Author name code: welsch ADS astronomy entries on 2022-09-14 author:Welsch, Brian ------------------------------------------------------------------------ Title: Reconstruction of Photospheric Velocity Fields from Highly Corrupted Data Authors: Rempel, Erico L.; Chertovskih, Roman; Davletshina, Kamilla R.; Silva, Suzana S. A.; Welsch, Brian T.; Chian, Abraham C. -L. Bibcode: 2022ApJ...933....2R Altcode: 2022arXiv220509846R The analysis of the photospheric velocity field is essential for understanding plasma turbulence in the solar surface, which may be responsible for driving processes such as magnetic reconnection, flares, wave propagation, particle acceleration, and coronal heating. Currently, the only available methods to estimate velocities at the solar photosphere transverse to an observer's line of sight infer flows from differences in image structure in successive observations. Due to data noise, algorithms such as local correlation tracking may lead to a vector field with wide gaps where no velocity vectors are provided. In this paper, a novel method for image inpainting of highly corrupted data is proposed and applied to the restoration of horizontal velocity fields in the solar photosphere. The restored velocity field preserves all the vector field components present in the original field. The method shows robustness when applied to both simulated and observational data. Title: Invited Review: Short-term Variability with the Observations from the Helioseismic and Magnetic Imager (HMI) Onboard the Solar Dynamics Observatory (SDO): Insights into Flare Magnetism Authors: Kazachenko, Maria D.; Albelo-Corchado, Marcel F.; Tamburri, Cole A.; Welsch, Brian T. Bibcode: 2022SoPh..297...59K Altcode: Continuous vector magnetic-field measurements by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) allow us to study magnetic-field properties of many flares. Here, we review new observational aspects of flare magnetism described using SDO data, including statistical properties of magnetic-reconnection fluxes and their rates, magnetic fluxes of flare dimmings, and magnetic-field changes during flares. We summarize how these results, along with statistical studies of coronal mass ejections (CMEs), have improved our understanding of flares and the flare/CME feedback relationship. Finally, we highlight future directions to improve the current state of understanding of solar-flare magnetism using observations. Title: Toward Improved Understanding of Magnetic Fields Participating in Solar Flares: Statistical Analysis of Magnetic Fields within Flare Ribbons Authors: Kazachenko, Maria D.; Lynch, Benjamin J.; Savcheva, Antonia; Sun, Xudong; Welsch, Brian T. Bibcode: 2022ApJ...926...56K Altcode: 2021arXiv211106048K Violent solar flares and coronal mass ejections (CMEs) are magnetic phenomena. However, how magnetic fields reconnecting in the flare differ from nonflaring magnetic fields remains unclear owing to the lack of studies of the flare magnetic properties. Here we present a first statistical study of flaring (highlighted by flare ribbons) vector magnetic fields in the photosphere. Our systematic approach allows us to describe the key physical properties of solar flare magnetism, including distributions of magnetic flux, magnetic shear, vertical current, and net current over flaring versus nonflaring parts of the active region (AR), and compare these with flare/CME properties. Our analysis suggests that while flares are guided by the physical properties that scale with AR size, like the total amount of magnetic flux that participates in the reconnection process and the total current (extensive properties), CMEs are guided by mean properties, like the fraction of the AR magnetic flux that participates (intensive property), with little dependence on the amount of shear at the polarity inversion line (PIL) or the net current. We find that the nonneutralized current is proportional to the amount of shear at the PIL, providing direct evidence that net vertical currents are formed as a result of any mechanism that could generate magnetic shear along the PIL. We also find that eruptive events tend to have smaller PIL fluxes and larger magnetic shears than confined events. Our analysis provides a reference for more realistic solar and stellar flare models. The database is available online and can be used for future quantitative studies of flare magnetism. Title: Data-driven, time-dependent modeling of pre-eruptive coronal magnetic field configuration at the periphery of NOAA AR 11726 Authors: Lumme, E.; Pomoell, J.; Price, D. J.; Kilpua, E. K. J.; Kazachenko, M. D.; Fisher, G. H.; Welsch, B. T. Bibcode: 2022A&A...658A.200L Altcode: Context. Data-driven, time-dependent magnetofrictional modeling has proved to be an efficient tool for studying the pre-eruptive build-up of energy for solar eruptions, and sometimes even the ejection of coronal flux ropes during eruptions. However, previous modeling works have illustrated the sensitivity of the results on the data-driven boundary condition, as well as the difficulty in modeling the ejections with proper time scales.
Aims: We aim to study the pre- and post-eruptive evolution of a weak coronal mass ejection producing eruption at the periphery of isolated NOAA active region (AR) 11726 using a data-driven, time-dependent magnetofrictional simulation, and aim to illustrate the strengths and weaknesses of our simulation approach.
Methods: We used state-of-the-art data processing and electric field inversion methods to provide the data-driven boundary condition for the simulation. We analyzed the field-line evolution, magnetic connectivity, twist, as well as the energy and helicity budgets in the simulation to study the pre- and post-eruptive magnetic field evolution of the observed eruption from AR11726.
