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The nonpotentiality of coronae of solar active regions, the dynamics of the surface magnetic field, and the potential for large flares  

Karel Schrijver   Submitted: 2016-02-26 08:52

Flares and eruptions from solar active regions are associated with atmospheric electrical currents accompanying distortions of the coronal field away from a lowest-energy potential state. In order to better understand the origin of these currents and their role in M- and X-class flares, I review all active-region observations made with SDO/HMI and SDO/AIA from 2010/05 through 2014/10 within approximately 40 degrees from disk center. I select the roughly 4% of all regions that display a distinctly nonpotential coronal configuration in loops with a length comparable to the scale of the active region, and all that emit GOES X-class flares. The data for 41 regions confirm, with a single exception, that strong-field, high-gradient polarity inversion lines (SHILs) created during emergence of magnetic flux into, and related displacement within, pre-existing active regions are associated with X-class flares. Obvious nonpotentiality in the active region-scale loops occurs in 6 of 10 selected regions with X-class flares, all with relatively long SHILs along their primary polarity inversion line, or with a long internal filament there. Nonpotentiality can exist in active regions well past the flux-emergence phase, often with reduced or absent flaring. I conclude that the dynamics of the flux involved in the compact SHILs is of preeminent importance for the large-flare potential of active regions within the next day, but that their associated currents may not reveal themselves in active region-scale nonpotentiality. In contrast, active region-scale nonpotentiality, which can persist for many days, may inform us about the eruption potential other than those from SHILs which is almost never associated with X-class flaring.

Authors: C.J. Schrijver
Projects: SDO-AIA,SDO-HMI

Publication Status: Astrophysical Journal, in press.
Last Modified: 2016-02-29 10:55
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A Statistical Study of Distant Consequences of Large Solar Energetic Events  

Karel Schrijver   Submitted: 2015-09-18 10:05

Large solar flares and eruptions may influence remote regions through perturbations in the outer-atmospheric magnetic field, leading to causally related events outside of the primary or triggering eruptions that are referred to as ``sympathetic events''. We quantify the occurrence of sympathetic events using the full-disk observations by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory associated with all flares of GOES class M5 or larger from 01 May 2010 through 31 December 2014. Using a superposed-epoch analysis, we find an increase in the rate of flares, filament eruptions, and substantial sprays and surges more than 20 degrees away from the primary flares within the first four hours at a significance of 1.8 standard deviations. We also find that the rate of distant events drops by two standard deviations, or a factor of 1.2, when comparing intervals between 4 hours and 24 hours before and after the start times of the primary large flares. We discuss the evidence for the concluding hypothesis that the gradual evolution leading to the large flare and the impulsive release of the energy in that flare both contribute to the destabilization of magnetic configurations in distant active regions and quiet-Sun areas. These effects appear to leave distant regions, in an ensemble sense, in a more stable state, so that fewer energetic events happen for at least a day following large energetic events.

Authors: C.J. Schrijver, P.A. Higgins
Projects: SDO-AIA

Publication Status: Solar Physics, in press
Last Modified: 2015-09-23 13:30
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Assessing the impact of space weather on the electric power grid based on insurance claims for industrial electrical equipment  

Karel Schrijver   Submitted: 2014-06-09 18:15

Geomagnetically induced currents are known to induce disturbances in the electric power grid. Here, we perform a statistical analysis of 11,242 insurance claims from 2000 through 2010 for equipment losses and related business interruptions in North-American commercial organizations that are associated with damage to, or malfunction of, electrical and electronic equipment. We find that claims rates are elevated on days with elevated geomagnetic activity by approximately 20% for the top 5%, and by about 10% for the top third of most active days ranked by daily maximum variability of the geomagnetic field. When focusing on the claims explicitly attributed to electrical surges (amounting to more than half the total sample), we find that the dependence of claims rates on geomagnetic activity mirrors that of major disturbances in the U.S. high-voltage electric power grid. The claims statistics thus reveal that large-scale geomagnetic variability couples into the low-voltage power distribution network and that related power-quality variations can cause malfunctions and failures in electrical and electronic devices that, in turn, lead to an estimated 500 claims per average year within North America. We discuss the possible magnitude of the full economic impact associated with quality variations in electrical power associated with space weather.

Authors: C.J. Schrijver, R. Dobbins, W. Murtagh, S.M. Petrinec
Projects: None

Publication Status: Space Weather Journal, in press
Last Modified: 2014-06-10 10:08
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Space weather from explosions on the Sun: how bad could it be?  

