  all 40 exposures taken during the study. We were able to determine the
  number of TRACE resolved features within each CDS pixel in an effort to
  provide an accurate lower bound estimate for the CDS filling factor. We
  were also able to show that structures with the same apparent brightness
  in the TRACE images are not necessarily at the same temperature and
  density. <P />This research is supported by NASA TRACE grant 426960,
  NASA GSRP fellowship 425175, and NASA grant NAG5-12820

Title: The Diffuse EUV Corona
Authors: Cirtain, J. W.; Martens, P. C. H.; Acton, L. W.; Scott, J. T.
Bibcode: 2004AAS...204.7304C
Altcode: 2004BAAS...36..800C
  Recent investigations have shown that the EUV corona could have two
  primary components; one at relatively static high temperature ( 2
  MK) and another dynamic at a low temperature (below 1 MK). These two
  coronal constituents are within the temperature ranges observed by
  the Transition Region and Coronal Explorer (TRACE), and are easily
  resolved using the spectral capabilities of the Coronal Diagnostic
  Spectrometer (CDS) on SoHO. We analyze an Active Region above the limb
  and determine emission measure scaling laws for the high temperature
  components. We also provide an estimate of the physical properties
  of the cool loops observed during the study. Through the use of the
  scaling laws we have developed a method to subtract the static coronal
  component from TRACE images. We then use the resultant TRACE 173 Å
  images to determine the changes in temperature and density in these
  loops as a function of time. This allows us to calculate the heating
  rate for the dynamic cool structures. <P />This work is supported in
  part via NASA GSRP fellowship (425175)

Title: Solar and Stellar X-ray Cycles
Authors: Martens, P. C. H.; SADE Team
Bibcode: 2004AAS...204.2103M
Altcode: 2004BAAS...36Q.688M
  Stern et al. have shown that Yohkoh-SXT full disk X-ray irradiance shows
  an 11 year cycle with an max/min amplitude ratio of a factor 30. Similar
  cyclic X-ray variation in Sun-like stars observed by ROSAT and its
  predecessors is observed in only a few cases and limited to a factor
  two or three. We will show, by means of detailed bandpass comparisons,
  that this discrepancy cannot be ascribed to the differences in energy
  response between SXT and the stellar soft X-ray detectors. Is the Sun
  exceptional? After centuries of geocentric and heliocentric worldviews
  we find this a difficult proposition to entertain. But perhaps the Sun
  is a member of a small class of late-type stars with large amplitudes
  in their X-ray cycles. The stellar X-ray observations listed in the
  HEASARC catalog are too sparse to verify this hypothesis. <P />To
  resolve these and related questions we have proposed a small low-cost
  stellar X-ray spectroscopic imager originally called SADE to obtain
  regular time series from late and early-type stars and accretion
  disks. This instrument is complimentary to the much more advanced
  Chandra and XMM-Newton observatories, and allows them to focus on those
  sources that require their full spatial and spectral resolution. We
  will describe the basic design and spectroscopic capability of SADE
  and show it meets the mission requirements.

Title: Implementation of the Virtual Solar Observatory
Authors: Davey, A. R.; Bogart, R. S.; Gurman, J. B.; Hill, F.; Hourcle,
   J.; Martens, P. C.; Suarez-Sola, I.; Tian, K. Q.; Yoshimura, K.
Bibcode: 2004AAS...204.7002D
Altcode: 2004BAAS...36..796D
  The Virtual Solar Observatory (VSO) integrates diverse solar data
  archives into a virtual collection providing common search and delivery
  services. Having developed from a prototype installation involving
  four major archives, it is now in the process of expanding to include
  a larger variety of archives and data types. We are also refining and
  expanding its services and user interfaces and defining an API. We
  have defined a working extensible data model enabling us to provide
  more detailed and comprehensive search capabilities and to incorporate
  additional data products. The API will allow people to construct their
  own interfaces to the core VSO functionality and integrate with other
  web services and other virtual observatories. Here we describe the
  structure of VSO as currently implemented and what is required to
  incorporate additional archives.

Title: The Virtual Solar Observatory -- the Why, What, How and Where
Authors: Hill, F.; Bogart, R. S.; Davey, A.; Dimitoglou, G.; Gurman,
   J. B.; Martens, P. C.; Tian, K.; Wampler, S.
Bibcode: 2003AGUFM.U22A0012H
Altcode:
  Observational solar physics almost always involves the comparison of
  several data sets obtained by different instruments and stored in a
  variety of archives. Currently a researcher must laboriously locate
  the relevant archives, search them with idiosyncratic interfaces,
  and retrieve the data by a number of methods. The VSO is a tool to
  streamline this process by providing a single unified interface and
  search tool for solar archives. Eventually this will be supplemented
  by distributed computing tools which will enable queries based on
  data itself, in addition to standard queries on metadata. The VSO
  will enable a new class of solar research -- large-scale correlative
  statistical studies on many data sets, thereby facilitating space
  weather studies. An example of a use case is a helioseismic study of the
  subsurface structure of cornal hole boundaries and possible predictive
  links between the solar interior and the solar wind. An intital
  prototype has been built linking archives at GSFC, Stanford, MSU, and
  NSO. This prototype has been constructed using a combination of XML,
  SOAP, and Perl technologies, and a beta release is available now. The
  initial set of archives will soon be expanded to include archives at
  HAO, NGDC, and selected NOAA feature and event catalogues. In the
  next 2 years, additonal service providers will be added, the user
  interface will be fully developed, and distributed computing tools
  will be initiated.

Title: The Effect of Background Subtraction on the Temperature of
    EIT Coronal Loops
Authors: Schmelz, J. T.; Beene, J. E.; Nasraoui, K.; Blevins, H. T.;
   Martens, P. C. H.; Cirtain, J. W.
Bibcode: 2003ApJ...599..604S
Altcode:
  We have selected a sample of 10 coronal loops that were clearly
  visible in the 171 Å passband of the SOHO EIT, five on the limb
  and five on the disk. Our analysis was limited to 171/195/284 image
  ``triplets''-observations taken when the instrument cycles through
  the different passbands during routine operations. This cycle takes
  only a few minutes, so each of these nonflaring structures did not
  change significantly during the cycle. We chose five pixels along
  each loop and five carefully selected background pixels. Temperature
  analysis was done four different ways: (1) standard EIT analysis on
  the five loop pixels with no background subtraction; (2) constant
  background subtraction for each EIT image; (3) pixel pair background
  subtraction; and (4) radial background array subtraction (this method
  works only for loops observed above the limb). Each method produced
  two estimates of temperature for each loop pixel, one from the 171:195
  ratio and the second for the 195:284 ratio. Both ratios produced loops
  with a uniform temperature, but each ratio results in a statistically
  different temperature value, perhaps indicating that the plasma along
  the line of sight was not isothermal. Background subtraction did
  not affect the EIT temperature analysis, i.e., the results were the
  same with and without background subtraction. The results for loops
  on the limb were ``cleaner'' i.e., had less scatter, than for loops
  on the disk. Finally, we did a similar temperature analysis with five
  randomly chosen pixels for each data set. The results were the same as
  for the loop pixels: two statistically different, uniform temperature
  ``structures.'' These findings indicate that EIT ratio analysis does
  not generate a physically meaningful value for the electron temperature.

Title: Measurements of Flux Cancellation During Filament Formation
Authors: Wood, Paul; Martens, Piet
Bibcode: 2003SoPh..218..123W
Altcode:
  We study the process of flux cancellation and filament formation in
  a nest of three decaying active regions, using data from SOHO MDI
  and EIT, and Hα images from Meudon and Big Bear. We find that there
  are no apparent EUV loops connecting the two poles of a cancelling
  feature prior to and during cancellation, suggesting an absence of
  coronal magnetic connectivity between these opposite polarity flux
  patches. We further find that the cancellation occurs at the ends of
  the Hα sections of the filament and is accompanied by a noticeable
  increase in Hα intensity and linkage of the Hα sections, but that the
  locations of the links remain the weakest in Hα absorption. We present
  our measurements of the amount of flux cancelled at each site and show
  it is in agreement with an estimate of the axial flux contained in
  the filament. We also observe two events of flux emergence, and find
  that they do not influence the filament formation in this case. We
  compare our results with similar measurements in recent papers and
  find agreement for the amounts of cancelled flux per patch, except
  for one case in a young emerging active region, for which we provide
  an alternative interpretation. We conclude that our measurements of
  flux cancellation are consistent with both the scenarios in which the
  filament is formed through ``head-to-tail" linkage, as well as the
  scenario in which filament flux tubes emerge as a whole from below
  the photosphere, but that only the former scenario is consistent with
  the apparent absence of coronal magnetic links between the cancelling
  magnetic patches.

Title: Data Integration in the Virtual Solar Observatory
Authors: Bogart, R. S.; Davey, A.; Dimitoglou, G.; Gurman, J. B.;
   Hill, F.; Martens, P. C.; Tian, K. Q.; Wampler, S.
Bibcode: 2003AGUFMSH42A0503B
Altcode:
  The aim of the Virtual Solar Observatory (VSO) is the integration of
  diverse data archives relevant to the study of Solar Physics into a
  virtual collection providing common search and delivery services. The
  back-end query services are implemented as Web Services and accessible
  via the Simple Object Access Protocol (SOAP). SOAP defines a remote
  procedure call mechanism that employs HTTP as its transport and
  encodes the client-server interactions in XML documents. In addition
  to its core function in identifying relevant datasets locally, a SOAP
  server at each data provider acts as a wrapper that maps descriptions
  in an abstract data model to those in the provider's specific model,
  and vice versa. Heterogeneous data search services can thereby be
  integrated with a common interface. This allows scientists to access
  multiple archives with differing data organizations at once, enhancing
  their ability to discover and and analyze correlative data from multiple
  sources. We have chosen two SOAP implementations for the VSO: SOAP::Lite
  and OpenSOAP. The former, written in Perl, is suitable for fast and
  flexible prototyping in data search applications. SOAP::Lite servers
  have been set up at each of the VSO archives, and can be readily
  installed at other servers. OpenSOAP, written in C with built-in
  support for service description and dispatch, may prove useful in
  transforming current computing utilities into Web Services. We report
  on initial experiments using OpenSOAP to provide additional services
  to the basic query functionality of VSO.

Title: SADE: The starspot and dynamo explorer
Authors: Martens, P. C. H.; Acton, L. W. A.; Klumpar, D.; Kankelborg,
   C.; Stern, R. A.; Peres, G.; Culhane, J. L.
Bibcode: 2003AdSpR..32.1123M
Altcode:
  We propose a mission called SADE, the Starspot And Dynamo Explorer, to
  study dynamo activity in nearby late-type stars. The onboard instruments
  will be a Ca-K telescope for magnetically dominated chromospheric
  emission, and an X-ray grazing incidence telescope to study coronal
  emission. We design the mission for a life-time of 15 years or longer
  to capture a full activity cycle for most solar-type stars. We aim to
  firmly establish the spectrum of the relation between chromospheric
  and corona' emission in late-type stars, and capture one or more stars
  going into or coming out of a Maunder type minimum. Operation costs will
  be kept to a minimum by automating mission operations to a maximum,
  and have the science operations be carried out by students at Montana
  State University.

Title: Analysis of a coronal loop on the limb
Authors: Cirtain, J. W.; Martens, P. C. H.; Winter, H. D.
Bibcode: 2003AdSpR..32.1117C
Altcode:
  The ability to accurately measure the temperature and density of the
  solar atmosphere is essential to understanding the physical nature of
  Coronal loops. After data has been corrected to account for cosmic ray
  incidents on the CCD and instrumental effects, there are additional
  sources of error that must also be addressed. We applied a correction
  to the intensities for spectral lines to account for line of sight
  effects. Having performed these procedures, the corrected intensities
  from the Coronal Diagnostic Spectrometer are then used to produce
  differential emission measure curves with much improved error estimates

Title: Yohkoh-SXT Observations of reconnection
Authors: Martens, P. C. H.
Bibcode: 2003AdSpR..32..905M
Altcode:
  In this paper I review the different strong indications for the
  occurrence of reconnection in the solar corona observed of with
  Yohkoh-SXT. I make a distinction between the unique indicator of
  reconnection, i.e. the change in connectivity in the magnetic field,
  and non-unique signatures of reconnection, that also can originate
  from other processes. I review five different types of Yohkoh-SXT
  observations that indicate reconnection in the solar corona: erupting
  plasmoids, X-ray jets, formation of sigmoids through "linkage", the
  existence of interconnecting loops, and the rigid rotation of coronal
  holes. I conclude that the presence of reconnection in the solar corona
  has been established with near certainty, but that higher resolution
  soft X-ray and EUV observations are needed to firmly establish the
  full physical picture for each of The phenomena described.

Title: The Role of Magnetic Reconnection in the Formation of
    Transequatorial Loops
Authors: Martens, P. C. H.
Bibcode: 2003SPD....34.1002M
Altcode: 2003BAAS...35..825M
  Transequatorial loops often bridge large regions of very small field
  strength in which no emergence other than that of tiny dipoles is
  observed. It is very unlikely on theoretical grounds, and has never
  been observed, that such loops emerge as pre-existing flux tubes from
  below the chromosphere. Moreover, of the two active regions that these
  loops connect one is usually demonstrably older than the other, so
  that a loop connecting them could not have emerged with the older one,
  because it would have had nowhere to connect to. Taken together this
  is nearly indisputable evidence of reconnection in the corona. <P />I
  will review a number of recently published observations that support
  the statements above, and consider the implications for dynamo models
  from the coronal formation of transequatorial loops

Title: The Virtual Solar Observatory: The Best-Laid Schema
Authors: Gurman, J. B.; Dimitoglou, G.; Hill, F.; Wampler, S.; Bogart,
   R. S.; Tian, K.; Martens, P.; Davey, A.
Bibcode: 2003SPD....34.0203G
Altcode: 2003BAAS...35..807G
  Work on a protoype Virtual Solar Observatory (VSO) is now under way. The
  prototype will offer access to data from online solar archives at
  Stanford, NSO, Montana State, and the SDAC. We discuss some of the
  features of the VSO for users, as well as the basic design and some
  of the technical aspects, including the use of XML schemas and SOAP
  to allow users a single access method for disparate data services.