Results: We find the simulation to produce a pre-eruptive flux rope system consistent with several features in the extreme ultraviolet and X-ray observations of the eruption, but the simulation largely fails to reproduce the ejection of the flux rope. We find the flux rope formation to be likely driven by the photospheric vorticity at one of the footpoints, although reconnection at a coronal null-point may also feed poloidal flux to the flux rope. The accurate determination of the non-inductive (curl-free) component of the photospheric electric field boundary condition is found to be essential for producing the flux rope in the simulation.
Conclusions: Our results illustrate the applicability of the data-driven, time-dependent magnetofrictional simulations in modeling the pre-eruptive evolution and formation process of a flux rope system, but they indicate that the modeling output becomes problematic for the post-eruptive times. For the studied event, the flux rope also constituted only a small part of the related active region.

Movies are available at https://www.aanda.org Title: Toward Improved Understanding of Magnetic Fields Participating in Solar Flares: Statistical Analysis of Magnetic Field within Flare Ribbons Authors: Kazachenko, Maria; Lynch, Benjamin; Savcheva, Antonia; Welsch, Brian Bibcode: 2021AGUFMSH45B2378K Altcode: Flares and coronal mass ejections are manifestations of magnetic evolution in the solar corona in which magnetic reconnection is believed to play key roles. While the properties of underlying, photospheric line-of-sight magnetic fields of active regions (ARs) as a whole have been analyzed in detail, properties of vector magnetic fields that participate in the reconnection process, highlighted by the flare ribbons, have not been described. Here we present a statistical analysis of vector magnetic field properties in 40 ARs associated with 33 eruptive and 7 confined flares, of GOES class C9.0 and greater. For every event in the database, we use a HMI/SDO vector magnetogram, and AIA 1600A images to calculate various properties of the photospheric vector magnetic field within the AR, flare ribbons and the polarity inversion line (PIL) areas: magnetic flux, reconnection flux fraction, magnetic shear, vertical electric current and current neutralization. We find that while the peak X-ray flux has a strong correlation with ribbon reconnection flux, it has only moderate correlation with the magnetic shear within ribbon- and PIL- areas and the degree of current neutralization. We find a new linear relationship between the amount of non-neutralized current within the AR (or ribbon) and the amount of shear at PIL. This scaling is consistent with earlier simulations and case studies, of net currents being formed as a result of any mechanism that could generate magnetic shear along PIL: flux emergence, twisting or shearing motions. Finally, we find that the CME speed has a much stronger correlation with the reconnection flux fraction than with any other active region property. We also find that for a fixed peak X-ray flux, eruptive events tend to have smaller PIL fluxes and larger magnetic shears than confined events. To summarize, our observational analysis, supported by MHD ARMS and magnetofrictional simulations, suggests that flare peak X-ray fluxes and CME speeds are most strongly guided by the total amount of magnetic flux that participates in the reconnection process and the amount of the flux in the overlying field, than by the amount of PIL shear or AR net current. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Oscillations observed in umbra, plage, quiet-Sun and the polarity inversion line of active region 11158 using Helioseismic Magnetic Imager/Solar Dynamics Observatory data Authors: Norton, A. A.; Stutz, R. B.; Welsch, B. T. Bibcode: 2021RSPTA.37900175N Altcode: 2021arXiv210101349N Using data from the Helioseismic Magnetic Imager, we report on the amplitudes and phase relations of oscillations in quiet-Sun, plage, umbra and the polarity inversion line (PIL) of an active region NOAA#11158. We employ Fourier, wavelet and cross-correlation spectra analysis. Waves with 5 min periods are observed in umbra, PIL and plage with common phase values of φ(v, I) = π/2, φ(v, Blos) = -(π/2). In addition, φ(I, Blos) = π in plage are observed. These phase values are consistent with slow standing or fast standing surface sausage wave modes. The line width variations, and their phase relations with intensity and magnetic oscillations, show different values within the plage and PIL regions, which may offer a way to further differentiate wave mode mechanics. Significant Doppler velocity oscillations are present along the PIL, meaning that plasma motion is perpendicular to the magnetic field lines, a signature of Alvènic waves. A time-distance diagram along a section of the PIL shows Eastward propagating Doppler oscillations converting into magnetic oscillations; the propagation speeds range between 2 and 6 km s-1. Lastly, a 3 min wave is observed in select regions of the umbra in the magnetogram data.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Determine Coronal Magnetic Field Evolution Authors: Kazachenko, Maria; Abbett, Bill; Liu, Yang; Fisher, George; Welsch, Brian; Bercik, Dave; DeRosa, Marc; Cheung, Mark; Sun, Xudong; Hoeksema, J. Todd; Erkka Lumme, .; Hayashi, Keiji; Lynch, Benjamin Bibcode: 2021cosp...43E1785K Altcode: The Coronal Global Evolutionary Model (CGEM) provides data-driven simulations of the magnetic field in the solar corona to better understand the build-up of magnetic energy that leads to eruptive events. The CGEM project has developed six capabilities. CGEM modules (1) prepare time series of full-disk vector magnetic field observations to (2) derive the changing electric field in the solar photosphere over active-region scales. This local electric field is (3) incorporated into a surface flux transport model that reconstructs a global electric field that evolves magnetic