Karel Schrijver   Submitted: 2014-06-09 18:12

How does one find out how severe extreme space weather can be? In this concise report we review the recent scientific literature on that topic, combining terrestrial, lunar, and stellar data. We find that solar flares, energetic particle storms, and geomagnetic disturbances can all be more intense than modern technology has experienced: flares could be hundreds of times more energetic, particle storms a few times more intense, and geomagnetic storms may exceed the strongest on record by a moderate factor. This publication summarizes the significant progress that has been made recently on establishing the statistics of the worst space weather, and that there is more data available that can be used to improve upon that.

Authors: C.J. Schrijver, J. Beer
Projects: None

Publication Status: EOS, in press, for June, 17 issue
Last Modified: 2014-06-10 10:09
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Disturbances in the U.S. electric grid associated with geomagnetic activity  

Karel Schrijver   Submitted: 2013-05-07 09:38

Large solar explosions are responsible for space weather that can impact technological infrastructure on and around Earth. Here, we apply a retrospective cohort exposure analysis to quantify the impacts of geomagnetic activity on the U.S. electric power grid for the period from 1992 through 2010. We find, with more than 3 sigma significance, that approximately 4% of the disturbances in the U.S. power grid reported to the U.S. Department of Energy are attributable to strong geomagnetic activity and its associated geomagnetically induced currents.

Authors: C.J. Schrijver and S.D. Mitchell
Projects: Other

Publication Status: Journal of Space Weather and Space Climate, 2013, in press
Last Modified: 2013-05-08 11:22
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Pathways of large-scale magnetic couplings between coronal events  

Karel Schrijver   Submitted: 2013-05-03 11:28

The high-cadence, comprehensive view of the solar corona by SDO/AIA shows many events that are widely separated in space while occurring close together in time. In some cases, sets of coronal events are evidently causally related, while in many other instances indirect evidence can be found. We present case studies to highlight a variety of coupling processes involved in coronal events. We find that physical linkages between events do occur, but concur with earlier studies that these couplings appear to be crucial to understanding the initiation of major eruptive or explosive phenomena relatively infrequently. We note that the post-eruption reconfiguration time scale of the large-scale corona, estimated from the EUV afterglow, is on average longer than the mean time between CMEs, so that many CMEs originate from a corona that is still adjusting from a previous event. We argue that the coronal field is intrinsically global: current systems build up over days to months, the relaxation after eruptions continues over many hours, and evolving connections easily span much of a hemisphere. This needs to be reflected in our modeling of the connections from the solar surface into the heliosphere to properly model the solar wind, its perturbations, and the generation and propagation of solar energetic particles. However, the large-scale field cannot be constructed reliably by currently available observational resources. We assess the potential of high-quality observations from beyond Earth's perspective and advanced global modeling to understand the couplings between coronal events in the context of CMEs and solar energetic particle events.

Authors: C.J. Schrijver, A.M. Title, A.R. Yeates and M.L. DeRosa
Projects: GOES X-rays ,SDO-AIA,SDO-HMI,STEREO

Publication Status: ApJSS, in press
Last Modified: 2013-05-03 13:15
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The 2011/02/15 X2 flare, ribbons, coronal wave, and mass ejection: interpreting the 3-d views from SDO and STEREO guided by MHD flux-rope modeling  

Karel Schrijver   Submitted: 2011-06-13 13:27

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.


Authors: C.J. Schrijver, G. Aulanier, A.M. Title, E. Pariat, C. Delannee
Projects: SDO-AIA,STEREO

Publication Status: ApJ, in press
Last Modified: 2011-06-14 19:51
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Long-range magnetic couplings between solar flares and coronal mass ejections observed by SDO and STEREO  

Karel Schrijver   Submitted: 2011-01-18 18:08

The combination of SDO and STEREO observations enable us to view much of the solar surface and atmosphere simultaneously and continuously. These near-global observations often show near-synchronous long-distance interactions between magnetic domains that exhibit flares, eruptions, and frequent minor forms of activity. Here, we analyze a series of flares, filament eruptions, coronal mass ejections, and related events which occurred on 2010/08/01-02. These events extend over a full hemisphere of the Sun, only two-thirds of which is visible from the Earth's perspective. The combination of coronal observations and global field modeling reveals the many connections between these events by magnetic field lines, particularly those at topological divides. We find that all events of substantial coronal activity, including those where flares and eruptions initiate, are connected by a system of separatrices, separators, and quasi-separatrix layers, with little activity within the deep interiors of domains of connectivity. We conclude that for this sequence of events the evolution of field on the hemisphere invisible from Earth's perspective is essential to the evolution, and possibly even to the initiation, of the flares and eruptions over an area that spans at least 180 degrees in longitude. Our findings emphasize that the search for the factors that play a role in the initiation and evolution of eruptive and explosive phenomena, sought after for improved space-weather forecasting, requires knowledge of much, if not all, of the solar surface field.