Title: TRACE and CDS: JOP 146 Data Analysis Part I
Authors: Scott, J. T.; Cirtain, J. W.; Martens, P. C. H.
Bibcode: 2003SPD....34.1705S
Altcode: 2003BAAS...35..838S
  Joint Observing Program 146 was designed to collect data on coronal
  loops using the Coronal Diagnostic Spectrometer on SoHO and the
  Transition Region and Coronal Explorer. These two instruments
  collectively provide high spatial, temporal and temperature
  resolution. Calibration of the 171 Å filter on TRACE to spectral
  line intensities collected by CDS combines these qualities to produce
  the most detailed data currently available for the solar corona. We
  have determined an absolute value for the wavelengths of ions in
  data collected on September 18, 2001. This wavelength was then used
  to determine the Doppler shifts for many points along a coronal
  loop. The resulting values for velocity and intensity of Mg IX were
  then compared to the flux measured by the TRACE 171 Å filter. We find
  a appreciable correlation between the 171 Å filter and Mg IX. We use
  this determination to develop method of Differential Emission Measure
  analysis that provides a DEM for any pixel along a loop at nearly the
  same instant in time. This is uncharacteristic of DEM curves typically
  created from CDS data, as these curves are highly time dependant.

Title: First Steps Towards a VSO
Authors: Davey, A. R.; Bogart, R. S.; Dimitoglou, G.; Gurman, J. B.;
   Hill, F.; Martens, P. C.; Tian, K. Q.; Wampler, S.
Bibcode: 2003SPD....34.0311D
Altcode: 2003BAAS...35..810D
  Work has started on constructing the Virtual Solar Observatory. This
  poster describes some of the components of the VSO and the first steps
  that have been taken to implement these components. A description of
  the overall VSO structure is given, along with descriptions of data
  and meta-data models, methods by which these data model are used by
  the VSO, details of how VSO nodes are interconnected <SUP>*</SUP>
  and ideas on the likely format of the VSO API. As an example, the
  inclusion of Yohkoh-SXT data at MSU and the future inclusion of the
  Yohkoh-Galileo project data will be discussed. <P /><SUP>*</SUP>
  See also ``Data Integration Using SOAP in the VSO" by Tian et al.

Title: SADE: Starspot and Dynamo Explorer
Authors: Martens, P. C. H.
Bibcode: 2003SPD....34.2003M
Altcode: 2003BAAS...35..844M
  In soft X-rays the solar coronal radiance varies by a factor of 70
  over the solar activity cycle. A similar variation in most stars
  in the existing X-ray database has not been found (Stern 2001);
  even stars which exhibit chromospheric activity cycles show only
  marginal evidence for X-ray cycles. This is rather puzzling as the
  time span and multiple coverage of the X-ray sky should reveal at
  least a hint of such a pronounced cyclical variation. <P />By the time
  of the meeting we will have submitted a SMEX proposal with the above
  acronym to determine the nature and amplitude of the variation in X-ray
  emission of nearby solar analogs that have a cyclic chromospheric Ca-K
  variability similar to that of the Sun. In doing so we aim to expand
  our knowledge of the parameter space of stellar dynamos, which will
  lead to a better understanding of the dynamo process in general --
  an unresolved fundamental problem in astrophysics -- and the solar
  dynamo in particular. This is an investigation at the cross-section
  of the NASA themes ``Structure and Evolution of the Universe", and
  the ``Sun-Earth Connection". <P />In my presentation I will describe
  the SADE instrument design, observing strategy, and possible science
  results. SADE is proposed by a consortium led by MSU, including Swales,
  CfA, LMSAL, UCL, OAP, and Bangalore.

Title: Building an On-line Catalog of Correlated Solar Prominence
    and Sigmoid Images
Authors: Merriot, I. V.; Pevtsov, A.; Martens, P.
Bibcode: 2003SPD....34.0310M
Altcode: 2003BAAS...35R.809M
  Predicting solar weather is a complex endeavor. The correlation between
  X-ray sigmoids and coronal mass ejections (CMEs) has been established
  but the role of the prominence in association with the sigmoid and
  CME is not yet clear. This study catalogs the correlation between
  prominence behavior and sigmoids --before and after-- a CME takes
  place. <P />CME, sigmoid and filament occurrences were correlated
  using the Yashiro online catalog (SOHO), the SXT sigmoid catalog
  (Yohkoh) and archived H-alpha film from the flare patrol telscope
  (NSO/SP). When correlations were found, the H-alpha full disk images
  were digitized to embrace time periods of 2-3 hours before and after
  the CME event where changes in filament were notable. The culmination
  of this study will be a web-based catalog of data in text and images
  showing filament dynamics when sigmoids leading to CMEs are present. <P
  />This study is funded, in part, by the Murdoch Foundation.

Title: Data Integration Using SOAP in the VSO
Authors: Tian, K. Q.; Bogart, R. S.; Davey, A.; Dimitoglou, G.;
   Gurman, J. B.; Hill, F.; Martens, P. C.; Wampler, S.
Bibcode: 2003SPD....34.0312T
Altcode: 2003BAAS...35..810T
  The Virtual Solar Observatory (VSO) project has implemented a time
  interval search for all four participating data archives. The back-end
  query services are implemented as web services, and are accessible
  via SOAP. SOAP (Simple Object Access Protocol) defines an RPC (Remote
  Procedure Call) mechanism that employs HTTP as its transport and encodes
  the client-server interactions (request and response messages) in XML
  (eXtensible Markup Language) documents. <P />In addition to its core
  function of identifying relevant datasets in the local archive, the SOAP
  server at each data provider acts as a "wrapper" that maps descriptions
  in an abstract data model to those in the provider-specific data model,
  and vice versa. It is in this way that VSO integrates heterogeneous
  data services and allows access to them using a common interface. Our
  experience with SOAP has been fruitful. It has proven to be a better
  alternative to traditional web access methods, namely POST and GET,
  because of its flexibility and interoperability.

Title: Strawman Concept for A Virtual Solar Observatory
Authors: Martens, P. C. H.; Gurman, J. B.; Hill, F.; Bogart, R. S.;
   Davey, A.; Dimitoglou, G.; Tian, K.; Wampler, S.
Bibcode: 2002AAS...20114103M
Altcode: 2003BAAS...35..567M
  We propose here an architecture and feature set for a prototype Virtual
  Solar Observatory (VSO). The prototype will not include all the features
  that might eventually become part of the VSO, nor even all the features
  that are concurrently under development elsewhere that should become
  parts of the VSO's functionality. It is possible to approach the design
  of such a system in at least two different ways. In one (top-down),
  all possible features and uses of a system are studied, and the best
  solution for as many as possible is proposed. This is the approach
  taken by the European Grid of Solar Observations (EGSO). Alternately,
  one can approach a system design from the bottom up, and ask what the
  essential element or elements of the design have to be in order to have
  a functioning and useful system. <P />The VSO study group decided, after
  examining different approaches to abstracting the procedures for solar
  data identification and access, to build the “smallest box” possible
  around that problem, rather than attempting to draw a box around all
  possible aspects of a VSO. This design will be presented in the poster.

Title: The Right Amount of Glue: Technologies and Standards Relevant
    to a Future Solar-Terrestrial Data Environment
Authors: Gurman, J. B.; Dimitoglou, G.; Bogart, R. S.; Tian, K. Q.;
   Hill, F.; Wampler, S.; Martens, P. C.; Davey, A.
Bibcode: 2002AGUFMSH52C..03G
Altcode:
  In order to meet the challenge of developing a new system science, we
  will need to employ technology that enables researchers to access data
  from fields with which they are at least initially unfamiliar as well as
  from sources they use more regularly. At the same time, the quantity of
  data to be obtained by missions such as the Solar Dynamics Observatory
  demands ease and simplicity of data access. These competing demands
  must in turn fit within severely constrained funding for data analysis
  in such projects. \p Based on experience in only a single discipline
  but with a diversity of data types and sources, we will give examples
  of technology that have made a significant difference in the way people
  do science. Similarly, we will show how adoption of a well-dcoumented
  data format has made it easier for one community to search, reduce,
  and analyze data. We will also describe a community-supported data
  reduction and analysis software tree with useful features.\p We will
  attempt to generalize the lessons learned in these instances to features
  the broader, solar-terrestrial community might find compelling, while
  avoiding overdesign of a common data environment.\p

Title: The Inadequacy of Temperature Measurements in the Solar Corona
    through Narrowband Filter and Line Ratios
Authors: Martens, P. C. H.; Cirtain, J. W.; Schmelz, J. T.
Bibcode: 2002ApJ...577L.115M
Altcode:
  We analyze the determination of coronal line-of-sight temperatures
  with the technique of narrowband filter ratios that is currently
  employed for data obtained with the Transition Region and Coronal
  Explorer and the EUV Imaging Telescope on board the Solar and
  Heliospheric Observatory. We demonstrate that the simple fact that
  the observed differential emission measure curves in coronal loops
  have a broad plateau everywhere along the length of the loop leads to
  the finding of isothermal loops with different temperatures for each
  pair of filters. We show that none of the temperatures thus obtained
  correctly describe the state of the loop plasma, which instead must be
  characterized by the full differential emission measure per pixel. We
  conclude that the recent discovery of a new class of isothermal loops
  is probably a mere artifact of the narrowband filter ratio method and
  show that the shift in the location of the plateau in the differential
  emission measure along the loop indicates significant heating near
  the loop tops.

Title: Methods of Temperature and Emission Measure Determination of
    Coronal Loops
Authors: Cirtain, J. W.; Schmelz, J. T.; Martens, P. C. H.
Bibcode: 2002AAS...200.1605C
Altcode: 2002BAAS...34..667C
  Recent observational results from both SOHO-EIT and TRACE indicate that
  coronal loops are isothermal along their length (axially). These results
  are obtained from a narrowband filter ratio method that assumes that
  the plasma is isothermal along the line of sight (radially). However,
  these temperatures vary greatly from those derived from differential
  emission measure (DEM) curves produced from spectral lines recorded by
  SOHO-CDS. The DEM results indicate that the loops are neither axially
  nor radially isothermal. This discrepancy was investigated by Schmelz
  et al. (2001). They chose pairs of iron lines from the same CDS data
  set to mimic the EIT and TRACE loop results. Ratios of different
  lines gave different temperatures, indicating that the plasma was not
  radially isothermal. In addition the results indicated that the loop
  was axially isothermal, even though the DEM analysis of the same data
  showed this result to be false. Here we have analyzed the EIT data for
  the CDS loop published by Schmelz et al. (2001). We took the ratios of
  the 171-to-195 and 195-to-284 filter data, and made temperature maps
  of the loop. The results indicate that the loop is axially isothermal,
  but different temperatures were found for each pair of filters. Both
  ratio techniques force the resultant temperature to lie within the range
  where the response functions (for filters) or the emissivity functions
  (for lines) overlap; isothermal loops are therefore a byproduct of
  the analysis. This conclusion strengthens support for the idea that
  temperature and emission measure results from filter ratio methods may
  be misleading or even drastically wrong. This research was funded in
  part by the NASA/TRACE MODA grant for Montana State University. Solar
  physics research at the University of Memphis is supported by NASA
  grant NAG5-9783.

Title: The Point Spread Function of the Yohkoh Soft X-ray Telescope
Authors: McKenzie, D. E.; Gburek, S.; Acton, L. W.; Martens, P. C.
Bibcode: 2002AAS...200.5502M
Altcode: 2002BAAS...34Q.732M
  The point spread function (PSF) of the Yohkoh solar observatory's Soft
  X-ray Telescope has two primary components, a sharply defined core
  and a diffuse wing due to photon scattering. Because the extent of the
  PSF is significantly wider than a single pixel, its characterization is
  useful for improvement of the quality of the SXT images. We will present
  results from analyses of the two PSF components, and demonstrate our
  best model of the core and scattering wing of the SXT point spread
  function. An example of PSF deconvolution to remove the effects of
  photon scattering will be given.

Title: How to `Subtract' Spectrally Determined Intensities from a
    Coronal Loop on the Limb
Authors: Martens, P. C. H.; Cirtain, J. W.; Schmelz, J. T.
Bibcode: 2002AAS...200.0206M
Altcode: 2002BAAS...34..640M
  There are two main problems in the determination of plasma emissions
  within a coronal loop. First, the line of sight adds the ambient
  background to the measurement. Second, scattering elevates the intensity
  for pixels close to a structure (i.e. a loop) by counting photons that
  actually are emitted from that structure. Here we have a possible
  solution for these two problems. We show that the intensities for
  the spectral lines are shown to have scale height dependence when the
  plasma is not confined to a structure. Accordingly, at any distance
  greater than its scale height, the ion will not have a statistically
  significant contribution to the measure of intensity. Additionally,
  an isolated coronal structure will have a maximum intensity value along
  an exposure and within a range of pixels that effectively slice a leg
  of the loop. The maximum is the location of the pixel that is most
  likely the one containing the loop. All other pixels are considered
  scatter until the point spread function can deconvolve the true value
  for intensity per pixel. The resulting values for intensity have then
  been reduced to approximate the value for intensity for the plasma
  within the loop. Now the intensity has been reduced to the intensity
  of the ion within the loop and the analysis of an accurate DEM is now
  possible. This research was funded in part by the NASA/TRACE MODA grant
  for Montana State University. Solar physics research at the University
  of Memphis is supported by NASA grant NAG5-9783.

Title: Building a Virtual Solar Observatory: I Look Around and
    There's a Petabyte Following Me
Authors: Gurman, J. B.; Bogart, R.; Hill, F.; Martens, P.
Bibcode: 2002AAS...200.5805G
Altcode: 2002BAAS...34..740G
  The 2001 July NASA Senior Review of Sun-Earth Connections missions
  and data centers directed the Solar Data Analysis Center (SDAC) to
  proceed in studying and implementing a Virtual Solar Observatory (VSO)
  to ease the identification of and access to distributed archives of
  solar data. Any such design (cf. the National Virtual Observatory
  and NASA's Planetary Data System) consists of three elements: the
  distributed archives, a "broker" facility that translates metadata
  from all partner archives into a single standard for searches,
  and a user interface to allow searching, browsing, and download of
  data. Three groups are now engaged in a six-month study that will
  produce a candidate design and implementation roadmap for the VSO. We
  hope to proceed with the construction of a prototype VSO in US fiscal
  year 2003, with fuller deployment dependent on community reaction to
  and use of the capability. We therefore invite as broad as possible
  public comment and involvement, and invite interested parties to a
  `birds of a feather' session at this meeting. VSO is partnered with
  the European Grid of Solar Observations (EGSO), and if successful, we
  hope to be able to offer the VSO as the basis for the solar component
  of a Living With a Star data system.