flux in a consistent way. These electric fields drive a (4) 3D spherical magnetofrictional (SMF) model, either at high resolution over a restricted range of solid angles or at lower resolution over a global domain to determine the magnetic field and current density in the low corona. An SMF-generated initial field above an active region and the evolving electric field at the photosphere are used to drive (5) detailed magnetohydrodynamic (MHD) simulations of active regions in the low corona. SMF or MHD solutions are then used to compute emissivity proxies that can be compared with coronal observations. Finally, a lower-resolution SMF magnetic field is used to initialize (6) a global MHD model that is driven by an SMF electric field time series to simulate the outer corona and heliosphere, ultimately connecting Sun to Earth. As a demonstration, this report features results of CGEM applied to observations of the evolution of NOAA Active Region 11158 in 2011 February. Title: Extended, Kilogauss Bald Patches in the Super-Flaring Solar Active Region 12673 Authors: Sun, Xudong; Gibson, Sarah; Welsch, Brian; Titov, Viacheslav Bibcode: 2021cosp...43E1730S Altcode: Bald patch (BP) is a magnetic topological feature where U-shaped field lines turn tangent to the photosphere. When accompanied by shear, BPs suggest the existence of pre-eruption magnetic flux ropes (MFRs). Previous studies often found them in young solar active regions (ARs) with patchy flux emergence, or decaying ARs with weaker magnetic field. Here we report on a coherent, strong-field example observed in the super-flaring AR 12673. The central BP, located in a narrow delta_x000E_-spot penumbral lane, extended over 10 Mm with field strength above 2 kG. It formed over a period 10 hr, which featured fast Doppler downflow, gradual azimuth rotation, field strength reduction, and field gradient enhancement. It then rapidly disintegrated during a GOES X9 flare. Coronal field extrapolation reveals a low-lying, kilogauss MFR with over two turns of twist wrapped inside three intersecting BP separatrices (BPSs). The early-phase flare ribbons coincide with BPS foot prints. We discuss the BP formation mechanism such as flux cancellation, its stability condition, and its role in the eruption. Title: The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Determine Coronal Magnetic Field Evolution Authors: Hoeksema, J. Todd; Abbett, William P.; Bercik, David J.; Cheung, Mark C. M.; DeRosa, Marc L.; Fisher, George H.; Hayashi, Keiji; Kazachenko, Maria D.; Liu, Yang; Lumme, Erkka; Lynch, Benjamin J.; Sun, Xudong; Welsch, Brian T. Bibcode: 2020ApJS..250...28H Altcode: 2020arXiv200614579H The Coronal Global Evolutionary Model (CGEM) provides data-driven simulations of the magnetic field in the solar corona to better understand the build-up of magnetic energy that leads to eruptive events. The CGEM project has developed six capabilities. CGEM modules (1) prepare time series of full-disk vector magnetic field observations to (2) derive the changing electric field in the solar photosphere over active-region scales. This local electric field is (3) incorporated into a surface flux transport model that reconstructs a global electric field that evolves magnetic flux in a consistent way. These electric fields drive a (4) 3D spherical magnetofrictional (SMF) model, either at high resolution over a restricted range of solid angles or at lower resolution over a global domain to determine the magnetic field and current density in the low corona. An SMF-generated initial field above an active region and the evolving electric field at the photosphere are used to drive (5) detailed magnetohydrodynamic (MHD) simulations of active regions in the low corona. SMF or MHD solutions are then used to compute emissivity proxies that can be compared with coronal observations. Finally, a lower-resolution SMF magnetic field is used to initialize (6) a global MHD model that is driven by an SMF electric field time series to simulate the outer corona and heliosphere, ultimately connecting Sun to Earth. As a demonstration, this report features results of CGEM applied to observations of the evolution of NOAA Active Region 11158 in 2011 February. Title: The PDFI_SS Electric Field Inversion Software Authors: Fisher, George H.; Kazachenko, Maria D.; Welsch, Brian T.; Sun, Xudong; Lumme, Erkka; Bercik, David J.; DeRosa, Marc L.; Cheung, Mark C. M. Bibcode: 2020ApJS..248....2F Altcode: 2019arXiv191208301F We describe the PDFI_SS software library, which is designed to find the electric field at the Sun's photosphere from a sequence of vector magnetogram and Doppler velocity measurements and estimates of horizontal velocities obtained from local correlation tracking using the recently upgraded Fourier Local Correlation Tracking code. The library, a collection of FORTRAN subroutines, uses the "PDFI" technique described by Kazachenko et al., but modified for use in spherical, Plate Carrée geometry on a staggered grid. The domain over which solutions are found is a subset of the global spherical surface, defined by user-specified limits of colatitude and longitude. Our staggered grid approach, based on that of Yee, is more conservative and self-consistent compared to the centered, Cartesian grid used by Kazachenko et al. The library can be used to compute an end-to-end solution for electric fields from data taken by the HMI instrument aboard NASA's SDO mission. This capability has been incorporated into the HMI pipeline processing system operating at SDO's Joint Science Operations Center. The library is written in a general and modular way so that the calculations can be customized to modify or delete electric field contributions, or used with other data sets. Other applications include "nudging" numerical models of the solar atmosphere to facilitate assimilative simulations. The library includes an ability to compute "global" (whole-Sun) electric field solutions. The library also includes an ability to compute potential magnetic field solutions in spherical coordinates. This distribution includes a number of test programs that allow the user to test the software. Title: The PDFI_SS Electric Field Inversion Software Authors: Fisher, George H.; Kazachenko, Maria D.; Welsch, Brian T.; Lumme, Erkka Bibcode: 2020zndo...3711571F Altcode: This is a copy of the PDFI_SS electric field inversion software, as described in arXiv 1912.08301. Title: The FLCT local correlation tracking software Authors: Fisher, George H.; Welsch, Brian T. Bibcode: 2020zndo...3711569F Altcode: FLCT consists of a library of functions, written in C, for performing tasks associated with local correlation tracking, and the approximate inverse operation, the warping of an image by a two-dimensional displacement function. The library is written in such a way that it can be called easily from either C or Fortran. The software also includes source code for two standalone executables, flct and warp, which will perform the correlation tracking or warping by reading input files and then creating output files that can be read from other applications, such as IDL. Title: Statistical Analysis of Solar Flare Ribbon Properties Using Observations from Solar Dynamics Observatory Authors: Kazachenko, M.; Lynch, B. J.; Welsch, B. T.; Sun, X. Bibcode: 2019AGUFMSH12B..03K Altcode: We extend our RibbonDB database of >3000 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45 degrees from the disk center, from April 2010 until April 2019, observed by the Solar Dynamics Observatory (SDO). For every event in the database, we compare GOES X-ray and SDO/EVE flare properties with corresponding active-region and flare-ribbon properties, including cumulative reconnection flux and peak reconnection flux rate. We present the results and discuss what could be learnt from studying typical and outlier flares to deepen our understanding of solar flare physics. Title: Photospheric Flows & DKIST: Resolving Both Smaller Scales And Open Questions Authors: Welsch, Brian Bibcode: 2019AAS...23422602W Altcode: The technical aim of DKIST is to resolve dynamics on spatial scales not yet observed - an achievement that also promises to resolve many important science questions. For instance, the characteristics of photospheric velocity fields on currently unresolved scales - such as the strength of vorticity present, and the lifetimes of flow patterns - have substantial implications for theories chromospheric and coronal heating. Parker long ago hypothesized that the braiding of flux tubes by photospheric flows might play a role in the generation of current sheets above the photosphere, whose dissipation should lead to atmospheric heating. More recently, van Ballegooijen and collaborators have proposed that photospheric flows evolving on time scales shorter than the round-trip, photosphere-to-transition-region travel time for Alfven waves could lead to counter-propagating waves that should induce turbulence and subsequent dissipative heating. Using methods like local correlation tracking (LCT) and feature tracking to infer flows in rapid-cadence, high-resolution DKIST observations of magnetized regions of the lower solar atmosphere should enable testing these, and other, coronal heating models. Title: What is the role of flare ribbon structure on CME speeds? Authors: Welsch, Brian; Hencheck, Michael; Kazachenko, Maria D.; Ginsburg, David Bibcode: 2019AAS...23411201W Altcode: Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances, but remain poorly understood. Hence, efforts to characterize and predict their dynamics are ongoing. Many CMEs are associated with solar flares, and, in particular, flare ribbons, which are bright bands of strongly enhanced emission originating above magnetized areas of the photosphere. As a solar eruption progresses, these ribbons typically move across areas that contain fluxes of order 1021 Mx or more. The rate at which the ribbons sweep across photospheric flux is thought to correspond to the rate of coronal magnetic reconnection. Previous studies found significant correlations between CME speeds and the total amount of flux swept by flare ribbons. Here, we investigate relationships between CME speeds and spatial moments of their source-region photospheric magnetic fields and flare ribbons, including spatial moments of: (i) magnetic flux in the source region; (ii) signed and (iii) unsigned magnetic flux within ribbon areas; and (iv) binary maps ribbon areas. Our sample consists of N = 75 CMEs in the SOHO/LASCO CME catalog that were manually associated with flare ribbons identified in SDO/AIA data. Vector magnetograms obtained by SDO/HMI were used in our calculations of source-region magnetic properties. We confirm prior results that correlations between CME speeds and total magnetic fluxes swept by flare ribbons are statistically significant. We also find that spatial moments of ribbon magnetic fields are also significantly correlated with CME speeds. Title: Probing the Effect of Cadence on the Estimates of Photospheric Energy and Helicity Injections in Eruptive Active Region NOAA AR 11158 Authors: Lumme, E.; Kazachenko, M. D.; Fisher, G. H.; Welsch, B. T.; Pomoell, J.; Kilpua, E. K. J. Bibcode: 2019SoPh..294...84L Altcode: 2019arXiv190700367L We study how the input-data cadence affects the photospheric energy and helicity injection estimates in eruptive NOAA Active Region 11158. We sample the novel 2.25-minute vector magnetogram and Dopplergram data from the Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO) spacecraft to create input datasets of variable cadences ranging from 2.25 minutes to 24 hours. We employ state-of-the-art data processing, velocity, and electric-field inversion methods for deriving estimates of the energy and helicity injections from these datasets. We find that the