Authors: C.J. Schrijver and A.M. Title
Projects: SDO-AIA,SDO-HMI,STEREO

Publication Status: Journal of Geophysical Research (Space Physics), in press
Last Modified: 2011-01-19 08:46
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Solar energetic events, the solar-stellar connection, and statistics of extreme space weather  

Karel Schrijver   Submitted: 2010-12-13 08:00

Observations of the Sun and of Sun-like stars provide access to different aspects of stellar magnetic activity that, when combined, help us piece together a more comprehensive picture than can be achieved from only the solar or the stellar perspective. Where the Sun provides us with decent spatial resolution of, e.g., magnetic bipoles and the overlying dynamic, hot atmosphere, the ensemble of stars enables us to see rare events on at least some occasions. Where the Sun shows us how flux emergence, dispersal, and disappearance occur in the complex mix of polarities on the surface, only stellar observations can show us the activity of the ancient or future Sun. In this review, I focus on a comparison of statistical properties, from bipolar-region emergence to flare energies, and from heliospheric events to solar energetic particle impacts on Earth. In doing so, I point out some intriguing correspondences as well as areas where our knowledge falls short of reaching unambiguous conclusions on, for example, the most extreme space-weather events that we can expect from the present-day Sun. The difficulties of interpreting stellar coronal light curves in terms of energetic events are illustrated with some examples provided by the SDO, STEREO, and GOES spacecraft.

Authors: C.J. Schrijver
Projects: None

Publication Status: In press for the proceedings of the 16th workshop on Cool Stars, Stellar Systems, and the Sun
Last Modified: 2010-12-14 10:02
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Magnetic field topology and the thermal structure of the corona over solar active regions  

Karel Schrijver   Submitted: 2010-06-25 15:51

Solar extreme-ultraviolet images of quiescent active-region coronae are char- acterized by ensembles of bright 1 - 2 MK loops that fan out from select loca- tions. We investigate the conditions associated with the formation of these per- sistent, relatively cool loop fans within and surrounding the otherwise 3 - 5 MK coronal environment by combining extreme-ultraviolet (EUV) observations of ac- tive regions made with the Transition Region and Coronal Explorer (TRACE) with global source-surface potential-field models based on the full-sphere pho- tospheric field from the assimilation of magnetograms that are obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in the selected active regions with largely potential field configurations these fans are associated with (quasi-)separatrix layers (QSLs) within the strong-field regions of magnetic plage. Based on the empirical evidence, we argue that persistent active-region cool loop fans are primarily related to the pronounced change in connectivity across a QSL to widely separated clusters of magnetic flux, and confirm earlier work that sug- gested that neither a change in loop length nor in base field strengths across such topological features are of prime importance to the formation of the cool loop fans. We discuss the hypothesis that a change in the distribution of coronal heating with height may be involved in the phenomenon of relatively cool coronal loop fans in quiescent active regions.

Authors: Carolus J. Schrijver, Marc L. DeRosa, and Alan M. Title
Projects: TRACE

Publication Status: Astrophysical Journal, in press
Last Modified: 2010-06-28 09:15
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Eruptions from solar ephemeral regions as an extension of the size distribution of coronal mass ejections  

Karel Schrijver   Submitted: 2009-12-04 18:16

Observations of the quiet solar corona in the 171A (~1MK) passband of the Transition Region and Coronal Explorer (TRACE) often show disruptions of the coronal part of small-scale ephemeral bipolar regions that resemble the phenomena associated with coronal mass ejections on much larger scales: ephemeral regions exhibit flare-like brightenings, rapidly rising filaments carrying absorbing material at chromospheric temperatures, or the temporary dimming of the surrounding corona. I analyze all available TRACE observing sequences between 1998/04/01 and 2009/09/30 with full-resolution 171A image sequences spanning a day or more within 500 arcsec of disk center, observing essentially quiet Sun with good exposures and relatively low background. Ten such data sets are identified between 2000 and 2008, spanning 570h of observing with a total of 17133 exposures. Eighty small-scale coronal eruptions are identified. Their size distribution forms a smooth extension of the distribution of angular widths of coronal mass ejections, suggesting that the eruption frequency for bipolar magnetic regions is essentially scale free over at least two orders of magnitude, from eruptions near the arcsecond resolution limit of TRACE to the largest coronal mass ejections observed in the inner heliosphere. This scale range may be associated with the properties of the nested set of ranges of connectivity in the magnetic field, in which increasingly large and energetic events can reach higher and higher into the corona until the heliosphere is reached.