Title: Differential Emission Measure Error Analysis
Authors: Winter, H. D.; Martens, P. C. H.
Bibcode: 2002AAS...200.0205W
Altcode: 2002BAAS...34..640W
  While line ratio techniques are still the dominant method for making
  measurements of solar coronal plasma parameters, such as mean electron
  density and electron temperature, the isothermal approximation
  on which these methods rely is a poor assumption for many solar
  features. Differential emission measure (DEM) analysis eliminates
  the isothermal assumption. The inverse problem that one must solve to
  generate DEM curves is ill-posed, yielding multiple solutions that fit
  the observed data. Forward modeling improves the situation but still
  does not allow one to derive a unique solution that properly models
  the observed plasma. For DEM curves to have scientific meaning an
  estimate of the error must be included. We generated DEM curves for
  several observed solar coronal features and determined the error in
  each solution from photon statistics. This allows us to use statistical
  methods to derive the best DEM fit to the data with the smallest number
  of free parameters. The possible implications for the physics derived
  from DEM analysis are significant. This work was supported by the MSU
  NASA/TRACE MO&amp;DA contract.

Title: SADE, the Student Astrophysical Dynamo Explorer
Authors: Martens, P.; Acton, L.; Klumpar, D.; Stern, R.; Peres, G.;
   Culhane, L.
Bibcode: 2002cosp...34E1298M
Altcode: 2002cosp.meetE1298M
  In soft x-rays the solar coronal radiance varies by a factor of 10-30
  over the solar activity cycle. A similar variation in most stars in
  the existing x-ray database has not been found (Stern 2001); even
  stars which exhibit chromospheric activity cycles show only marginal
  evidence for X-ray cycles. This is rather puzzling as the time span
  and multiple coverage of the x-ray sky should reveal at least a hint of
  such a pronounced cyclical variation. We propose a mission called the
  Student Astrophysical Dynamo Explorer to measure the x-ray brightness
  of about 75 stars once every 5 days for up to 15 years. Selection of
  prime stars takes into account location (avoid eclipse), rotation rate,
  Ca-K observations, and magnetic field strength, to focus on the best
  candidates for dynamo studies. We baseline a nested 4-5 mirror system
  with 200 cm^2 geometric area, with a 1.5 to 2 meter focal length, 15
  arcsec on-axis resolution, and Au or Ni coatings. The strawman detector
  is a back-illuminated CCD of 512x512 pixels, with pixels that can be
  large as a 15 arcseconds. Available exposure time per star per visit
  is about an hour and a half. We are exploring the option of adding
  a visible light detector for astroseismology. To minimize operations
  cost for this long duration mission we envisage tracking and commanding
  from a simple ground station at Montana State University, operated by
  students under the auspices of MSU's Space Science and Engineering Lab
  (SSEL).

Title: Preface
Authors: Martens, P. C. H.; Cauffman, D. P.
Bibcode: 2002mwoc.confD...5M
Altcode:
  No abstract at ADS

Title: The Origin of Prominences and Their Hemispheric Preference
    for the Skew of Overlying X-ray Loops
Authors: Martens, P. C. H.
Bibcode: 2002mwoc.conf..135M
Altcode:
  I present a ``head-to-tail'' inkage model for the formation, evolution,
  and eruption of solar filaments. The magnetic field structure of the
  model is based upon the observation that filaments form exclusively
  in filament channels with no apparent magnetic connections above
  the polarity inversion line. The formation of a filament in this
  configuration is driven by flux convergence and cancellation, which
  produces loop-like filaments segments with a half-turn. Filament
  segments of like chirality may connect and form long quiescent
  filaments. I demonstrate that the combined workings of Hale's polarity
  law, Joy's law, and differential rotation introduce a strong hemispheric
  preference in the chirality of filaments formed poleward of the sunspot
  belt, in agreement with observations. I analyze the magnetic fine
  structure of filaments formed through the model and find consistency
  with the observed hemispheric preference for the skew of overlying
  X-ray emitting loops observed by Yohkoh-SXT, contrary to what would
  be expected from differential rotation. Finally I show that every
  cancellation event that generates a filament obeying the hemispheric
  chirality preference, injects a flux tube below the surface with a
  poloidal field opposite to that of the ongoing cycle. I suggest that
  this pattern of submergence of flux represents the specific mechanism
  for the reversal of the poloidal flux in a Babcock-Leighton-Durney
  type model for the solar dynamo.

Title: Analysis of a coronal loop on the limb
Authors: Cirtain, J.; Martens, P.
Bibcode: 2002cosp...34E1294C
Altcode: 2002cosp.meetE1294C
  The determination of line of sight temperature and density for
  coronal loops has been an elusive process. The need for the ability
  to accurately measure these plasma characteristics is key to the
  understanding of their physical nature. Accordingly, we have been
  testing procedures to determine our best approach to this problem. We
  have concluded that spectroscopically determined Differential Emission
  Measures, DEMs, provide the most precise measure available with current
  instrumentation. Of course there is the problem of the addition of
  values for intensities from ions emitting outside the structure,
  yet along the line of sight. We have also been able to show that ion
  production in the quite corona follows predictions of density scaling
  laws and accordingly, values for the intensity at distance greater than
  the scale height are structure dependant and any line of sight effects
  become negligible. Furthermore, through the use of narrow filter images
  taken by TRACE, the time component of the DEM can be constrained in a
  way that allows for comparison of emission from the filter to emission
  from ions that are formed at approximately the same temperature. This
  allows us to produce DEM curves for all points along a loop at each time
  an image from TRACE exists. This allows us to track the evolution of a
  loop through its lifetime in both temperature and density. Accordingly,
  if the injection of energy into a loop is discrete in within the loop,
  the DEM curves will provide evidence of this process.

Title: Blind Deconvolution of the SXT PSF Core Part
Authors: Gburek, S.; Sylwester, J.; Martens, P. C. H.
Bibcode: 2002mwoc.conf..417G
Altcode:
  The performance and speed of blind deconvolution algorithms for
  restoration of SXT images depend on good initial guess for PSF function
  shape. From the analysis of several compact flare kernels we came
  to conclusion that a good guess for PSF can be provided directly
  from images of X-ray compact structures observed by SXT. Recently,
  we conducted extensive mission-long searches for compact structures
  through entire database of SXT full resolution frames. The searches
  returned plenty compact structures which my serve to construct
  initial approximation of the PSF for BID restoration method. We show a
  selection of the most compact structures found and its location on SXT
  CCD detector. Using observation for this selected set of structures
  we construct constraints for Al12 PSF shrouds and compare them with
  ground calibration data.

Title: Multi-Wavelength Observations of Coronal Structure and Dynamics
Authors: Martens, P. C. H.; Cauffman, D.
Bibcode: 2002mwoc.conf.....M
Altcode:
  Yohkoh, a mission of Japan's Institute of Space and Astronautical
  Sciences with the cooperation of the United States and United Kingdom
  was launched a decade ago on 30 August 1991. This scientific meeting
  has been organized in celebration of ten years of successful scientific
  operation of Yohkoh. We will review the many and varied advances in our
  understanding of the dynamic solar atmosphere in the past 10 years of
  observations by Yohkoh in collaboration with SoHO, TRACE, Ulysses, and,
  soon, HESSI. The meeting will focus on the conceptual and theoretical
  advances that coordinated multi- mission and ground based observations
  of the Sun have enabled in the last decade, and examine the role that
  continued observations by Yohkoh will play within the context of the
  programs of the current decade, such as HESSI, Solar-B, STEREO, and
  the Solar Dynamics Observatory.

Title: Science objectives of the EUV spectral imager for Solar Orbiter
Authors: Martens, Petrus C.; Kankelborg, Charles C.
Bibcode: 2001ESASP.493..293M
Altcode: 2001sefs.work..293M
  No abstract at ADS

Title: Simultaneous EUV imaging and spectroscopy
Authors: Kankelborg, Charles C.; Martens, Petrus C.; Thomas, Roger J.
Bibcode: 2001ESASP.493..257K
Altcode: 2001sefs.work..257K
  No abstract at ADS

Title: Chromospheric Damping of Alfvén Waves
Authors: De Pontieu, B.; Martens, P. C. H.; Hudson, H. S.
Bibcode: 2001ApJ...558..859D
Altcode:
  We analytically study the damping of Alfvén mode oscillations in the
  chromosphere and in coronal loops. In the partially ionized chromosphere
  the dominant damping process of Alfvén waves is due to collisions
  between ions and neutrals. We calculate the damping time for Alfvén
  waves of a given frequency, propagating through model chromospheres
  of various solar structures such as active region plage, quiet sun,
  and the penumbra and umbra of sunspots. For a given wave frequency,
  the maximum damping always occurs at temperature minimum heights and
  in the coldest structure(s), i.e., the umbra of sunspots. Energy
  dissipation due to ion-neutral damping of Alfvén waves with an
  energy flux of 10<SUP>7</SUP> ergs cm<SUP>-3</SUP> s<SUP>- 1</SUP> can
  play a considerable role in the energy balance of umbrae, quiet sun,
  and plage for Alfvén wave periods of the order, respectively, 50,
  5, and 0.5 s. We also consider Alfvén waves in coronal loops and the
  leakage of wave energy through the footpoints. We assume a three-layer
  model of coronal loops with constant Alfvén speed v<SUB>A</SUB>
  (and no damping) in the corona, v<SUB>A</SUB> varying exponentially
  with height in the dissipative chromosphere, and v<SUB>A</SUB> again
  constant in the photosphere at the end of the loop. We find an exact
  analytical solution in the chromospheric part. Using these solutions, we
  estimate the leakage of wave energy from the coronal volume through the
  footpoint regions of the loop and find that the presence of a moderate
  amount of chromospheric damping can enhance the footpoint leakage. We
  apply this result to determine the damping time of standing waves in
  coronal loops. The enhanced footpoint leakage also has implications
  for theories of coronal heating based on resonant absorption. Finally,
  we find exact expressions for the damping of Alfvén waves launched
  in the photosphere and upward propagating through the chromosphere
  and into the corona. The partially ionized chromosphere presents an
  effective barrier for upward propagating Alfvén waves with periods
  less than a few seconds.

Title: Origin and Evolution of Filament-Prominence Systems
Authors: Martens, Petrus C.; Zwaan, Cornelis
Bibcode: 2001ApJ...558..872M
Altcode:
  We present a ``head-to-tail'' linkage model for the formation,
  evolution, and eruption of solar filaments. The magnetic field
  structure of our model is based on the observation that filaments
  form exclusively in filament channels with no apparent magnetic
  connections above the polarity inversion line. The formation of
  a filament in this configuration is driven by flux convergence
  and cancellation, which produces looplike filament segments with
  a half-turn. Filament segments of like chirality may connect and
  form long quiescent filaments. Such filaments are stabilized through
  footpoint anchoring until further cancellation at the footpoints causes
  their eruption. The eruption restores the original filament channel so
  that filament formation may resume immediately. We then demonstrate
  that the combined workings of Hale's polarity law, Joy's law, and
  differential rotation introduce a strong hemispheric preference
  in the chirality of filaments formed poleward of the sunspot belt,
  which is in agreement with observations. We analyze the magnetic fine
  structure of filaments formed through our model and find consistency
  with the observed hemispheric preference for barb orientation and
  a simple explanation for barb formation. Finally, we consider the
  flux tubes retracted below the surface in the process of filament
  formation. We show that every cancellation event that generates a
  filament obeying the hemispheric chirality preference injects a flux
  tube below the surface with a poloidal field opposite that of the
  ongoing cycle. We suggest that this pattern of submergence of flux
  represents the specific mechanism for the reversal of the poloidal
  flux in a Babcock-Leighton-Durney-type model for the solar dynamo.

Title: The Origin of Prominences and Their Hemispheric Preferences
Authors: Martens, P. C.
Bibcode: 2001AGUSM..SH42A01M
Altcode:
  We present a ``head-to-tail" linkage model for the formation,
  evolution, and eruption of solar filaments. The magnetic field
  structure of our model is based upon the observation that filaments
  form exclusively in filament channels with no apparent magnetic
  connections above the polarity inversion line. The formation of a
  filament in this configuration is driven by flux convergence and
  cancellation, which produces loop-like filaments segments with a
  half-turn. Filament segments of like chirality may connect and form long
  quiescent filaments. Such filaments are stabilized through footpoint
  anchoring until further cancellation at the footpoints causes their
  eruption. The eruption restores the original filament channel so that
  filament formation may resume immediately. We demonstrate that the
  combined workings of Hale's polarity law, Joy's law, and differential
  rotation introduce a strong hemispheric preference in the chirality
  of filaments formed poleward of the sunspot belt, in agreement with
  observations. We analyze the magnetic fine structure of filaments formed
  through our model and find consistency with the observed hemispheric
  preference for barb orientation and a simple explanation for barb
  formation. Finally we show that every cancellation event that generates
  a filament obeying the hemispheric chirality preference, injects a flux
  tube below the surface with a poloidal field opposite to that of the
  ongoing cycle. We suggest that this pattern of submergence of flux
  represents the specific mechanism for the reversal of the poloidal
  flux in a Babcock-Leighton-Durney type model for the solar dynamo.

Title: SOHO (Solar and Heliospheric Observatory)
Authors: Martens, P.
Bibcode: 2000eaa..bookE1978M
Altcode:
  The Solar and Heliospheric Observatory (SOHO) is a project of
  international cooperation between ESA (the EUROPEAN SPACE AGENCY)
  and NASA to study the Sun, from its deep core to the outer corona,
  and the solar wind. SOHO was launched on 2 December 1995, on top of
  an Atlas/Centaur combination, from Cape Canaveral Air-Force Base in
  Florida. It reached its operating orbit around the L1 Sun-Earth Lagr...

Title: Solar Flares: Preflare Phase
Authors: Martens, P.
Bibcode: 2000eaa..bookE2288M
Altcode:
  Solar flares are believed to be the result of a sudden conversion of
  a large amount of free magnetic energy, previously stored in the solar
  CORONA. The release takes place in a matter of minutes to half an hour,
  and the amount of energy involved can be up to 1026 J (1033 erg)....

Title: Solar Plumbing? Constraints on the 3D geometry of
    constant-width coronal loops.
Authors: Martens, P. C. H.; Kankelborg, C. C.
Bibcode: 2000SPD....31.0144M
Altcode: 2000BAAS...32R1289M
  Coronal loops are observed to have nearly constant apparent width
  (Klimchuk, 1999; Watko &amp; Klimchuk, 1999). We will show that only
  one basic geometry is possible for constant-width coronal loops in
  a force free magnetic field. In particular, the loop must describe a
  helix. Furthermore, the torsion of the loop is determined solely by
  the value of the force free parameter, alpha = (curl B) / B.