electric-field inversion methods that reproduce the observed magnetic-field evolution through the use of Faraday's law are more stable against variable cadence: the PDFI (PTD-Doppler-FLCT-Ideal, where PTD refers to Poloidal-Toroidal Decomposition, and FLCT to Fourier Local Correlation Tracking) electric-field inversion method produces consistent injection estimates for cadences from 2.25 minutes up to two hours, implying that the photospheric processes acting on time scales below two hours contribute little to the injections, or that they are below the sensitivity of the input data and the PDFI method. On other hand, the electric-field estimate derived from the output of DAVE4VM (Differential Affine Velocity Estimator for Vector Magnetograms), which does not fulfill Faraday's law exactly, produces significant variations in the energy and helicity injection estimates in the 2.25 minutes - two hours cadence range. We also present a third, novel DAVE4VM-based electric-field estimate, which corrects the poor inductivity of the raw DAVE4VM estimate. This method is less sensitive to the changes of cadence, but it still faces significant issues for the lowest of considered cadences (≥ two hours). We find several potential problems in both PDFI- and DAVE4VM-based injection estimates and conclude that the quality of both should be surveyed further in controlled environments. Title: Flux Accretion and Coronal Mass Ejection Dynamics Authors: Welsch, Brian T. Bibcode: 2018SoPh..293..113W Altcode: 2017arXiv170109082W Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. Models of CME dynamics have been proposed that do not fully include the effects of magnetic reconnection on the forces driving the ejection. Both observations and numerical modeling, however, suggest that reconnection likely plays a major role in most, if not all, fast CMEs. Here, we theoretically investigate the accretion of magnetic flux onto a rising ejection by reconnection involving the ejection's background field. This reconnection alters the magnetic structure of the ejection and its environment, thereby modifying the forces acting upon the ejection, generically increasing its upward acceleration. The modified forces, in turn, can more strongly drive the reconnection. This feedback process acts, effectively, as an instability, which we refer to as a reconnective instability. Our analysis implies that CME models that neglect the effects of reconnection cannot accurately describe observed CME dynamics. Our ultimate aim is to understand changes in CME acceleration in terms of observable properties of magnetic reconnection, such as the amount of reconnected flux. This flux can be estimated from observations of flare ribbons and photospheric magnetic fields. Title: Using Photospheric Vector Magnetograms to Drive Coronal Field Models Authors: Welsch, Brian T.; CGEM Team Bibcode: 2018shin.confE..89W Altcode: Solar flares and coronal mass ejections (CMEs) are driven by the release of free magnetic energy stored in electric currents in the coronal magnetic field. Without photospheric forcing, the large-scale coronal field should, in principle, maintain a nearly steady equilibrium. Photospheric evolution must therefore play a central role in driving the corona to produce flares and CMEs. Consequently, observations of the photospheric vector magnetic field provide crucial inputs for understanding this Title: Flux Accretion and Coronal Mass Ejection Dynamics Authors: Welsch, Brian T. Bibcode: 2018shin.confE.190W Altcode: Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. Models of CME dynamics have been proposed that do not fully include the effects of magnetic reconnection on the forces driving the ejection. Both observations and numerical modeling, however, suggest that reconnection likely plays a major role in most, if not all, fast CMEs. Here, we theoretically investigate the accretion of magnetic flux onto a rising ejection by reconnection involving the ejection's background field. This reconnection alters the magnetic structure of the ejection and its environment, thereby modifying the forces acting upon the ejection, generically increasing its upward acceleration. The modified forces, in turn, can more strongly drive the reconnection. This feedback process acts, effectively, as an instability, which we refer to as a reconnective instability. Our analysis implies that CME models that neglect the effects of reconnection do not correctly describe observed CME dynamics. Our ultimate aim is to understand changes in CME acceleration in terms of observable properties of magnetic reconnection, such as the amount of reconnected flux, deduced from observations of flare ribbons and photospheric magnetic fields. Title: What are the Roles of Magnetic Field and Flare Ribbon Structure on CME Dynamics? Authors: Ginsburg, David E.; Welsch, Brian Bibcode: 2018tess.conf10420G Altcode: Disturbances in the near-Earth space environment - known as space weather events - can impact humanity's infrastructure. Understanding and predicting space weather, however, remains challenging. Because coronal mass ejections (CMEs) are the primary driver of severe space weather disturbances, much work revolves around the characterization and prediction of their dynamics. Some CMEs are associated with solar flares, and, in particular, "ribbons" of strongly enhanced emission near the base of the corona (the Sun's outer atmosphere). Previous work demonstrated a statistical relationship between CME speeds and the strengths of their source flares. It has been proposed that quadrupolar magnetic regions are more unstable to eruption than bipolar magnetic regions. Motivated by the idea that source regions' magnetic structure might influence eruption dynamics, we investigate relationships between CME speeds and properties of their source-region magnetic fields and flare ribbons, including spatial moments of: (i) the radial photospheric flux distribution; (ii) binary maps of the flare ribbons; and (iii) flux-weighted maps of the flare-ribbons. We first worked to associate flare ribbons in an existing database with CMEs, by comparing the times and locations of flares as determined by the NOAA/GOES flare catalog with CME data taken from the SOHO/LASCO CME catalog. The N = 76 flare/CME associations that we made comprise our dataset. Magnetic field maps of CME source regions, obtained with the HMI satellite, were used to calculate the spatial moments that we analyze. We have calculated correlations between these moments and two measures of CME speeds, as well as single- and multivariable regressions of CME speeds as functions of these moments. Title: Flux Accretion and Coronal Mass Ejection Dynamics Authors: Welsch, Brian T. Bibcode: 2018tess.conf10414W Altcode: Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. Models of CME dynamics have been proposed that do not fully include the effects of magnetic reconnection on the forces driving the ejection. Both observations and numerical modeling, however, suggest that reconnection likely plays a major role in most, if not all, fast CMEs. Here, we theoretically investigate the accretion of magnetic flux onto a rising ejection by reconnection involving the ejection's background field. This reconnection alters the magnetic structure of the ejection and its environment, thereby modifying the forces acting upon the ejection, generically increasing its upward acceleration. The modified forces, in turn, can more strongly drive the reconnection. This feedback process acts, effectively, as an instability, which we refer to as a reconnective instability. Our analysis implies that CME models that neglect the effects of reconnection cannot accurately describe observed CME dynamics. Our ultimate aim is to understand changes in CME acceleration in terms of observable properties of magnetic reconnection, such as the amount of reconnected flux, deduced from observations of flare ribbons and photospheric magnetic fields. <hr> Title: A Database of Flare Ribbon Properties From Solar Dynamics Observatory: Reconnection Flux Authors: Kazachenko, Maria D.; Welsch, Brian; Lynch, Benjamin J.; Sun, Xudong Bibcode: 2017SPD....4810824K Altcode: We present a database of 3137 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45 degrees from the disk center, from April 2010 until April 2016, observed by the Solar Dynamics Observatory. For every event in the database, we compare the GOES peak X-ray flux with corresponding active-region and flare-ribbon properties. We find that while the peak X-ray flux is not correlated with the AR unsigned magnetic flux, it is strongly correlated with the flare ribbon reconnection flux, flare ribbon area, and the fraction of active region flux that undergoes reconnection. We find the relationship between the peak X-ray flux and the flare ribbon reconnection flux to be I_{X,peak} ~ \Phi_{ribbon}^{1.3} for flares >M1 and I_{X,peak} ~ \Phi_{ribbon}^{1.5} over the entire flare set (>C1). This scaling law is consistent with earlier hydrodynamic simulations of impulsively heated flare loops. Using the flare reconnection flux as a proxy for the total released flare energy E, we find that the occurrence frequency of flare energies follows a power-law dependence: dN/dE ~ E^{-1.6} for E within 10^{31} to 10^{33} erg, consistent with earlier studies of solar and stellar flares. This database is available online and can be used for future quantitative studies of flares. Title: A Database of Flare Ribbon Properties from the Solar Dynamics Observatory. I. Reconnection Flux Authors: Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian T.; Sun, Xudong Bibcode: 2017ApJ...845...49K Altcode: 2017arXiv170405097K We present a database of 3137 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45° from the central meridian, from 2010 April until 2016 April, observed by the Solar Dynamics Observatory. For every event in the database, we compare the GOES peak X-ray flux with the corresponding active region and flare ribbon properties. We find that while the peak X-ray flux is not correlated with the active region unsigned magnetic flux, it is strongly correlated with the flare ribbon reconnection flux, flare ribbon area, and the fraction of active region flux that undergoes reconnection. We find the relationship between the peak X-ray flux and the flare ribbon reconnection flux to be {I}{{X},{peak}}\propto {{{Φ }}}{ribbon}1.5. This scaling law is consistent with earlier hydrodynamic simulations of impulsively heated flare loops. Using the flare reconnection flux as a proxy for the total released flare energy E, we find that the occurrence frequency of flare energies follows a power-law dependence: {dN}/{dE}\propto {E}-1.6 for {10}31< E< {10}33 {erg}, consistent with earlier studies of solar and stellar flares. The database is available online and can be used for future quantitative studies of flares. Title: Flux Accretion and Coronal Mass Ejection Dynamics Authors: Welsch, Brian Bibcode: 2017SPD....4820607W Altcode: Coronal mass ejections (CMEs) are the primary drivers of severe space weather disturbances in the heliosphere. The equations of ideal magnetohydrodynamics (MHD) have been used to model the onset and, in some cases, the subsequent acceleration of ejections. Both observations and numerical modeling, however, suggest that magnetic reconnection likely plays a major role in most, if not all, fast CMEs. Here, we theoretically investigate the dynamical effects of accretion of magnetic flux onto a rising ejection by reconnection involving the ejection's background field. This reconnection alters the magnetic structure of the ejection and its environment, thereby modifying forces acting during the eruption, generically leading to faster acceleration of the CME. Our ultimate aim is to characterize