A5050485849- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Solar Radiation and Photovoltaics
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Distributed and Parallel Computing Systems
- Astronomy and Astrophysical Research
- Marine and coastal ecosystems
- Oil, Gas, and Environmental Issues
- Magnetic confinement fusion research
- Global Energy and Sustainability Research
- Earthquake Detection and Analysis
- Computational Physics and Python Applications
- Marine Biology and Ecology Research
- Gamma-ray bursts and supernovae
- Scientific Computing and Data Management
- Advanced X-ray Imaging Techniques
- History and Developments in Astronomy
- Spacecraft and Cryogenic Technologies
- Marine and environmental studies
- Geochemistry and Geologic Mapping
- Image Retrieval and Classification Techniques
Georgia State University
2014-2024
Athena Research and Innovation Center In Information Communication & Knowledge Technologies
2022
Georgia Southern University
2015
Montana State University
2004-2014
Center for Astrophysics Harvard & Smithsonian
1990-2014
University of Manitoba
2008-2014
Maastricht University
2013
American University of the Caribbean School of Medicine
2013
Harvard University
1989-2010
Smithsonian Astrophysical Observatory
2008-2010
view Abstract Citations (734) References (66) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Formation and Eruption of Solar Prominences van Ballegooijen, A. ; Martens, P. C. H. A model for the magnetic field associated with solar prominences is considered. It shown that flux cancellation at neutral line a sheared arcade leads to formation helical lines which are capable, in principle, supporting prominence plasma. numerical method computation force-free,...
We present a detailed analysis of the geometric and physical parameters 281 EUV nanoflares, simultaneously detected with TRACE telescope in 171 195 Å wavelengths. The detection discrimination these flarelike events is first paper this series. determine loop length l, width w, emission measure EM, evolution electron density ne(t) temperature Te(t), flare decay time τdecay, calculate radiative loss τloss, conductive τcond, thermal energy Eth. findings are as follows: (1) nanoflares range...
In Fall 2008 NASA selected a large international consortium to produce comprehensive automated feature-recognition system for the Solar Dynamics Observatory (SDO). The SDO data that we consider are all of Atmospheric Imaging Assembly (AIA) images plus surface magnetic-field from Helioseismic and Magnetic Imager (HMI). We robust, very efficient, professionally coded software modules can keep up with stream detect, trace, analyze numerous phenomena, including flares, sigmoids, filaments,...
Abstract 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 also includes cross-checked NOAA flare catalog that immediately facilitates prediction efforts. discuss methods used for data collection, cleaning pre-processing of the active region data, we further describe novel integration sampling methodology. covers 4,098 MVTS...
Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they the product of broad set physical processes corona out through extent heliosphere, and provide insight into particle acceleration transport that widely applicable in astrophysics. From operations perspective, SEP pose radiation hazard for aviation, electronics space, human space exploration, particular missions outside Earth's protective magnetosphere including to Moon Mars. Thus, it is critical...
We analytically study the damping of Alfvén mode oscillations in chromosphere and coronal loops. In partially ionized dominant process waves is due to collisions between ions neutrals. calculate time for a given frequency, propagating through model chromospheres various solar structures such as active region plage, quiet sun, penumbra umbra sunspots. For wave maximum always occurs at temperature minimum heights coldest structure(s), i.e., Energy dissipation ion-neutral with an energy flux...
We present a "head-to-tail" linkage model for the formation, evolution, and eruption of solar filaments. The magnetic field structure our is based on observation that filaments form exclusively in filament channels with no apparent connections above polarity inversion line. formation this configuration driven by flux convergence cancellation, which produces looplike segments half-turn. Filament like chirality may connect long quiescent Such are stabilized through footpoint anchoring until...
In this work we take advantage of eleven different sunspot group, sunspot, and active region databases to characterize the area flux distributions photospheric magnetic structures. We find that, when taken separately, are better fitted by (as has been reported previously in literature). However, that all our can be reconciled simple application a proportionality constant, reality, sampling parts composite distribution. This distribution is made up linear combination Weibull log-normal --...
view Abstract Citations (96) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Magnetic Fields in Quiescent Prominences van Ballegooijen, A. ; Martens, P. C. H. The origin of the axial fields high-latitude quiescent prominences is considered. fact that almost all obey same hemisphere-dependent rule strongly suggests solar differential rotation plays an important role producing fields. However, observations are inconsistent with hypothesis...
view Abstract Citations (86) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Generation of Proton Beams in Two-Ribbon Flares Martens, P. C. H. It is shown that, the current sheet at top arcade postflare loops a two-ribbon solar flare, particle beams are generated by direct electric-field acceleration. acceleration process completely collisionless and limited only gyromotion along component magnetic field perpendicular to sheet. This...