Authors: Carolus J. Schrijver
Projects: TRACE

Publication Status: In press for Astrophysical Journal
Last Modified: 2009-12-07 10:36
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Driving major solar flares and eruptions: a review  

Karel Schrijver   Submitted: 2008-11-05 10:56

This review focuses on the processes that energize and trigger major solar flares and flux-rope destabilizations. Numerical modeling of specific solar regions is hampered by uncertain coronal-field reconstructions and by poorly understood magnetic reconnection; these limitations result in uncertain estimates of field topology, energy, and helicity. The primary advances in understanding field destabilizations therefore come from the combination of generic numerical experiments with interpretation of sets of observations. These suggest a critical role for the emergence of twisted flux ropes into pre-existing strong field for many, if not all, of the active regions that produce M- or X-class flares. The flux and internal twist of the emerging ropes appear to play as important a role in determining whether an eruption will develop predominantly as flare, confined eruption, or CME, as do the properties of the embedding field. Based on reviewed literature, I outline a scenario for major flares and eruptions that combines flux-rope emergence, mass draining, near-surface reconnection, and the interaction with the surrounding field. Whether deterministic forecasting is in principle possible remains to be seen: to date no reliable such forecasts can be made. Large-sample studies based on long-duration, comprehensive observations of active regions from their emergence through their flaring phase are needed to help us better understand these complex phenomena.

Authors: C.J. Schrijver
Projects: None

Publication Status: in press for Advances in Space Research
Last Modified: 2008-11-05 13:40
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The Global Solar Magnetic Field Through a Full Sunspot Cycle: Observations and Model Results  

Karel Schrijver   Submitted: 2008-06-19 17:16

Based on 11 years of SOHO/MDI observations from the cycle minimum in 1997 to the next minimum around 2008, we compare observed and modeled axial dipole moments to better understand the large-scale transport properties of magnetic flux in the solar photosphere. The absolute value of the axial dipole moment in 2008 is less than half that in the corresponding cycle-minimum phase in early 1997, both as measured from synoptic maps and as computed from an assimilation model based only on magnetogram data equatorward of 60 degrees in latitude. This is incompatible with the statistical fluctuations expected from flux-dispersal modeling developed in earlier work at the level of 7-10 sigma. We show how this decreased axial dipole moment can result from an increased strength of the diverging meridional flow near the Equator, which more effectively separates the two hemispheres for dispersing magnetic flux. Based on the combination of this work with earlier long-term simulations of the solar surface field, we conclude that the flux-transport properties across the solar cycle have changed from preceding cycles to the most recent one. A plausible candidate for such a change is an increase of the gradient of the meridional-flow pattern near the Equator so that the two hemispheres are more effectively separated. The required profile as a function of latitude is consistent with helioseismic and cross-correlation measurements made over past decade.

Authors: C.J. Schrijver and Y. Liu
Projects: SoHO-MDI

Publication Status: Solar Physics, in press.
Last Modified: 2008-09-23 20:59
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Subject will be restored when possible  