changes in CME acceleration in terms of observable properties of magnetic reconnection, such as the amount of reconnected flux, deduced from observations of flare ribbons and photospheric magnetic fields. Title: A Database of Flare Ribbon Properties From Solar Dynamics Observatory: Reconnection Flux Authors: Kazachenko, Maria D.; Welsch, Brian T.; Lynch, Benjamin; Sun, Xudong Bibcode: 2017shin.confE..35K Altcode: We present a database of 3137 solar flare ribbon events corresponding to every flare of GOES class C1.0 and greater within 45 degrees from the disk center, from April 2010 until April 2016, observed by the Solar Dynamics Observatory. For every event in the database, we compare the GOES peak X-ray flux with corresponding active-region and flare-ribbon properties. We find that while the peak X-ray flux is not correlated with the AR unsigned magnetic flux, it is strongly correlated with the flare ribbon reconnection flux, flare ribbon area, and the fraction of active region flux that undergoes reconnection. We find the relationship between the peak X-ray flux and the flare ribbon reconnection flux to be I_{X,peak} Φ_{ribbon}^{1.3} for flares >M1 and I_{X,peak} Φ_{ribbon}^{1.5} over the entire flare set (>C1). This scaling law is consistent with earlier hydrodynamic simulations of impulsively heated flare loops. Using the flare reconnection flux as a proxy for the total released flare energy E, we find that the occurrence frequency of flare energies follows a power-law dependence: dN/dE E^{-1.6} for E within 10^{31} to 10^{33} erg, consistent with earlier studies of solar and stellar flares. This database is available online and can be used for future quantitative studies of flares. Title: Advanced Materials Characterization of P-Rich and P-Poor Regions Within Single-Crystal Olivine Authors: Hammer, J. E.; Ishii, H. A.; Bradley, J. P.; Shea, T.; Welsch, B.; Hellebrand, E. Bibcode: 2017LPI....48.2375H Altcode: We are studying how P is incorporated in olivine, by resolving differences in the abundance and geometry of defects within P-rich and P-poor olivine. Title: Magmatic Cooling History of Troctolite 76535 Constrained by Diffusion Modeling of Olivine and Plagioclase Compositional Zonation Authors: Hammer, J. E.; Shea, T.; Taylor, G. J.; Hellebrand, E.; Welsch, B. Bibcode: 2017LPI....48.1274H Altcode: Rapid initial crystallization of 76535 is suggested by diffusion modeling of olivine compositional zonation. Title: The Roles of Reconnected Flux and Overlying Fields in CME Speeds Authors: Deng, Minda; Welsch, Brian T. Bibcode: 2017SoPh..292...17D Altcode: 2015arXiv150402905D Researchers have reported i) correlations of coronal mass ejection (CME) speeds and the total photospheric magnetic flux swept out by flare ribbons in flare-associated eruptive events, and, separately, ii) correlations of CME speeds and more rapid decay, with height, of magnetic fields in potential-field coronal models above eruption sites. Here, we compare the roles of both ribbon fluxes and the decay rates of overlying fields in a set of 16 eruptive events. We confirm previous results that higher CME speeds are associated with both higher ribbon fluxes and more rapidly decaying overlying fields. We find the association with ribbon fluxes to be weaker than a previous report, but stronger than the dependence on the decay rate of overlying fields. Since the photospheric ribbon flux is thought to approximate the amount of coronal magnetic flux reconnected during the event, the correlation of speeds with ribbon fluxes suggests that reconnection plays some role in accelerating CMEs. One possibility is that reconnected fields that wrap around the rising ejection produce an increased outward hoop force, thereby increasing CME acceleration. The correlation of CME speeds with more rapidly decaying overlying fields might be caused by greater downward magnetic tension in stronger overlying fields, which could act as a source of drag on rising ejections. Title: A Database of Flare Ribbons Observed By Solar Dynamics Observatory Authors: Kazachenko, M.; Lynch, B. J.; Welsch, B. T. Bibcode: 2016AGUFMSH34A..03K Altcode: Flare ribbons are emission structures observed during flares in transition-region and in chromospheric. They typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to automatically compile a complete dataset of flare-ribbon events. Here we present a dataset of both flare ribbon positions and reconnection fluxes, as a function of time, for all C-class flares within 45 degrees of disk center observed by the SDO. Title: The Circulation and Closure of Electric Currents in the Solar Atmosphere Authors: Kazachenko, M.; Fisher, G. H.; Bercik, D. J.; Welsch, B. T.; Lynch, B. J. Bibcode: 2016AGUFMSH31B2579K Altcode: How much information about vertical and horizontal currents flowing inthe solar atmosphere can we learn from a single vector magnetogramtaken at the photosphere? It is well-known that one can determine theradial current density by taking the curl of the magnetic fieldcomponents parallel to an idealised photospheric surface. Here, weinvestigate the additional information that can be learned abouthorizontal currents flowing in the atmosphere above the photosphere.In particular, we study the radially integrated horizontal currentdistribution, expressed as a surface current density. In ourformalism, this surface-current density is projected onto thephotospheric surface, even though it represents currents flowing atall heights in the atmosphere. Horizontal currents reflect twosources: (1) currents flowing around radial magnetic distributions;and (2) horizontal currents that originate as radial currents at thephotosphere, become horizontal above it, and return to the photosphereagain as radial currents. Our aim is to derive two-dimensional``maps'' of how currents flow through the solar atmosphere that can bederived from vector magnetic field measurements