The emergence of tilted bipolar active regions (ARs) and the dispersal their flux, mediated via processes such as diffusion, differential rotation, meridional circulation, is believed to be responsible for reversal Sun's polar field. This process (commonly known Babcock–Leighton mechanism) usually modeled a near-surface, spatially distributed α-effect in kinematic mean-field dynamo models. However, this formulation leads relationship between field strength flow speed which opposite that...
We present a fast method for reconstructing differential emission measures (DEMs) using solar coronal data. The consists of fast, simple regularized inversion in conjunction with an iteration scheme removal residual negative measure. On average, it computes over 1000 DEMs s−1 sample active region observed by the Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatory, and achieves reduced chi-squared order unity no all but few test cases. high performance this is especially relevant...
"Moss" is the name given to low-lying (~3000 km), hot (~1 MK) solar coronal plasma that has been observed recently by Transition Region and Coronal Explorer (TRACE). This paper investigates two hypotheses regarding nature of moss: (1) emission from small, million degree loops; (2) legs 3-10 loops. We update radiative loss curve, using most recent results for abundances, use an analytical loop model find first hypothesis requires a filling factor close unity reproduce measure, while second in...
The turbulent magnetic diffusivity in the solar convection zone is one of most poorly constrained ingredients mean-field dynamo models. This lack constraint has previously led to controversy regarding appropriate set parameters, as different assumptions on value lead radically cycle predictions. Typically, community uses double step profiles characterized by low values bulk zone. However, these are not consistent with theoretical estimates based mixing-length theory -- which suggest much...
Abstract The activity of stars such as the Sun varies over timescales ranging from very short to long—stellar and planetary evolutionary timescales. Experience our solar system indicates that short-term, transient events stellar flares coronal mass ejections create hazardous space environmental conditions impact Earth-orbiting satellites atmospheres. Extreme superflares may play a role in atmospheric loss unsuitable for life. Slower, long-term evolutions Sun-like millennia billions years...
This work explores the impacts of magnetogram projection effects on machine learning-based solar flare forecasting models. Utilizing a methodology proposed by Falconer et al. (2016), we correct for present in Georgia State University's Space Weather Analytics Solar Flares (SWAN-SF) benchmark data set. We then train and run support vector classifier corrected uncorrected data, comparing differences performance. Additionally, provide insight into several other methodologies that mitigate...
Abstract This work explores the impacts of magnetogram projection effects on machine-learning-based solar flare forecasting models. Utilizing a methodology proposed by D. A. Falconer et al., we correct for present in Georgia State University’s Space Weather Analytics Solar Flares benchmark data set. We then train and test support vector machine classifier corrected uncorrected data, comparing differences performance. Additionally, provide insight into several other methodologies that...
We analyze the determination of coronal line-of-sight temperatures with technique narrowband filter ratios that is currently employed for data obtained Transition Region and Coronal Explorer EUV Imaging Telescope on board Solar Heliospheric Observatory. demonstrate simple fact observed differential emission measure curves in loops have a broad plateau everywhere along length loop leads to finding isothermal different each pair filters. show none thus correctly describe state plasma, which...
Magnetohydrodynamic dynamos operating in stellar interiors produce the diverse range of magnetic activity observed solar-like stars. Sophisticated dynamo models including realistic physics convection zone flows and flux tube dynamics have been built for Sun, which appropriate observations exist to constrain such models. Nevertheless, significant differences that invoke, most important being nature location α-effect whether it is spatially segregated from Ω-effect. Spatial segregation these...
view Abstract Citations (68) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Neutral Beams in Two-Ribbon Flares and the Geomagnetic Tail Martens, P. C. H. ; Young, A. The current sheet created wake of an erupting filament during a two-ribbon flare is studied. A comparison with geomagnetic tail shows that physics these systems very similar, therefore existence super Dreicer fields generation netural beams traveling down postflare loops small...
An essential ingredient in kinematic dynamo models of the solar cycle is internal velocity field within simulation domain—the convection zone (SCZ). In last decade or so, helioseismology has revolutionized our understanding this field. particular, differential rotation Sun now fairly well constrained by helioseismic observations almost throughout SCZ. Helioseismology also gives us some information about depth dependence meridional circulation near-surface layers Sun. The typical inputs used...
This paper introduces a new public benchmark dataset of solar image data from the Solar Dynamics Observatory (SDO) mission. is first release, which contains over 15,000 images and nearly 24,000 events, spanning six months 2012. It combines region-based event labels automated detection modules, ten pre-computed parameters for each cell grid-based segmentation full resolution images, lower version further analysis visualization. Together, these components serve as standardized, ready-to-use,...