Title: On the Nature of the ``Moss'' Observed by TRACE
Authors: Martens, P. C. H.; Kankelborg, C. C.; Berger, T. E.
Bibcode: 2000ApJ...537..471M
Altcode:
  ``Moss'' is the name given to low-lying (~3000 km), hot (~1 MK) solar
  coronal plasma that has been observed recently by the Transition
  Region and Coronal Explorer (TRACE). This paper investigates two
  hypotheses regarding the nature of the moss: (1) emission from small,
  million degree loops; (2) emission from the legs of 3-10 million
  degree loops. We update the coronal radiative loss curve, using the
  most recent results for coronal abundances, and use an analytical loop
  model to find that the first hypothesis requires a filling factor close
  to unity to reproduce the observed emission measure, while the second
  hypothesis results in a filling factor of about 0.1, in agreement
  with other independent multiwavelength analyses of moss. We find that
  the vertical extent and the height of the moss layer above the limb
  are also very well reproduced with the second hypothesis. We further
  show that the observed brightness of the moss scales linearly with
  the loop pressure and filling factor, independent of the loop length,
  and we derive a general expression for the conversion factor.

Title: Time Variability of the ``Quiet'' Sun Observed with
    TRACE. II. Physical Parameters, Temperature Evolution, and Energetics
    of Extreme-Ultraviolet Nanoflares
Authors: Aschwanden, Markus J.; Tarbell, Ted D.; Nightingale, Richard
   W.; Schrijver, Carolus J.; Title, Alan; Kankelborg, Charles C.;
   Martens, Piet; Warren, Harry P.
Bibcode: 2000ApJ...535.1047A
Altcode:
  We present a detailed analysis of the geometric and physical
  parameters of 281 EUV nanoflares, simultaneously detected with the
  TRACE telescope in the 171 and 195 Å wavelengths. The detection and
  discrimination of these flarelike events is detailed in the first paper
  in this series. We determine the loop length l, loop width w, emission
  measure EM, the evolution of the electron density n<SUB>e</SUB>(t) and
  temperature T<SUB>e</SUB>(t), the flare decay time τ<SUB>decay</SUB>,
  and calculate the radiative loss time τ<SUB>loss</SUB>, the conductive
  loss time τ<SUB>cond</SUB>, and the thermal energy E<SUB>th</SUB>. The
  findings are as follows: (1) EUV nanoflares in the energy range of
  10<SUP>24</SUP>-10<SUP>26</SUP> ergs represent miniature versions
  of larger flares observed in soft X-rays (SXR) and hard X-rays
  (HXR), scaled to lower temperatures (T<SUB>e</SUB>&lt;~2 MK),
  lower densities (n<SUB>e</SUB>&lt;~10<SUP>9</SUP> cm<SUP>-3</SUP>),
  and somewhat smaller spatial scales (l~2-20 Mm). (2) The cooling
  time τ<SUB>decay</SUB> is compatible with the radiative cooling
  time τ<SUB>rad</SUB>, but the conductive cooling timescale
  τ<SUB>cond</SUB> is about an order of magnitude shorter, suggesting
  repetitive heating cycles in time intervals of a few minutes. (3)
  The frequency distribution of thermal energies of EUV nanoflares,
  N(E)~10<SUP>-46</SUP>(E/10<SUP>24</SUP>)<SUP>-1.8</SUP> (s<SUP>-1</SUP>
  cm<SUP>-2</SUP> ergs<SUP>-1</SUP>) matches that of SXR microflares
  in the energy range of 10<SUP>26</SUP>-10<SUP>29</SUP>, and exceeds
  that of nonthermal energies of larger flares observed in HXR by a
  factor of 3-10 (in the energy range of 10<SUP>29</SUP>-10<SUP>32</SUP>
  ergs). Discrepancies of the power-law slope with other studies, which
  report higher values in the range of a=2.0-2.6 (Krucker &amp; Benz;
  Parnell &amp; Jupp), are attributed to methodical differences in the
  detection and discrimination of EUV microflares, as well as to different
  model assumptions in the calculation of the electron density. Besides
  the insufficient power of nanoflares to heat the corona, we find also
  other physical limits for nanoflares at energies &lt;~10<SUP>24</SUP>
  ergs, such as the area coverage limit, the heating temperature limit,
  the lower coronal density limit, and the chromospheric loop height
  limit. Based on these quantitative physical limitations, it appears
  that coronal heating requires other energy carriers that are not
  luminous in EUV, SXR, and HXR.

Title: The Scaling of Solar Flare Hard X-ray Emission to Other
    Flaring Objects in the Universe
Authors: Martens, P. C. H.
Bibcode: 2000IAUS..195..133M
Altcode:
  Fletcher &amp; Martens have successfully modeled solar hard X-ray
  sources observed at the top and footpoints of flaring magnetic loops
  with a Fokker-Planck type particle transport code. I show here that
  there are invariances in the Fokker-Planck equations that make these
  results applicable to environments with vastly different physical
  parameters, such as hard X-ray flares in accretion disks in active
  galactic nuclei, and in RS CVn and ALGOL type binaries.

Title: Having Our Cake and Eating it, Too: Fast Imaging Spectroscopy
    With a Multi-Order Slitless Spectrograph
Authors: Kankelborg, C. C.; Longcope, D. W.; Martens, P. C. H.
Bibcode: 2000SPD....3102101K
Altcode: 2000BAAS...32..829K
  We describe a new type of EUV imaging spectrograph that combines high
  spectral, spatial and temporal resolution. The instrument consists of
  a slitless spectrograph with cameras placed at several diffraction
  orders. The unique information derived from simultaneous imaging
  at multiple orders allows the deconvolution of spectral and spatial
  information, thus overcoming the limitations of a traditional slitless
  spectrograph.

Title: Highly Energetic Physical Processes and Mechanisms for Emission
    from Astrophysical Plasmas
Authors: Martens, P. C. H.; Tsuruta, S.; Weber, M. A.
Bibcode: 2000IAUS..195.....M
Altcode:
  No abstract at ADS

Title: Chromospheric Damping of Alfvén Waves
Authors: De Pontieu, B.; Martens, P. C. H.; Hudson, H. S.
Bibcode: 2000SPD....31.0131D
Altcode: 2000BAAS...32..806D
  We study the damping of Alfvén mode oscillations on coronal loops and
  in the chromosphere. First we consider damping of standing waves on
  coronal loops, such as those observed in the aftermath of a flare with
  the Transition Region and Coronal Explorer (TRACE). We calculate the
  leakage of wave energy from the coronal volume through the footpoints
  of a coronal loop, assuming constant Alfvén speed v<SUB>A</SUB> in
  the corona and v<SUB>A</SUB> varying exponentially with height in the
  photosphere/chromosphere at both ends of the loop. We study analytically
  the influence of chromospheric damping of standing waves on a coronal
  loop and find that, for a moderate amount of chromospheric damping,
  the footpoint leakage can be enhanced. The damping in the partially
  ionized chromosphere is mostly due to collisions between ions and
  neutrals. In a second part we calculate the damping time for Alfvén
  waves of a given frequency, propagating through (model) chromospheres
  of various solar structures such as active region plage, quiet sun
  and the penumbra and umbra of sunspots. For a given wave frequency,
  the maximum damping always occurs at temperature minimum heights
  and in the coldest structure(s), i.e. the umbra of a sunspot. Energy
  dissipation due to ion-neutral damping of Alfvén waves could play a
  considerable role in the energy balance of umbrae, quiet sun and plage
  for wave periods of the order, respectively, 100, 10 and 1 s.

Title: Dynamics in Restructuring Active Regions Observed During
    Soho/Yohkoh/Gbo Campaigns
Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta,
   N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N.
Bibcode: 2000AdSpR..25.1879S
Altcode:
  JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration
  with Yohkoh/SXT and ground based observatories (GBO's), dedicated to
  observe dynamical events through the atmosphere. During runs of these
  programs we observed in restructuring active regions (ARs), surges,
  subflares, bright knots, but not large flares and jets. From these
  observations we have been able to derive some of the responses of the
  coronal and chromospheric plasma to the evolution of the photospheric
  magnetic field. Emerging flux in an AR led to the formation of Arch
  Filament Systems in the chromosphere, hot loops and knots in the
  transition region, and X-ray loops. Frequent surges have been observed
  in relation to parasitic or mixed polarities, but coronal jets have not
  yet been found. We discuss the possible mechanisms acting during the
  restructuring of the active regions (reconnection or ``sea-serpent''
  geometries)

Title: Coronal Heating by Resonant Absorption: The Effects of
    Chromospheric Coupling
Authors: Beliën, A. J. C.; Martens, P. C. H.; Keppens, R.
Bibcode: 1999ApJ...526..478B
Altcode:
  We present the first 2.5 dimensional numerical model calculations
  of the nonlinear wave dynamics and heating by resonant absorption
  in coronal loops with thermal structuring of the transition region
  and higher chromosphere. The numerical calculations were done with
  the Versatile Advection Code. The transition region can move freely
  and is transparent for mass motions from chromosphere to corona. The
  loops are excited at the chromospheric level by linearly polarized
  monochromatic Alfvén waves. We find that the efficiency of resonant
  absorption can be much lower than in equivalent line-tied coronal
  loop models. The inefficiency is due to the fast rate at which slow
  magnetosonic waves are nonlinearly generated in the chromosphere
  and transition region. This leads to considerable transfer of energy
  from the Alfvén wave to the magnetosonic waves. Consequently, only a
  relatively small fraction of the Poynting flux that is injected into
  the loop system at the chromospheric level is available at the coronal
  level. Cavity leakage and detuning also have a negative impact on the
  efficiency, but less so than the nonlinear energy transfer. Inclusion
  of radiative and conductive losses improves the efficiency of resonant
  absorption. While the efficiency of resonant absorption heating is low,
  our results indicate that heating by compression and dissipation of the
  slow magnetosonic waves and shocks can easily lead to a temperature rise
  of a few percent, and for larger driver amplitudes even to a rise over
  10%. Hence, our results support the idea of indirect coronal heating
  through the nonlinear generation of magnetosonic waves that was put
  forward more than 20 yr ago. Furthermore, the large transition region
  and coronal density oscillations that are associated with the slow
  magnetosonic waves provide an explanation for some observed coronal
  and transition region loop extreme-ultraviolet intensity variations.

Title: The Dynamical Influence Of The Transition Region And
    Chromosphere On The Heating Of Coronal Loops By Resonant Absorption
    Of Alfvén Waves
Authors: Belien, A. J. C.; Martens, P. C. H.; Keppens, R.
Bibcode: 1999ESASP.446..167B
Altcode: 1999soho....8..167B
  We present a numerical MHD study of coronal heating by resonant
  absorption of Alfvén waves using models that include an extended
  chromosphere and dynamical transition region. The calculations are
  done with the Versatile Advection Code (VAC) and assume axisymmetric
  loop configurations. Linear polarized, monochromatic Alfvén waves are
  launched at the bottom of our extended chromosphere. The efficiency of
  heating by resonant absorption of these waves in the corona is measured
  by the ratio of Ohmic dissipation over the incoming Poyting flux at
  the bottom of our chromosphere (averaged over a driving period). The
  efficiency turns out to be much smaller than in loop models that
  do not take the chromospheric and transition region coupling into
  account. For our model, the efficiency is typically of the order of 10%
  in contrast with values over 90% in models without the coupling taken
  into account. The difference can be described in terms of efficient
  nonlinear generation of compressive motions in the chromosphere
  and transition region, the change of the coronal cavity length as a
  consequence of the continuous motion of the transition region (due to
  the the Alfvén wave pressure and compressive motions), and coronal
  cavity leakage due to a finite Alfvén speed ratio between corona
  and chromosphere. The compressive waves and motions lead to density
  variations that should be observable. To proove that, our model results
  are used to simulate some coronal and transition region CDS EUV line
  observations as well as broad band EIT observations. The results are
  used to give an explanation of EUV coronal brightenings in terms of
  mass motions.

Title: Wave Heating and Nonlinear Dynamics of Coronal Loops
Authors: Beliën, A. J. C.; Martens, P. C. H.; Keppens, R.; Tóth, G.
Bibcode: 1999ASPC..184..248B
Altcode:
  We present the first results of 2.5D nonlinear magnetohydrodynamic
  wave heating simulations of solar coronal loops with inclusion
  of the modeling of the coupling to the transition region and
  chromosphere. Magnetic flux tubes with fixed lengths are considered
  but the coronal extent of the loops as situated in between the two
  transition regions can vary dynamically. The numerical simulations
  were carried out with the Versatile Advection Code. The loops are
  excited with linearly polarized Alfvén waves at the chromospheric
  base. The main finding is that resonant absorption is not efficient
  since most of the Poynting flux that enters the loop will be used to
  support all the nonlinearly generated magnetoacoustic motions and the
  corresponding compression of coronal plasma.

Title: On the Nature of the "Moss" Observed by TRACE
Authors: Martens, P. C. H.; Kankelborg, C. C.
Bibcode: 1999AAS...194.7903M
Altcode: 1999BAAS...31..963M
  Moss is the name given to low lying ( 2 Mm), hot ( 1 MK) plasma that
  has recently been observed by the Transition Region and Coronal
  Explorer (TRACE). The moss occurs over some but not all magnetic
  plage. We investigate two hypotheses regarding the nature of the moss:
  (1) emission from small, million degree loops; (2) emission from the
  legs of 2-5 million degree loops. An analytical loop model is used to
  demonstrate that only the second hypothesis is consistent with the
  observations. It is shown that the observed brightness of the moss
  should scale as the third power of the loop maximum temperature.

Title: Can Streamer Blobs Prevent the Buildup of the Interplanetary
    Magnetic Field?
Authors: van Aalst, M. K.; Martens, P. C. H.; Beliën, A. J. C.
Bibcode: 1999ApJ...511L.125V
Altcode: 1998astro.ph.12099V
  Coronal mass ejections continuously drag closed magnetic field lines
  away from the Sun, adding new flux to the interplanetary magnetic field
  (IMF). We propose that the outward-moving blobs that have been observed
  in helmet streamers are evidence of ongoing, small-scale reconnection
  in streamer current sheets, which may play an important role in the
  prevention of an indefinite buildup of the IMF. Reconnection between
  two open field lines from both sides of a streamer current sheet
  creates a new closed field line, which becomes part of the helmet,
  and a disconnected field line, which moves outward. The blobs are
  formed by plasma from the streamer that is swept up in the trough of
  the outward-moving field line. We show that this mechanism is supported
  by observations from Solar and Heliospheric Observatory (SOHO)/Large
  Angle and Spectrometric Coronagraph. Additionally, we propose a thorough
  statistical study to quantify the contribution of blob formation to the
  reduction of the IMF and indicate how this mechanism may be verified
  by observations with SOHO/Ultraviolet Coronagraph Spectrometer and the
  proposed NASA Solar Terrestrial Relations Observatory and ESA Polar
  Orbiter missions.