Karel Schrijver   Submitted: 2007-12-03 09:28

We compare a variety of nonlinear force-free field (NLFFF) extrapolation algorithms, including optimization, magneto-frictional, and Grad-Rubin-like codes, applied to a solar-like reference model. The model used to test the algorithms includes realistic photospheric Lorentz forces and a complex field including a weakly twisted, right helical flux bundle. The codes were applied to both forced ``photospheric'' and more force-free ``chromospheric'' vector magnetic field boundary data derived from the model. When applied to the chromospheric boundary data, the codes are able to recover the presence of the flux bundle and the field's free energy, though some details of the field connectivity are lost. When the codes are applied to the forced photospheric boundary data, the reference model field is not well recovered, indicating that the combination of Lorentz forces and small spatial scale structure at the photosphere severely impact the extrapolation of the field. Preprocessing of the forced photospheric boundary does improve the extrapolations considerably for the layers above the chromosphere, but the extrapolations are sensitive to the details of the numerical codes and neither the field connectivity nor the free magnetic energy in the full volume are well recovered. The magnetic virial theorem gives a rapid measure of the total magnetic energy without extrapolation, though, like the NLFFF codes, it is sensitive to the Lorentz forces in the coronal volume. Both the magnetic virial theorem and the Wiegelmann extrapolation, when applied to the preprocessed photospheric boundary, give a magnetic energy which is nearly equivalent to the value derived from the chromospheric boundary, but both underestimate the free energy above the photosphere by at least a factor of two. We discuss the interpretation of the preprocessed field in this context. When applying the NLFFF codes to solar data, the problems associated with Lorentz forces present in the low solar atmosphere must be recognized: the various codes will not necessarily converge to the correct, or even the same, solution.

Authors: T.R. Metcalf, M.L. DeRosa, C.J. Schrijver, G. Barnes, A.A. van Ballegooijen, T. Wiegelmann, M.S. Wheatland, G. Valori, and J.M. McTiernan
Projects: None

Publication Status: Solar Physics, in press.
Last Modified: 2007-12-03 14:51
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Subject will be restored when possible  

Karel Schrijver   Submitted: 2007-11-30 15:20

Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of pre-existing atmospheric magnetic flux subject to surface plasma flows, or whether these currents are associated with the emergence of flux from within the solar convective zone. We address this problem by applying state-of-the-art nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA Active Region 10930 around the time of a powerful X3.4 flare. We compute 14 NLFFF models with 4 different codes and a variety of boundary conditions. We find that the model fields differ markedly in geometry, energy content, and force-freeness. We discuss the relative merits of these models in a general critique of present abilities to model the coronal magnetic field based on surface vector field measurements. For our application in particular, we find a fair agreement of the best-fit model field with the observed coronal configuration, and argue (1) that strong electrical currents emerge together with magnetic flux preceding the flare, (2) that these currents are carried in an ensemble of thin strands, (3) that the global pattern of these currents and of field lines are compatible with a large-scale twisted flux rope topology, and (4) that the sim 1032,erg change in energy associated with the coronal electrical currents suffices to power the flare and its associated coronal mass ejection.

Authors: C.J. Schrijver, M.L. DeRosa, T. Metcalf, G. Barnes, B. Lites, T. Tarbell, J. McTiernan, G. Valori, T. Wiegelmann, M.S. Wheatland, T. Amari, G. Aulanier, P. Demoulin, M. Fuhrmann, K. Kusano, S. Regnier, and J.K. Thalmann
Projects: Hinode

Publication Status: ApJ (in press)
Last Modified: 2007-12-01 08:29
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Subject will be restored when possible  

Karel Schrijver   Submitted: 2007-10-08 10:57

We examine the early phases of two near-limb filament destabilizations involved in coronal mass ejections on 16 June and 27 July 2005, using high-resolution, high-cadence observations made with the Transition Region and Coronal Explorer (TRACE), complemented by coronagraphic observations by Mauna Loa and the SOlar and Heliospheric Observatory (SOHO). The filaments' heights above the solar limb in their rapid-acceleration phases are best characterized by a height dependence h(t)~ t^m with m near, or slightly above, 3 for both events. Such profiles are incompatible with published results for breakout, MHD-instability, and catastrophe models. We show numerical simulations of the torus instability that approximate this height evolution in case a substantial initial velocity perturbation is applied to the developing instability. We argue that the sensitivity of magnetic instabilities to initial and boundary conditions requires higher fidelity modeling of all proposed mechanisms if observations of rise profiles are to be used to differentiate between them. The observations show no significant delays between the motions of the filament and of overlying loops: the filaments seem to move as part of the overall coronal field until several minutes after the onset of the rapid-acceleration phase.