Title: Scientific highlights from the Solar and Heliospheric
    Observatory
Authors: Martens, P. C. H.; Muglach, K.
Bibcode: 1999ASSL..243..325M
Altcode: 1999sopo.conf..325M
  No abstract at ADS

Title: Energy and momentum deposition in coronal holes. Solar
    coronal hole simulations compared with interpretations of YOHKOH
    SXT observations
Authors: Tziotziou, K.; Martens, P. C. H.; Hearn, A. G.
Bibcode: 1998A&A...340..203T
Altcode:
  A grid of 74 coronal models with parameterized heating distribution,
  representing a wide range of physical parameters, has been
  calculated. We find that three of these models reproduce the recent
  observations made by Hara et al. (\cite{hara:tsun}) with the soft
  X-ray telescope aboard the Japanese satellite Yohkoh, which indicate
  a temperature of 1.8 ~ 2.4 x es 10(6) { K with an emission measure
  of 10(25.5) to 10(26.2) cm^{-5}, while other solutions reproduce the
  more standard Yohkoh and Skylab observations, which have a temperature
  of about 1.4 x es 10(6) { K The best fit for the coronal temperature
  and emission measure gives a velocity at the Earth's orbit of only
  10 {km s^{-1}. A model including acceleration by Alfven waves gives
  a final velocity of 630 km s^{-1} which is in agreement with the
  observations. The mechanical heating flux at the transition region
  is 2.1 x es 10(5) ergcms with a weighted average dissipation scale
  length of 0.1 R_{\odot}. The flux of Alfven waves is 1 x es 10(5)
  ergcms . In our models the velocity of the solar wind from coronal
  holes is completely determined by the Alfven wave acceleration, in
  contrast to previous models in which the Alfven wave acceleration
  increased the velocity of the purely thermal model only by a factor
  2. Observations of the non thermal broadening of the coronal red and
  green lines are consistent with this model.

Title: Reconnection, Particle Acceleration, and Hard X-ray Emission
    in Eruptive Solar Flares
Authors: Martens, Petrus C.
Bibcode: 1998APS..DPP.C2M04M
Altcode:
  The frequent occurrence of Hard X-ray emission from the top of flaring
  loops was one of the discoveries by the Hard X-ray telescope on board
  the Japanese Yohkoh satellite. I will show how the combined effect of
  magnetic field convergence and pitch- angle scattering of non-thermal
  electrons injected at the top of the loop results in the generation of
  looptop sources with properties akin to those observed by Yohkoh. In
  addition it is shown that the injection of proton beams in the loop
  legs, expected from theory, reproduces the observed high temperature
  ``ridges" in the loop legs by mirroring and energy loss through
  collisions. I will interpret these numerical results as supporting the
  now widely accepted model of an erupting magnetic flux tube generating
  a reconnecting current sheet in its wake, where most of the energy
  release takes place. The strong similarity with the reconnection
  observed in the MRX experiment in Princeton will be analyzed in detail.

Title: A Model for Hard X-Ray Emission from the Top of Flaring Loops
Authors: Fletcher, L.; Martens, P. C. H.
Bibcode: 1998ApJ...505..418F
Altcode:
  The frequent occurrence of hard X-ray emission from the top of
  flaring loops was one of the discoveries by the Hard X-Ray Telescope
  on board the Japanese Yohkoh satellite. In this paper we take a flare
  current-sheet geometry and show how the combined effect of magnetic
  field convergence and pitch-angle scattering of nonthermal electrons
  injected at the top of the loop results in the generation of a looptop
  source with properties akin to those observed by Yohkoh. We demonstrate
  that a looptop source can be produced in both impulsive and gradual
  phase loops. We further present a possible mechanism for the generation
  of high-temperature ``ridges'' in the loop legs.

Title: An approximate self-consistent theory of the magnetic field
    of fluted penumbrae
Authors: Neukirch, T.; Martens, P. C. H.
Bibcode: 1998A&A...332.1075N
Altcode: 1997astro.ph.11351N
  A self-consistent mathematical description of the magnetic field of
  fluted sunspot penumbrae is presented. This description is based on
  an expansion of the nonlinear force-free magnetohydrostatic equations
  written in cylindrical coordinates. The lowest order solutions are
  mathematically equivalent %similar to laminated force-free equilibria
  in Cartesian geometry. The lowest order solutions have no toroidal
  component of the magnetic field and the magnetic pressure does not
  vary with azimuth but the solutions allow arbitrary variations of
  the magnetic field components with azimuth. Explicit solutions are
  presented which have a realistic radial profile of the magnetic field
  strength and reproduce the basic features of the observations.

Title: SOHO - YOHKOH Science Collaboration
Authors: Martens, P. C.
Bibcode: 1998ASSL..229..217M
Altcode: 1998opaf.conf..217M
  No abstract at ADS

Title: Hard X-Ray Emission from a Mirror Trap at the Top of
    Reconnecting Loops
Authors: Martens, P. C. H.; Fletcher, L.
Bibcode: 1998ASSL..229..269M
Altcode: 1998opaf.conf..269M
  No abstract at ADS

Title: MHD and Plasma Interpretation of a Prominence Eruption Observed
    by SOHO (Review)
Authors: Martens, P. C. H.
Bibcode: 1998ASPC..150..294M
Altcode: 1998IAUCo.167..294M; 1998npsp.conf..294M
  No abstract at ADS

Title: Filament Disparition Brusque and CME - September 25-26,
    1996 Event
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.;
   Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson,
   B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka,
   Y.; Nitta, N.
Bibcode: 1998ASPC..150..366V
Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V
  No abstract at ADS

Title: Surges and filaments in active regions during SOHO campaigns
Authors: Schmieder, B.; Deng, Y.; Rudawy, P.; Nitta, N.; Mandrini,
   C. H.; Fletcher, L.; Martens, P.; Innes, D.; Young, P.; Mason, H.
Bibcode: 1998ESASP.421..323S
Altcode: 1998sjcp.conf..323S
  No abstract at ADS

Title: Foreword
Authors: Koutchmy, S.; Martens, P.; Shibata, K.
Bibcode: 1998ESASP.421...14K
Altcode: 1998sjcp.conf...14K
  No abstract at ADS

Title: Coordinated Eclipse and SOHO Observations on 26 February 1998
Authors: Muglach, B. Foing K.; Beaufort, T.; Orlando, S.; Martens,
   P.; Desteve, C.
Bibcode: 1998ESASP.417..337M
Altcode: 1998cesh.conf..337M
  No abstract at ADS

Title: A SOHO User Manual
Authors: Martens, Petrus C.
Bibcode: 1998LNP...507..263M
Altcode: 1998sspt.conf..263M
  This paper is intended to serve as the first version of the "SOHO User
  Manual", a "how to" guide for those interested in analyzing existing
  SOHO data, or proposing new SOHO observations. Questions addressed
  are, how to use the SOHO catalogs, where to find the appropriate data
  analysis software, how to request permission to use proprietary data,
  how to propose and prepare SOHO observing programs.

Title: Solar Coronal Heating: AC versus DC
Authors: Milano, Leonardo J.; Gómez, Daniel O.; Martens, Petrus C. H.
Bibcode: 1997ApJ...490..442M
Altcode:
  The heating of the plasma confined in active regions of the solar
  corona is caused by the dissipation of magnetic stresses induced
  by the photospheric motions of the loop footpoints. The aim of the
  present paper is to analyze whether solar coronal heating is dominated
  by slow (DC) or rapid (AC) photospheric driving motions. We describe
  the dynamics of a coronal loop through the reduced magnetohydrodynamic
  equations and assume a fully turbulent state in the coronal plasma. The
  boundary condition for these equations is the subphotospheric velocity
  field that stresses the magnetic field lines, thus replenishing
  the magnetic energy that is continuously being dissipated inside the
  corona. In a turbulent scenario, energy is efficiently transferred by a
  direct cascade to the microscale, where viscous and Joule dissipation
  take place. Therefore, for the macroscopic dynamics of the fields,
  the net effect of turbulence is to produce a dramatic enhancement of
  the dissipation rate. This effect of the microscale on the macroscale
  is modeled through effective dissipation coefficients much larger than
  the molecular ones. We consistently integrate the large-scale evolution
  of a coronal loop and compute the effective dissipation coefficients
  by applying a closure model (the eddy-damped, quasi-normal Markovian
  approximation). For broadband power-law photospheric power spectra,
  the heating of coronal loops is DC dominated. Nonetheless, a better
  knowledge of the photospheric power spectrum as a function of both
  frequency and wavenumber will allow for more accurate predictions of
  the heating rate from this simple model.

Title: The Solar and Heliospheric Observatory (SOHO) in 1996.
Authors: Domingo, V.; Fleck, B.; Martens, P.; Sanchez, L.
Bibcode: 1997joso.proc....4D
Altcode:
  This report gives a brief overview of SOHO's scientific production in
  its first year of operation.

Title: An Analytical Model for Fluted Sunspots and a New
    Interpretation of Evershed Flow and X-Ray Anemones
Authors: Martens, Petrus C. H.; Hurlburt, Neal E.; Title, Alan M.;
   Acton, Loren W.
Bibcode: 1996ApJ...463..372M
Altcode:
  We present a force-free constant-α model for the magnetic field in and
  above so-called "fluted" sunspots. This model is motivated by recent
  high-resolution observations of Title et al. at the Swedish Solar
  Observatory in La Palma. They observed that the inclination angle of
  the magnetic field in the penumbra of sunspots oscillates rapidly
  with azimuth, with a period of about 60 and an amplitude of about
  18°. They further find that there is little variation in the radial
  direction and in absolute field strength. The resulting phenomenon
  of interlocking high- and low-inclination field lines was called
  "flutedness. <P />In our model, the parameters are chosen to reproduce
  the La Palma magnetograms, and an analytical expression is obtained for
  the three-dimensional magnetic field emanating from the sunspot's umbra
  and penumbra. The model correctly reproduces the azimuthal variation in
  inclination angle, as well as the mean constancy of the magnetic field
  strength, and the appearance of a highly corrugated neutral line on
  the limb side of off-center sunspots. We find that the "flutedness"
  results in a highly complex topology in a boundary layer extending
  from the photo sphere into the chromosphere, while the coronal field is
  uniform. <P />Title et al. demonstrated that the Evershed flow occurs
  in regions of nearly horizontal magnetic field, and tacitly assumed,
  as is done in most of the literature, that the dark filaments in which
  the flow is observed form individual magnetic flux tubes. Our magnetic
  field solution suggests that the regions of nearly horizontal field
  at the photo spheric boundary may not form individual magnetic flux
  tubes, but rather a series of short horizontal loops bridging a neutral
  line that is stretched in the radial direction along the penumbra,
  up to the outer penumbral boundary. Hence, the Evershed flow could not
  be a simple siphon flow in the radial direction, but would consist of
  phase-coordinated flows along the many short loops bridging the neutral
  line. However, the assumption of a force-free field breaks down in
  this region of the atmosphere, and the topology suggested by it may
  not materialize in reality. <P />We further demonstrate that there
  are large variations in the photospheric cross sections of coronal
  loops, due to the complexity of the field near their photospheric
  footpoints. Under the assumption of constant energy input per unit
  surface area into these loops, the variation in cross section is
  qualitatively consistent with the variation in X-ray brightness of
  loops in penumbral "anemones" observed by Yohkoh.

Title: High resolution Lyalpha images obtained with the transition
region camera (TRC): a comparison with Hα observations
Authors: Wiik, J. E.; Foing, B. H.; Martens, P.; Fleck, B.;
   Schmieder, B.
Bibcode: 1996AdSpR..17d.105W
Altcode: 1996AdSpR..17..105W
  Comparing high spatial resolution (~ 1'') images observed in Lyalpha
  with the Transition Region Camera (TRC) and in Hα at Sacramento Peak
  and Meudon Observatories, we notice that some structures are well
  correlated in the two lines (plages), while others are less correlated
  (chromospheric network, filaments). This is an indication of the
  inhomogeneous distribution of physical parameters in these structures.

Title: On Small Coronal Particle Acceleration Sites with Widespread
    Magnetic Connections
Authors: Aurass, H.; Klein, K. -L.; Martens, P. C. H.
Bibcode: 1996ASPC..111..194A
Altcode: 1997ASPC..111..194A
  For the 25 October 1994 flare in NOAA AR 7792, the authors present
  radio spectral, radio imaging and Yohkoh SXT observations revealing
  features of reconnection and energy release in coronal structures.

Title: SOHO Ground Segment, Science Operations, and Data Products
Authors: St. Cyr, O. C.; Sánchez-Duarte, L.; Martens, P. C. H.;
   Gurman, J. B.; Larduinat, E.
Bibcode: 1995SoPh..162...39S
Altcode:
  We describe the ground segment, pre-launch operations concepts, and
  data products supporting the SOHO mission. Our goal is threefold:
  first, we provide a historical view of the design and development of
  the systems described here, as a background perspective to those who
  will use the system and those who may build such systems for future
  missions. Second, because we hope that many researchers from the solar
  and space physics communities will visit these facilities during the
  mission, we provide an overview for the benefit of the end-user. We
  anticipate that visitors to GSFC may plan observations for one or more
  of SOHO's complement of instruments, and such researchers may use the
  facilities to analyze data gathered by the SOHO instruments. Third,
  we present the working plan for investigators with groundbased or
  other spacebased instruments to collaborate with SOHO.

Title: The point spread function of the soft X-ray telescope aboard
    Yohkoh
Authors: Martens, Petrus C.; Acton, Loren W.; Lemen, James R.
Bibcode: 1995SoPh..157..141M
Altcode:
  The point spread function of the SXT telescope aboardYohkoh has been
  measured in flight configuration in three different X-ray lines
  at White Sands Missile Range. We have fitted these data with an
  elliptical generalization of the Moffat function. Our fitting method
  consists of χ<SUP>2</SUP> minimizationin Fourier space, especially
  designed for matching of sharply peaked functions. We find excellent
  fits with a reduced χ<SUP>2</SUP> of order unity or less for single
  exposure point spread functions over most of the CCD. Near the edges
  of the CCD the fits are less accurate due to vignetting. From fitting
  results with summation of multiple exposures we find a systematic
  error in the fitting function of the order of 3% near the peak of the
  point spread function, which is close to the photon noise for typical
  SXT images in orbit. We find that the full width to half maximum and
  fitting parameters vary significantly with CCD location. However, we
  also find that point spread functions measured at the same location
  are consistent to one another within the limit determined by photon
  noise. A `best' analytical fit to the PSF as function of position
  on the CCD is derived for use in SXT image enhancement routines. As
  an aside result we have found that SXT can determine the location of
  point sources to about a quarter of a 2.54 arc sec pixel.

Title: Preparing for SOHO: results from the transition region camera
Authors: Wiik, J. E.; Foing, B. H.; Schmieder, B.; Martens, P.;
   Fleck, B.
Bibcode: 1994ESASP.373..433W
Altcode: 1994soho....3..433W
  No abstract at ADS

Title: First Detection of Correlated Electron Beams and Plasma Jets
    in Radio and Soft X-Ray Data
Authors: Aurass, H.; Klein, K. -L.; Martens, P. C. H.
Bibcode: 1994SoPh..155..203A
Altcode:
  From a common analysis of solar radio spectral and imaging data of a
  fast drift burst of type U(N) together with Yohkoh soft X-ray images
  it is shown that the radio emission is compatible with electron beams
  injected and reflected in extended loops. The electron beam production
  coincides with the injection of hot matter, visible as a jetlike soft
  X-ray feature in the underlying loop system.

Title: Material Ejection
Authors: Webb, David F.; Forbes, Terry G.; Aurass, Henry; Chen, James;
   Martens, Piet; Rompolt, Bogdan; Rusin, Vojtech; Martin, Sara F.
Bibcode: 1994SoPh..153...73W
Altcode:
  This paper reviews the major discussions and conclusions of the Flares
  22 Workshop concerning the physical processes involved in mass ejecta
  events, with an emphasis on large-scale phenomena, especially Coronal
  Mass Ejections (CMEs). New insights have been gained from recent
  data obtained from the SMM andYohkoh spacecraft and from several new
  ground-based radio and optical instruments, as well as from theoretical
  advances concerning the origins, driving mechanisms and long-term
  evolution of CMEs.

Title: Possible detection of a stellar flare-generated particle beam
    in polarized light
Authors: Saar, S. H.; Martens, P. C. H.; Huovelin, J.; Linnaluoto, S.
Bibcode: 1994A&A...286..194S
Altcode:
  We present broadband linear polarization measurements of the active
  dK5e flare star, BD +26 730, which show a rapid change in polarization
  amplitude and direction over a two hour period. We conclude that
  impact polarization resulting from flare-generated particle beams
  is the most likely cause of the polarization variations. If this
  interpretation is correct, this event represents the most direct
  evidence to date for flare-generated particle beams in a star other
  than the Sun. With proton beams as the most probable source, energy
  fluxes of the order of 10^9-10^ erg/cm2/s are required to power the
  observed polarization changes. Using the non-flare polarization level
  (likely produced by stellar magnetic regions) and simple models,
  we estimate a lower limit of 7% for the inhomogeneous component of
  the magnetic region area filling factor. We compare our results with
  solar flares and suggest future observational and theoretical efforts.

Title: Electric Currents and Coronal Heating in NOAA Active Region
    6952
Authors: Metcalf, T. R.; Canfield, R. C.; Hudson, H. S.; Mickey,
   D. L.; Wulser, J. -P.; Martens, P. C. H.; Tsuneta, S.
Bibcode: 1994ApJ...428..860M
Altcode:
  We examine the spatial and temporal relationship between coronal
  structures observed with the soft X-ray telescope (SXT) on board the
  Yohkoh spacecraft and the vertical electric current density derived from
  photospheric vector magnetograms obtained using the Stokes Polarimeter
  at the Mees Solar Observatory. We focus on a single active region:
  AR 6952 which we observed on 7 days during 1991 December. For 11
  independent maps of the vertical electric current density co-aligned
  with non-flaring X-ray images, we search for a morphological
  relationship between sites of high vertical current density in the
  photosphere and enhanced X-ray emission in the overlying corona. We
  find no compelling spatial or temporal correlation between the sites of
  vertical current and the bright X-ray structures in this active region.

Title: An Analytical Model for Fluted Sunspots and its Relation with
    Evershed Flow and X-Ray Anemone
Authors: Hurlburt, Neal E.; Martens, Petrus C.; Title, Alan M.;
   Acton, Loren
Bibcode: 1994ASPC...68..300H
Altcode: 1994sare.conf..300H
  No abstract at ADS

Title: Volume Reconstruction of Magnetic Fields using Solar Imagery
Authors: Hurlburt, Neal E.; Martens, Petrus C. H.; Slater, Gregory L.;
   Jaffey, Steven M.
Bibcode: 1994ASPC...68...30H
Altcode: 1994sare.conf...30H
  No abstract at ADS

Title: A Simple Circuit Model for the December 2 1991 Flare
Authors: Martens, P. C. H.; Tsuneta, S.
Bibcode: 1994xspy.conf..327M
Altcode:
  No abstract at ADS

Title: Morphological Evolution of the Post-Flare Loops of June
    25-26, 1992
Authors: Anwar, B.; Hiei, E.; Hudson, H. S.; Acton, L. W.; Metacalf,
   T.; Lemen, J.; Martens, P.
Bibcode: 1994xspy.conf..121A
Altcode:
  No abstract at ADS

Title: An analytical model for fluted sunspots and a new
    interpretation of Evershed flow
Authors: Martens, P. C.; Hurlburt, N.; Title, A. M.; Acton, L. A.
Bibcode: 1994ASIC..433..237M
Altcode:
  No abstract at ADS

Title: Electric Currents and Coronal Structures in NOAA Active
    Region 6952
Authors: Metcalf, T. R.; Canfield, R. C.; Hudson, H. S.; Mickey,
   D. L.; Martens, P. C. H.; Tsuneta, S.
Bibcode: 1993BAAS...25.1179M
Altcode:
  No abstract at ADS

Title: A Force-Free Model for Fluted Sunspots
Authors: Martens, P. C. H.; Hurlburt, N.; Title, A. M.
Bibcode: 1993BAAS...25R1218M
Altcode:
  No abstract at ADS

Title: Computed Tomographic Reconstruction of the Soft X-ray Corona
Authors: Hurlburt, N. E.; Martens, P. C. H.; Jaffey, S. M.; Slater,
   G. L.
Bibcode: 1993BAAS...25.1188H
Altcode:
  No abstract at ADS

Title: Normal Incidence X-Ray Telescope Power Spectra of X-Ray
    Emission from Solar Active Regions. I. Observations
Authors: Gomez, Daniel O.; Martens, Petrus C. H.; Golub, Leon
Bibcode: 1993ApJ...405..767G
Altcode:
  Fourier analysis is applied to very high resolution image of coronal
  active regions obtained by the Normal Incidence X-Ray Telescope is
  used to find a broad isotropic power-law spectrum of the spatial
  distribution of soft X-ray intensities. Magnetic structures of all
  sizes are present down to the resolution limit of the instrument. Power
  spectra for the X-ray intensities of a sample of topologically different
  active regions are found which fall off with increasing wavenumber
  as 1/k-cubed. A model is presented that relates the basic features
  of coronal magnetic fluctuations to the subphotospheric hydrodynamic
  turbulence that generates them. The model is used to find a theoretical
  power spectrum for the X-ray intensity which falls off with increasing
  wavenumber as 1/k-cubed. The implications of a turbulent regime in
  active regions are discussed.

Title: Normal Incidence X-Ray Telescope Power Spectra of X-Ray
    Emission from Solar Active Regions. II. Theory
Authors: Gomez, Daniel O.; Martens, Petrus C. H.; Golub, Leon
Bibcode: 1993ApJ...405..773G
Altcode:
  In a previous paper, we used the very high resolution images of coronal
  active regions obtained by the Normal Incidence X-Ray Telescope to
  study the size distribution of X-ray-emitting structures. A Fourier
  analysis of these images showed a broad-band, isotropic, power-law
  spectrum for the spatial distribution of soft X-ray intensities. The
  presence of a broad-band spectrum indicates that magnetic structures
  of all sizes are 3" present, at least down to the resolution limit
  of the instrument, which is about ¾". <P />In the present paper, we
  present a model that relates the basic features of coronal magnetic
  fluctuations to the subphotospheric hydrodynamic turbulence that
  generates them. The main result of this paper is that from this
  model we obtain a theoretical power spectrum for the X-ray intensity,
  which falls off with increasing wavenumber as k<SUP>-3</SUP>, fitting
  remarkably well the observed spectra that we obtained from a sample
  of topologically different active regions. <P />We speculate that the
  nonlinear interactions of these externally driven fluctuations will
  contribute to establish a magnetohydrodynamic turbulent regime in the
  corona. We suggest that the bulk of the energy delivered to the corona
  from footpoint motions directly cascades down to very microscopic length
  scales, where it efficiently dissipates and heats the plasma. However,
  since the wavenumber range associated with the cascade and dissipation
  regions are still beyond present-day spatial resolution limits, the
  presence of a turbulent regime cannot be observationally confirmed.

Title: Book Review: Applying Fractals in Astronomy
Authors: Martens, P. C.; Kleczek, Josip; Heinzel, P.
Bibcode: 1993SoPh..143..401M
Altcode:
  No abstract at ADS

Title: Book-Review: Applying Fractals in Astronomy
Authors: Heck, A.; Perdang, J. M.; Martens, P. C.
Bibcode: 1993SoPh..143..401H
Altcode:
  No abstract at ADS

Title: Yohkoh/SXT Observations and Models For an Eruptive Flare
Authors: Martens, P. C. H.; Tsuneta, S.
Bibcode: 1992AAS...181.5502M
Altcode: 1992BAAS...24.1211M
  On Dec. 2, 1991 Yohkoh/SXT obtained a unique sequence of high quality
  X-ray images of what appeared to be a plasmoid ejection and two-ribbon
  flare, viewed in cross-section on the Solar limb. We will show a
  movie displaying the preflare plasmoid formation, the eruption of the
  plasmoid followed by the onset of the flare, and finally what appears
  to be the formation of postflare loops in a quadrupole type field
  configuration. We have modelled this sequence of events with a simple
  Martens-Kuin circuit approach, approximating the plasmoid/filament
  as a line current, added to a background field consisting of three
  line-dipoles. Overlays of the X-ray movie with the calculated magnetic
  field morphology show excellent agreement, and thus lend further
  credibility to the two-ribbon flare scenario developed by Carmichael,
  Sturrock, Hirayama and many others thereafter.

Title: Erratum - Spatial Power Spectra from YOHKOH Soft X-Ray Images
Authors: Martens, P. C. H.; Gomez, D. O.
Bibcode: 1992PASJ...44..691M
Altcode:
  No abstract at ADS

Title: Spatial Power-Spectra from YOHKOH Soft X-Ray Images
Authors: Martens, Petrus C. H.; Gomez, Daniel O.
Bibcode: 1992PASJ...44L.187M
Altcode:
  We analyze three sequences of images from active regions, and a full
  disk image obtained by Yohkoh's Soft X-ray Telescope. Two sequences
  are from a region at center disk observed through different filters,
  and one sequence is from the limb. After Fourier-transforming the
  X-ray intensity of the images we find nearly isotropic power-spectra
  with an azimuthally integrated slope of -2.1 for the center disk,
  and -2.8 for the limb images. The full-disk picture yields a spectrum
  of -2.4. These results are different from the active region spectra
  obtained with the Normal Incidence X-ray Telescope which have a
  slope of the order of -3.0, and we ascribe this to the difference in
  temperature response between the instruments. However, both the SXT
  and NIXT results are consistent with coronal heating as the endresult
  of a downward quasistatic cascade (in lengthscales) of free magnetic
  energy in the corona, driven by footpoint motions in the photosphere.

Title: Magnetohydrodynamic Non-Equilibrium - a Numerical Experiment
Authors: Martens, P.; Sun, M. T.; Wu, S. T.
Bibcode: 1992LNP...399...65M
Altcode: 1992esf..coll...65M; 1992IAUCo.133...65M
  No abstract at ADS

Title: Spectra of MHD turbulence in the solar corona
Authors: Gomez, D.; Martens, P. C. H.
Bibcode: 1992MmSAI..63..755G
Altcode:
  A theoretical model is presented which relates the basic features of
  coronal MHD turbulence with the subphotospheric HD turbulence that
  drives it. By performing a Kolmogorov-type dimensional analysis, the
  observed power law spectrum was reproduced. The power law was found
  to be independent of the exact subphotospheric power distribution.

Title: Coronal heating through lack of MHD equilibrium
Authors: Martens, P. C. H.; Sun, M. T.; Wu, S. T.
Bibcode: 1992AIPC..267..111M
Altcode: 1992ecsa.work..111M
  We present an analytical example of a series of magnetostatic equilibria
  with an endpoint. Numerical simulation demonstrates that oscillatory
  behavior sets in at the endpoint, with a typical amplitude of 50
  km/sec. We suggest this in situ wave generation is an energy source
  for coronal heating.

Title: Can Yohkoh/SXT observe coronal MHD turbulence?
Authors: Martens, P. C. H.; Gomez, D.
Bibcode: 1992MmSAI..63..759M
Altcode:
  The question of whether the Yokoh Soft-X-ray Telescope (SXT) would
  be sufficiently spatially resolved for observing power spectra of
  the distribution of X-ray intensity was investigated. SXT soft X-ray
  images were simulated by artificially degrading the resolution of the
  digitized Normal Incidence X-ray Telescope X-ray images analyzed by
  Gomez and Martens (1992) were analyzed. Results of spectral analysis
  of the resulting images demonstrate that the Yohkoh SXT will be able
  to observe power spectra over a sufficient range of spatial scales.

Title: Shear-induced instability and arch filament eruption: A
    magnetohydrodynamic (MHD) numerical simulation
Authors: Wu, S. T.; Song, M. T.; Martens, P. C. H.; Dryer, M.
Bibcode: 1991SoPh..134..353W
Altcode:
  We investigate, via a two-dimensional (nonplanar) MHD simulation, a
  situation wherein a bipolar magnetic field embedded in a stratified
  solar atmosphere (i.e., arch-filament-like structure) undergoes
  symmetrical shear motion at the footpoints. It was found that the
  vertical plasma flow velocities grow exponentially leading to a
  new type of global MHD-instability that could be characterized
  as a `Dynamic Shearing Instability', with a growth rate of about
  √8{ovV}<SUB>A</SUB>a, where {ovV}<SUB>A</SUB> is the average Alfvén
  speed and a<SUP>−1</SUP> is the characteristic length scale. The
  growth rate grows almost linearly until it reaches the same order of
  magnitude as the Alfvén speed. Then a nonlinear MHD instability occurs
  beyond this point. This simulation indicates the following physical
  consequences: the central loops are pinched by opposing Lorentz forces,
  and the outer closed loops stretch upward with the vertically-rising
  mass flow. This instability may apply to arch filament eruptions (AFE)
  and coronal mass ejections (CMEs).