Authors: C.J. Schrijver, C. Elmore, B. Kliem, T. Torok, and A.M. Title
Projects: TRACE

Publication Status: ApJ (in press)
Last Modified: 2007-10-09 08:53
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A characteristic magnetic field pattern associated with all major solar flares and its use in flare forecasting  

Karel Schrijver   Submitted: 2007-01-05 15:29

Solar flares result from some electromagnetic instability that occurs within regions of relatively strong magnetic field in the Sun's atmosphere. The processes that enable and trigger these flares remain topics of intense study and debate. I analyze observations of 289 X- and M-class flares and over 2,500 active-region magnetograms to discover (1) that large flares, without exception, are associated with the rise from within the Sun of intense magnetic fibrils with pronounced high-gradient polarity separation lines, while (2) the free energy that emerges with these fibrils is converted into flare energy in a broad spectrum of flare magnitudes that may well be selected at random from a power-law distribution up to a maximum value. This maximum is proportional to the total unsigned flux R within ~15 Mm of strong-field, high-gradient polarity-separation lines which are a characteristic appearance of electrical currents emerging through the photosphere. Measurement of R is readily automated, and R can therefore be used effectively for flare forecasting. The probability for major flares to occur within 24 hr of the measurement of R approaches unity for active regions with the highest values of R around 2x1021 Mx. For regions with R<1019 Mx, no M- or X-class flares occur within a day.

Authors: Carolus J. Schrijver
Projects: TRACE

Publication Status: ApJL, in press
Last Modified: 2007-01-08 10:00
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Gamma-rays and the evolving, compact structures of the 2003/10/28 X17 flare  

Karel Schrijver   Submitted: 2006-06-05 08:55

The X17 flare on 2003/10/28 was observed by high-resolution imaging or spectroscopic instruments on CORONAS, GOES, INTEGRAL, RHESSI, SOHO, and TRACE. These spacecraft observed the temporal evolution of the gamma-ray positron-annihilation and nuclear de-excitation line spectra, imaged the hard-X-ray bremsstrahlung and EUV and UV emission, and measured the surface magnetic field and subphotospheric pressure perturbations. In the usual pattern, the onset of the flare is dominated by particle acceleration and interaction, and by the filling of coronal magnetic structures with hot plasma. The associated positron annihilation signatures early in the impulsive phase from 11:06 UT to 11:16 UT have a line-broadening temperature characteristic of a few hundred thousand Kelvin. The most intense precipitation sites within the extended flare ribbons are very compact, with diameters of less than 1,400 km and a 195A TRACE intensity that can exceed 7,500x the quiescent active-region value. These regions appear to move at speeds of up to 60 km s-1. The associated rapidly-evolving, compact perturbations of the photosphere below these sites excite acoustic pulses that propagate into the solar interior. Less intense precipitation sites persist typically for several minutes behind the advancing flare ribbons. After ~1 ksec, the flare enters a second phase, dominated by coronal plasma cooling and downflows, and by annihilation line radiation characteristic of a photospheric environment. We point out 1) that these detailed observations underscore that flare models need to explicitly incorporate the multitude of successively excited eftwo{environments whose evolving signals differ at least in their temporal offsets and energy budgets if not also in the exciting particle populations and penetration depths}, and 2) that the spectral signatures of the positron annihilation do not fit conventional model assumptions.

Authors: C.J. Schrijver, H.S. Hudson, R.J. Murphy, G.H. Share, and T.D. Tarbell
Projects: TRACE

Publication Status: Accepted for publication in the Astrophysical Journal
Last Modified: 2006-06-06 14:29
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Abstracts by Author
The nonpotentiality of coronae of solar active regions, the dynamics of the surface magnetic field, and the potential for large flares
A Statistical Study of Distant Consequences of Large Solar Energetic Events
Assessing the impact of space weather on the electric power grid based on insurance claims for industrial electrical equipment
Space weather from explosions on the Sun: how bad could it be?
Disturbances in the U.S. electric grid associated with geomagnetic activity
Pathways of large-scale magnetic couplings between coronal events
The 2011/02/15 X2 flare, ribbons, coronal wave, and mass ejection: interpreting the 3-d views from SDO and STEREO guided by MHD flux-rope modeling
Long-range magnetic couplings between solar flares and coronal mass ejections observed by SDO and STEREO
Solar energetic events, the solar-stellar connection, and statistics of extreme space weather
Magnetic field topology and the thermal structure of the corona over solar active regions
Eruptions from solar ephemeral regions as an extension of the size distribution of coronal mass ejections
Driving major solar flares and eruptions: a review
The Global Solar Magnetic Field Through a Full Sunspot Cycle: Observations and Model Results
Subject will be restored when possible
Subject will be restored when possible
Subject will be restored when possible
A characteristic magnetic field pattern associated with all major solar flares and its use in flare forecasting
Gamma-rays and the evolving, compact structures of the 2003/10/28 X17 flare

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