Title: A Numerical Experiment on the Origin of MHD Non-Equilibrium
Authors: Martens, P. C. H.; Sun, M. T.; Wu, S. T.
Bibcode: 1991BAAS...23.1035M
Altcode:
  No abstract at ADS

Title: Spectra of MHD Turbulence in the Solar Corona
Authors: Gómez, D.; Martens, P. C. H.
Bibcode: 1991BAAS...23.1062G
Altcode:
  No abstract at ADS

Title: Spectra of MHD Turbulence in Coronal Active Regions (With
    3 Figures)
Authors: Gomez, D.; Martens, P.; Herant, M.; Pardo, F.; Golub, L.
Bibcode: 1991mcch.conf..124G
Altcode:
  No abstract at ADS

Title: SXT Observations of MHD Turbulance in Active Regions
Authors: Martens, P. C. H.; Gómez, D. O.; Slater, G.; Golub, L.
Bibcode: 1991LNP...387..291M
Altcode: 1991fpsa.conf..291M
  The recent discovery from NIXT images that the Fourier transform of
  the X-ray intensity in active regions is a power-law, is consistent
  with 2D MHD turbulence theory. We briefly discuss this theory and its
  application to the heating of the solar corona. Then we demonstrate that
  SXT will be capable of observing similar spectra, even in compressed
  data-transfer mode between flare observations. Finally we discuss
  observing plans for verification of the hypothesis of coronal heating
  through turbulent MHD cascades.

Title: Magnetic Fields in Quiescent Prominences
Authors: van Ballegooijen, A. A.; Martens, P. C. H.
Bibcode: 1990ApJ...361..283V
Altcode:
  The origin of the axial fields in high-latitude quiescent prominences
  is considered. The fact that almost all quiescent prominences obey
  the same hemisphere-dependent rule strongly suggests that the solar
  differential rotation plays an important role in producing the axial
  fields. However, the observations are inconsistent with the hypothesis
  that the axial fields are produced by differential rotation acting on
  an existing coronal magnetic field. Several possible explanations for
  this discrepancy are considered. The possibility that the sign of the
  axial field depends on the topology of the magnetic field in which
  the prominence is embedded is examined, as is the possibility that
  the neutral line is tilted with respect to the east-west direction, so
  that differential rotation causes the neutral line also to rotate with
  time. The possibility that the axial fields of quiescent prominences
  have their origin below the solar surface is also considered.

Title: Neutral Beams in Two-Ribbon Flares and in the Geomagnetic Tail
Authors: Martens, P. C. H.; Young, A.
Bibcode: 1990ApJS...73..333M
Altcode:
  The current sheet created in the wake of an erupting filament during
  a two-ribbon flare is studied. A comparison with the geomagnetic tail
  shows that the physics of these systems is very similar, and therefore
  the existence of super Dreicer fields and the generation of netural
  beams traveling down the postflare loops with small pitch angles may
  be expected. The observational evidence for neutral beams in flares is
  reviewed and found to be generally supportive, while contracting the
  widely held hypothesis of electron beams. A dimensional analysis further
  demonstrates that the results for self-consistent numerical simulations
  of the current sheet in the geomagnetic tail can directly be scaled
  to the coronal current sheet, and the scaling parameters are derived.

Title: Diagnostics for Low Energy Proton Beams in Solar Flares
Authors: Martens, P. C. H.
Bibcode: 1990BAAS...22R.825M
Altcode:
  No abstract at ADS

Title: Observational Evidence for Heating through MHD Turbulence in
    Coronal Active Regions
Authors: Gomez, D.; Martens, P. C. H.; Herant, M.; Golub, L.
Bibcode: 1990BAAS...22Q.796G
Altcode:
  No abstract at ADS

Title: A Numerical Experiment on the Critical Shear in Relation to
    the Non-equilibrium of a Force-free Magnetic Field Evolution
Authors: Sun, M. T.; Wu, S. T.; Martens, P. C. H.
Bibcode: 1990BAAS...22..854S
Altcode:
  No abstract at ADS

Title: A self-consistent model for beam generation in two-ribbon
    flares.
Authors: Martens, P. C. H.
Bibcode: 1990ppsa.conf..259M
Altcode:
  The equations governing the evolution of the current sheet created in
  a solar two-ribbon flare are derived. The finite gyroradius of the
  protons is explicitly accounted for. It is demonstrated that in the
  dimensionless form of these equations the parameters are similar to
  those for the geomagnetic tail. Consequently one can expect a similar
  type of evolution.

Title: Helical flux ropes in solar prominences
Authors: Martens, P. C. H.; van Ballegooijen, A. A.
Bibcode: 1990GMS....58..337M
Altcode:
  The present numerical method for the computation of force-free,
  cancelling magnetic structures shows that flux cancellation at the
  neutral line in a sheared magnetic arcade generates helical field
  lines that can support a prominence's plasma. With increasing flux
  cancellation, the axis of the helical fields moves to greater heights;
  this is suggestive of a prominence eruption. Two alternative scenarios
  are proposed for the formation of polar crown prominences which yield
  the correct axial magnetic field sign. Both models are noted to retain
  the formation of helical flux tubes through flux cancellation as their
  key feature.

Title: NIXT Observations of the June 23 1988 Flare and their
    Theoretical Interpretation
Authors: Martens, P. C. H.; Golub, L.; Herant, M.
Bibcode: 1990ppsa.conf..153M
Altcode:
  No abstract at ADS

Title: A Self Consistent Model for Beam Generation in Two-Ribbon
    Flares.
Authors: Martens, P. C. H.
Bibcode: 1990ppsa.conf..257M
Altcode:
  No abstract at ADS

Title: Time-dependent corona models : scaling laws.
Authors: Korevaar, P.; Martens, P. C. H.
Bibcode: 1989A&A...226..203K
Altcode:
  Scaling laws are derived for the one-dimensional time-dependent Euler
  equations that describe the evolution of a spherically symmetric stellar
  atmosphere. With these scaling laws the results of the time-dependent
  calculations by Korevaar (1989) obtained for one star are applicable
  over the whole Hertzsprung-Russell diagram and even to elliptic
  galaxies. The scaling is exact for stars with the same M/R-ratio and
  a good approximation for stars with a different M/R-ratio. The global
  relaxation oscillation found by Korevaar (1989) is scaled to main
  sequence stars, a solar coronal hole, cool giants and elliptic galaxies.

Title: A Circuit Model for Filament Eruptions and Two-Ribbon Flares
Authors: Martens, P. C. H.; Kuin, N. P. M.
Bibcode: 1989SoPh..122..263M
Altcode:
  We derive a circuit model for solar filament eruptions and two-ribbon
  flares which reproduces the slow energy build up and eruption of the
  filament, and the energy dissipation in a current sheet at the top of
  post-flare loops during the two-ribbon flare. In our model the free
  magnetic energy is concentrated in a current through the filament,
  another current through an underlying current sheet, and surface return
  currents. The magnetic field configuration, generated by these currents
  and a general photospheric background field, has a topology similar
  to the field topology derived from observations.

Title: First Evidence for Particle Beams in a Stellar Flare
Authors: Saar, S. H.; Martens, P.; Huovelin, J.
Bibcode: 1989BAAS...21.1192S
Altcode:
  No abstract at ADS

Title: A Study of Dissipative Structures in the Solar Corona with
    High-Resolution NIXT Images
Authors: Gomez, D.; Martens, P. C. H.; Golub, L.
Bibcode: 1989BAAS...21R1150G
Altcode:
  No abstract at ADS

Title: Numerical Simulation of Well Observed Filament Eruptions
Authors: Martens, P. C. H.; Huang, G.
Bibcode: 1989BAAS...21.1186M
Altcode:
  No abstract at ADS

Title: Formation and Eruption of Solar Prominences
Authors: van Ballegooijen, A. A.; Martens, P. C. H.
Bibcode: 1989ApJ...343..971V
Altcode:
  A model for the magnetic field associated with solar prominences is
  considered. It is shown that flux cancellation at the neutral line of a
  sheared magnetic arcade leads to the formation of helical field lines
  which are capable, in principle, of supporting prominence plasma. A
  numerical method for the computation of force-free, canceling magnetic
  structures is presented. Starting from an initial potential field
  we prescribe the motions of magnetic footpoints at the photosphere,
  with reconnection occurring only at the neutral line. As more and more
  flux cancels, magnetic flux is transferred from the arcade field to
  the helical field. Results for a particular model of the photospheric
  motions are presented. The magnetic structure is found to be stable: the
  arcade field keeps the helical field tied down at the photosphere. The
  axis of the helical field moves to larger and larger height, suggestive
  of prominence eruption. These results suggest that prominence eruptions
  may be trigered by flux cancellation.

Title: Theretical Analysis of the June 23 1988 Flare
Authors: Martens, P. C. H.
Bibcode: 1989BAAS...21..851M
Altcode:
  No abstract at ADS

Title: Proton Acceleration in Solar Flares and in the Geomagnetic
Tail:A Comparison.
Authors: Martens, P. C. H.; Young, A.
Bibcode: 1989npvp.conf..381M
Altcode:
  No abstract at ADS

Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
   Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
   R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
   Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
   J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
   Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
Bibcode: 1989epos.conf....1P
Altcode:
  Contents: 1. Introduction. 2. Magnetohydrodynamic
  instability. 3. Preflare magnetic and velocity fields. 4. Coronal
  manifestations of preflare activity.

Title: The Generation of Neutral Beams in Two-Ribbon Flares
Authors: Young, A.; Martens, P. C. H.
Bibcode: 1988BAAS...20..977Y
Altcode:
  No abstract at ADS

Title: The Generation of Proton Beams in Two-Ribbon Flares
Authors: Martens, P. C. H.
Bibcode: 1988ApJ...330L.131M
Altcode:
  It is shown that, in the current sheet at the top of the arcade
  of postflare loops in a two-ribbon solar flare, particle beams are
  generated by direct electric-field acceleration. The acceleration
  process is completely collisionless and is limited only by the
  gyromotion along the component of the magnetic field perpendicular
  to the sheet. This mechanism is similar to the particle acceleration
  in the geomagnetic tail. Neutral beams emanate from the sheet with
  almost zero pitch angle, making protons the main carriers of the beam
  energy. Approximately 10 to the 35th protons/sec are generated with
  a typical energy of 200 keV. Their energy distribution is a single
  power law, with an upper and lower energy cut-off. Such a population
  is capable of simultaneously generating the observed impulsive-phase
  hard X-rays and the gamma rays.

Title: The generation of proton beams in two-ribbon flares.
Authors: Martens, P. C. H.
Bibcode: 1988sscd.conf..501M
Altcode:
  It is shown that in the current sheet at the top of the arcade of
  postflare loops in a two-ribbon flare, high energy particle beams are
  generated by direct electric field acceleration. The plasma beams in the
  current sheet are completely collisionless, and the acceleration of the
  protons and electrons is limited only by the gyration along the small
  component of the magnetic field perpendicular to the sheet. This process
  is identical with the particle acceleration in the geomagnetic tail.

Title: Direct Electric Field Acceleration in Two-Ribbon Flares
Authors: Martens, P. C. H.; Slater, G. L.
Bibcode: 1987BAAS...19..919M
Altcode:
  No abstract at ADS

Title: The thermal stability of coronal loops by nonlinear diffusion
    asymptotics
Authors: Pakkert, J. W.; Verhulst, F.; Martens, P. C. H.
Bibcode: 1987A&A...179..285P
Altcode:
  The thermal structure of the plasma in coronal loops is
  re-investigated. The authors assume that the plasma is confined to
  move along the field lines because of the high plasma β and study
  the time variability of the temperature structure of the plasma along
  a field line. With the supposition that the evolution of the plasma
  takes place on the thermal timescale, which is much larger than the
  dynamical timescale, they derive a nonlinear reaction-diffusion equation
  (and some additional constraints) that describes the time-dependent
  behaviour of the temperature structure. This equation is studied with
  the use of nonlinear diffusion asymptotics, in particular singular
  perturbation techniques.

Title: Energy conversion in the coronal plasma.
Authors: Martens, P. C. H.
Bibcode: 1986NASCP2442..407M
Altcode: 1986copp.nasa..407M
  Solar and stellar X-ray emission are the observed waste products
  of the interplay between magnetic fields and the motion of stellar
  plasma. Theoretical understanding of the process of coronal heating is
  of utmost importance, since the high temperature is what defines the
  corona in the first place. Most of the research described deals with
  the aspects of the several rivalling theories for coronal heating. The
  rest of the papers deal with processes of energy conversion related
  to flares.

Title: A coordinate free description of magnetohydrostatic equilibria.
Authors: Martens, P. C. H.
Bibcode: 1986NASCP2442..431M
Altcode: 1986copp.nasa..431M
  The question what geometrical restrictions are imposed on static
  magnetic fields by the magnetohydrostatic (MHS) equation is
  addressed. The general mathematical problem is therefore to determine
  the solutions of the MHS equations in the corona subject to an arbitrary
  normal component of the magnetic field at the boundary and arbitrary
  connectivity. What constraints the MHS equations impose on the geometry
  of the solutions, expressed in metric tensors, will be determined.

Title: Coronal manifestations of preflare activity
Authors: Schmahl, E. J.; Webb, D. F.; Woodgate, B.; Waggett, P.;
   Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.;
   Martens, P.
Bibcode: 1986epos.conf.1.48S
Altcode: 1986epos.confA..48S
  A variety of coronal manifestations of precursors or preheating for
  flares are discussed. Researchers found that almost everyone with a
  telescope sees something before flares. Whether an all-encompassing
  scenario will ever be developed is not at all clear at present. The
  clearest example of preflare activity appears to be activated filaments
  and their manifestations, which presumably are signatures of a changing
  magnetic field. But researchers have seen two similar eruptions, one
  without any evidence of emerging flux (Kundu et al., 1985) and the
  other with colliding poles (Simon et al., 1984). While the reconnection
  of flux is generally agreed to be required to energize a flare, the
  emergence of flux from below (at least on short timescales and in
  compact regions) does not appear to be a necessary condition. In some
  cases the cancelling of magnetic flux (Martin, 1984) by horizontal
  motions instead may provide the trigger (Priest, 1985) Researchers
  found similarities and some differences between these and previous
  observations. The similarities, besides the frequent involvement of
  filaments, include compact, multiple precursors which can occur both at
  and near (not at) the flare site, and the association between coronal
  sources and activity lower in the atmosphere (i.e., transition zone
  and chromosphere).

Title: A dynamic model of filament eruptions and two ribbon flares.
Authors: Paul, N.; Kuin, M.; Martens, P. C. H.
Bibcode: 1986NASCP2442..241P
Altcode:
  In this model not only the force balance, but also the energy balance
  of the filament is taken into account. Thus a fully closed system of
  equations is obtained, that describes the evolution of the filament,
  first in force equilibrium during the current build-up phase, then
  in the non-equilibrium phase before the eruption, and the eruption
  itself. A neutral point appears above the photospheric surface in
  the non-equilibrium phase, but long before the eruption. The authors
  find that although the filament itself may be in non-equilibrium,
  the evolution may still be slow up to the height where the eruption
  takes place. The eruption of the filament itself causes a large induced
  electric field at the neutral point which leads to the observed flare
  phenomena.

Title: A dynamic model of filament eruptions and two ribbon flares
Authors: Kuin, N. Paul M.; Martens, Piet C. H.
Bibcode: 1986NASCP2442..241K
Altcode: 1986copp.nasa..241K
  Two basically different models for the filament equilibrium by
  Kippenhahn and Schluter (1957) and Kuperus and Raadu (1974) have
  appeared in the literature. A further analyses by van Tend and Kuperus
  (1978) added the force due to the horizontal component of the background
  field to the Kuperus and Raadu model. In order to obtain a better
  model which actually describes these phenomena, the evolution of the
  filament has to be considered in detail. A first attempt was recently
  presented by Kaastra. Kaastra did not formulate the precise energy
  balance equations for the problem, as is done in the present work. In
  the present model not only the force balance, but also the energy
  balance of the filament is taken into account. Thus a fully closed
  system of equations is obtained, that describes the evolution of the
  filament, first in force equilibrium during the current build-up phase,
  then in the non-equilibrium phase before the eruption, and the eruption
  itself. A neutral point appears above the photospheric surface in the
  non-equilibrium phase, but long before the eruption. It was found that
  although the filament itself may be in non-equilibrium, the evolution
  may still be slow up to the height where the eruption takes place. The
  eruption of the filament itself causes a large induced electric field
  at the neutral point which leads to the observed flare phenomena.

Title: An Electrical Circuit Model for Two-Ribbon Flares
Authors: Martens, P. C. H.; Kuin, N. P. M.
Bibcode: 1986BAAS...18..699M
Altcode:
  No abstract at ADS

Title: Preflare energy build-up in a filament circuit.
Authors: Martens, P. C. H.
Bibcode: 1986SoPh..107...95M
Altcode: 1987SoPh..107...95M
  The two-dimensional Van Tend and Kuperus (1978) scenario for pre-flare
  energy build-up is extended to a fully three-dimensional model and
  applied to the 16 May, 1981 flare observed at Debrecen. It is shown
  that there is plenty of free energy (10<SUP>33</SUP> erg) available
  to explain the ensuing large two-ribbon flare. This estimate is an
  order of magnitude larger than the simple estimate made by Van Tend,
  as a result of the three-dimensional character of the present model. It
  is further confirmed that the global form of the preflare circuit is
  decisive for determining the amount of energy stored in the preflare
  configuration, while the internal structure of the filament is of
  little importance. This is in accordance with the similar claims of
  Alfvén and Van Tend and Kuperus.

Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
   Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
   R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
   Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
   J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
   Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
Bibcode: 1986NASCP2439....1P
Altcode:
  Contents: 1. Introduction: the preflare state - a review of previous
  results. 2. Magnetohydrodynamic instability: magnetic reconnection,
  nonlinear tearing, nonlinear reconnection experiments, emerging flux and
  moving satellite sunspots, main phase reconnection in two-ribbon flares,
  magnetic instability responsible for filament eruption in two-ribbon
  flares. 3. Preflare magnetic and velocity fields: general morphology of
  the preflare magnetic field, magnetic field shear, electric currents in
  the preflare active region, characterization of the preflare velocity
  field, emerging flux. 4. Coronal manifestations of preflare activity:
  defining the preflare regime, specific illustrative events, comparison
  of preflare X-rays and ultraviolet, preflare microwave intensity and
  polarization changes, non-thermal precursors, precursors of coronal
  mass ejections, short-lived and long-lived HXIS sources as possible
  precursors.

Title: Absence of MHS-Equilibrium in Plasmas
Authors: Martens, P. C. H.
Bibcode: 1986mrt..conf...79M
Altcode:
  No abstract at ADS

Title: Book-Review - Magnetic Fields in Astrophysics
Authors: Zeldovich, Y. B.; Ruzmaikin, A. A.; Sokoloff, D. D.; Martens,
   P. C. H.
Bibcode: 1985SoPh...98..195Z
Altcode:
  No abstract at ADS

Title: Book reviews
Authors: Schrijver, J.; Martens, P. C. H.
Bibcode: 1985SoPh...98..195S
Altcode:
  No abstract at ADS

Title: Observations of Steady Anomalous Magnetic Heating in Thin
    Current Sheets
Authors: Martens, P. C. H.; van den Oord, G. H. J.; Hoyng, P.
Bibcode: 1985SoPh...96..253M
Altcode:
  A faint steadily emitting loop-like structure has been observed
  by HXIS in its low energy channels (3.5-8.0 keV) on November 5/6,
  1980. These HXIS observations have permitted us to follow the thermal
  evolution of this loop for a period of about 15 hr and from this study
  we conclude that only a fraction of 0.1% of the volume of the loop is
  steadily heated at the rather large rate of 0.6 erg cm<SUP>-3</SUP>
  s<SUP>-1</SUP>. We interpret this heating as the dissipation of magnetic
  fields in thin current sheets and we find that the dissipation with
  classical resistivity is very unlikely, while ion-kinetic tearing, as
  proposed by Galeev et al. (1981), suits the observations very well. The
  enhancement of the resistivity over the classical resistivity then
  turns out to be a factor 4 × 10<SUP>4</SUP>. Dissipation in extremely
  thin sheets via the ion-acoustic instability (Duijveman et al., 1981)
  cannot be completely excluded when the cross-field heat conductivity
  is anomalously enhanced by a factor 400.

Title: Filament Evolution: Energy Build-Up, Eruption and Oscillations
Authors: Martens, P. C. H.; Kuin, N. P. M.
Bibcode: 1985BAAS...17..592M
Altcode:
  No abstract at ADS

Title: New instabilities in line driven winds.
Authors: Martens, P. C. H.
Bibcode: 1985NASCP2358..226M
Altcode: 1985onhm.rept..226M
  The author proposes a general three-dimensional treatment of the
  stability problem of line-driven stellar winds, which leads to
  the general dispersion equation. From this dispersion equation a
  new instability in stellar winds is derived: the 'thermal drift
  instability'. It is related to changes in absorption of radiation
  caused by temperature perturbations. This mechanism results in growing,
  inwardly propagating sound waves.

Title: Applications of non-linear methods in astronomy
Authors: Martens, P. C. H.
Bibcode: 1984PhR...115..315M
Altcode:
  In this review I discuss catastrophes, bifurcations and strange
  attractors in a non-mathematical manner by giving very simple examples
  that st ill contain the essence of the phenomenon. The salientresults
  of the applications of these non-linear methods in astrophysics
  are reviewed and include such diverse phenomena as solar flares and
  loop brightenings (catastrophes), formation of binaries and cyclic
  stellar winds (bifurcations) and the solar cycle and galactic dynamics
  (strange attractors). Emphasis is laid on the unifying concept of
  non-linearity in (simple) differential equatio ns that can be the
  framework for understanding and predicting such diverse phenomena
  as mentioned above. Finally there is a discussion on the concept of
  intrinsic unpredictability (as a result on non-linearity), the limit
  it sets to the use of numerical models and the way it contradicts our
  intuiti ve notions on deterministic systems. <P />From October 1,
  1984: Laboratory for Astronomy and Solar Physics, Code 682, NASA,
  Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.

Title: Summary of the Workshop, Conclusions - Discussion
Authors: La Dous, C.; Lago, T.; Kuin, P.; Martens, P.; Ramella, M.;
   Company), The
Bibcode: 1984evml.conf..219L
Altcode:
  No abstract at ADS

Title: Book-Review: Solar Magnetohydrodynamics
Authors: Priest, E. R.; Martens, P. C. H.
Bibcode: 1984Ruimt..33..119P
Altcode:
  No abstract at ADS

Title: Relaxation oscillations and double temperature structures in
    stellar coronae.
Authors: Hearn, A. G.; Kuin, N. P. M.; Martens, P. C. H.
Bibcode: 1983A&A...125...69H
Altcode:
  Further work using the iterative method of Hearn and Vardavas (1981)
  for calculating stationary models for stellar coronae has shown that
  the coronae of small extent obtained with large fluxes of mechanical
  energy are not stable. It is suggested that the corona undergoes a
  relaxation oscillation in which a single extended corona collapses to
  a double corona which in turn builds up to a single extended corona
  again. Such a coronal relaxation oscillation may be an explanation
  for the observed variations of mass loss from late B and early A type
  supergiants and perhaps from Be stars. The inclusion of radiative
  forces resulting from the absorption of photospheric radiation by
  resonance lines should increase the period of the oscillation. If
  these radiative forces are sufficiently strong they should stabilize
  the oscillation giving a double corona structure. Such a model could
  in principle explain the observed soft X-ray emission of OB supergiants
  and the discrepancy between mass loss rates deduced from the ultraviolet
  and radio measurements.

Title: The thermal evolution of resonantly heated coronal loops
Authors: Martens, P. C. H.; Kuin, N. P. M.
Bibcode: 1983A&A...123..216M
Altcode:
  The time-dependent model of Kuin and Martens (1982) for the thermal
  structure of the plasma in a coronal loop is extended to account for
  the mechanism of resonant electrodynamic heating (Ionson, 1982). It
  is found that, just as in the models of constant heating of Kuin and
  Martens, the static thermal equilibrium for the loops is unstable
  and that the time dependent solutions for the plasma in a loop are
  cyclic, consisting of a short cool phase and a long hot phase. This
  last phase is almost identical to the static solution and this explains
  the static appearance of a loop. In addition to this cyclic behaviour
  catastrophic transitions in the X-ray emission of a loop may occur, as
  a result of a gradual change in the loop length or the magnetic field
  strength. Finally a comparison is made with the numerical solutions
  for the evolution of the plasma in coronal loops by other authors.

Title: Nonlinearity and Instability in Stellar Coronae
Authors: Martens, P. C. H.
Bibcode: 1983PhDT.......138M
Altcode:
  This thesis consists of three parts. Chapter 2, the first part,
  reviews applications of nonlinear methods in astronomy, in particular
  in stellar coronae. Chapters 3, 4, and 5, the second part, deal with
  various aspects of the acceleration and thermal stability of stellar
  winds, while chapters 6 through 9 consider the thermal structure and
  stability of the plasma in closed coronal loops, such as observed on the
  Sun. All chapters have been published as papers in refereed journals.

Title: Nonlinearity and instability in stellar coronae
Authors: Martens, Petrus Cornelis Hendrik Piet
Bibcode: 1983PhDT.......170M
Altcode:
  No abstract at ADS

Title: A thermal catastrophe in a resonantly heated coronal loop
Authors: Martens, P. C. H.; Kuperus, M.
Bibcode: 1983IAUS..102..397M
Altcode:
  A theory for the thermal stability of hot coronal loops is presented,
  which is based on the resonant electrodynamic heating theory of Ionson
  (1982) and the evaporation/condensation scenario of Krall and Antiochos
  (1980). The theory predicts that gradual changes in the length of
  a loops or in its magnetic field strength can trigger catastrophic
  changes in the X-ray visibility of the loop, without the need for
  a change in the magnetic field topology. A natural explanation is
  thereby given for the observations of X-ray brightenings in loops and
  loop evacuations with coronal rain.

Title: Resonant electrodynamic heating and the thermal stability of
    coronal loops
Authors: Martens, P. C. H.; Kuperus, M.
Bibcode: 1982A&A...113..324M
Altcode:
  The resonant electrodynamic heating theory of Ionson (1982) and the
  evaporation/condensation scenario of Krall and Antiochos (1980) are
  invoked by a theory of hot coronal loop thermal stability. The theory
  predicts that gradual changes in loop length or magnetic field strength
  can trigger catastrophic X-ray visibility changes in the loop without
  accompanying changes in magnetic field topology. This is judged to
  constitute a natural explanation for observed X-ray brightening in
  loops, as well as loop evacuations with coronal rain.

Title: On cool coronal loops
Authors: Martens, P. C. H.; Kuin, N. P. M.
Bibcode: 1982A&A...112..366M
Altcode:
  Analytical model calculations and physical arguments are used to examine
  cool equilibria in coronal loops. Static loop model assumptions include
  a one-dimensional energy equation, a constant cross-sectional area, and
  a loop symmetric top. It is shown, in contradiction to Hood and Priest
  (1979) results, that cool loop maximum height has a minimal dependence
  on the heating mechanism and the radiation losses, and does not depend
  on constants of proportionality. In addition, thermal catastrophe occurs
  not only as a result of loop length variations, but also as a result of
  heating or pressure variations. It is also concluded that for a given
  heating mechanism, thermal catastrophe occurs at only one loop length.

Title: On the thermal stability of hot coronal loops - The coupling
    between chromosphere and corona
Authors: Kuin, N. P. M.; Martens, P. C. H.
Bibcode: 1982A&A...108L...1K
Altcode:
  We consider the interaction of the hot plasma in coronal loops with the
  underlying chromospheric plasma, and find stable static equilibria
  if the coupling between corona and chromosphere is sufficiently
  strong. However, for typical coronal loop conditions the interaction
  is not strong enough for perfect stabilisation and an oscillatory
  solution is found with a period of about a day. The latter solution
  is very similar to the static solution during most of the time and
  is relatively cool only during a short while. We tentatively identify
  this cyclic behaviour with the observed up-flows and downflows in the
  solar corona.

Title: An analytical model for stellar coronae
Authors: Martens, P. C. H.
Bibcode: 1981A&A...102..156M
Altcode:
  A semianalytical model based on the assumption of an isothermal corona
  and a transition region of constant pressure is developed for stationary
  stellar coronae. It is shown that the temperature structure of the
  transition region can be described by a one-parameter differential
  equation, leading to a one-parameter set of solutions for the transition
  region temperature structure. A comparison is also made of the results
  obtained by assuming, first, acoustic heating, and then replacing
  it by constant heating up to an arbitrary height. In the first case,
  it is shown that the period and flux of the sound waves that heat the
  corona are the only external parameters needed to describe the corona
  and transiton region. The second case demonstrates that only the heating
  function needs to be specified in order to obtain a full solution.

Title: Line driven sound waves in early type stars.
Authors: Martens, P. C. H.
Bibcode: 1979A&A....75L...7M
Altcode:
  The existence of rapidly growing sound waves in the expanding
  atmospheres of hot stars is demonstrated. The sound waves are amplified
  by the velocity dependence of the radiative forces associated with the
  impurity ion resonance lines. Strong sound waves with a period of 15
  minutes to several hours may be expected. The estimated acoustic flux
  produced by this mechanism is 8 billion erg/sq cm per sec for Zeta
  Puppis (O4ef) and 700 million erg/sq cm per sec for Epsilon Orionis
  (B0 Ia). This energy may be sufficient to heat a corona.