at a single height. Title: Deriving Potential Coronal Magnetic Fields from Vector Magnetograms Authors: Welsch, Brian T.; Fisher, George H. Bibcode: 2016SoPh..291.1681W Altcode: 2016SoPh..tmp..120W; 2015arXiv150308754W The minimum-energy configuration for the magnetic field above the solar photosphere is curl-free (hence, by Ampère's law, also current-free), so can be represented as the gradient of a scalar potential. Since magnetic fields are divergence free, this scalar potential obeys Laplace's equation, given an appropriate boundary condition (BC). With measurements of the full magnetic vector at the photosphere, it is possible to employ either Neumann or Dirichlet BCs there. Historically, the Neumann BC was used with available line-of-sight magnetic field measurements, which approximate the radial field needed for the Neumann BC. Since each BC fully determines the 3D vector magnetic field, either choice will, in general, be inconsistent with some aspect of the observed field on the boundary, due to the presence of both currents and noise in the observed field. We present a method to combine solutions from both Dirichlet and Neumann BCs to determine a hybrid, "least-squares" potential field, which minimizes the integrated square of the residual between the potential and actual fields. We also explore weighting the residuals in the fit by spatially uniform measurement uncertainties. This has advantages both in not overfitting the radial field used for the Neumann BC, and in maximizing consistency with the observations. We demonstrate our methods with SDO/HMI vector magnetic field observations of active region 11158, and find that residual discrepancies between the observed and potential fields are significant, and they are consistent with nonzero horizontal photospheric currents. We also analyze potential fields for two other active regions observed with two different vector magnetographs, and find that hybrid-potential fields have significantly less energy than the Neumann fields in every case - by more than 1032erg in some cases. This has major implications for estimates of free magnetic energy in coronal field models, e.g., non-linear force-free field extrapolations. Title: Using Two-Ribbon Flare Data Set to Constrain Flare Properties Authors: Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian T. Bibcode: 2016shin.confE.118K Altcode: Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 407 events of both flare ribbon positions and fluxes, as a function of time, for all C8.-class and greater flares within 45 degrees of disk center observed by SDO from April 2010 till April 2016. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably Title: A Potential Field Model for Spherical Sub-domains Authors: Fisher, George H.; Bercik, David; Welsch, Brian; Kazachenko, Maria D.; CGEM Team Bibcode: 2016SPD....47.0308F Altcode: Potential field models are used widely in Solar Physics to estimate coronal magnetic field geometry and connectivity, to provide lower limits on magnetic energies, and to provide initial configurations for time-dependent models of magnetic fields in the solar atmosphere. Potential field models in a spherical geometry can be global, covering the entire Sun, or confined to localized sub-volumes of the sphere. Here, we focus on the latter case.We describe an efficient potential field model for localized spherical sub-volumes (wedges consisting of upper and lower limits of radius, co-latitude, and longitude), employing a finite-difference approach for the solution. The solution is derived in terms of a "poloidal" potential, which can then be used to find either the scalar potential or the vector potential for the magnetic field (if desired), as well as all three magnetic field components. The magnetic field components are computed on the faces of spherical voxels, and the finite difference grid is consistent with the well-known "Yee" grid. The inner spherical boundary is defined by radial magnetic field measurements, and at the outer radius a source-surface boundary condition is imposed.Potential field solutions on active region scales, at full HMI resolution, and with the source surface located a solar radius above the photosphere, can be obtained on a laptop computer in just a few minutes. The three-dimensional finite difference equations are solved using NCAR's FISHPACK elliptic equation solver.The potential field model was developed by the Coronal Global Evolutionary Model (CGEM) project, funded by the NASA and NSF Strategic Capabilities program. The potential field model described here was motivated by CGEM's need for such a model. The model will be released as open-source code when the model details are published. Title: Revisiting Ribbon Fluxes and CME Speeds Authors: Welsch, Brian; Kazachenko, Maria D.; Hencheck, Michael Bibcode: 2016SPD....47.0338W Altcode: The dynamics of coronal mass ejections (CMEs) remain poorly understood. A previous study found that the final speeds of CMEs were strongly correlated with the amount of photospheric magnetic flux swept out by flare ribbons. The latter quantity, which we refer to as the ribbon flux, is thought to be directly related to the amount of coronal magnetic flux that reconnects during an eruption. The prior study, however, analyzed flare ribbons associated with a small sample (N=13) of relatively fast CMEs (all > 600 km/s, mean speed > 1300 km/s). With the launch of the Solar Dynamics Observatory (SDO) in 2010, automated co-registration of ribbon images observed in UV by its Atmospheric Imaging Assembly (AIA) with line-of-sight magnetograms observed by its Helioseismic and Magnetic Imager (HMI) enabled compilation of a relatively large database of ribbon fluxes. Here, we characterize relationships between ribbon fluxes and the speeds (and other properties) of manually-associated CMEs in a sample of several dozen events. Title: Using Two-Ribbon Flare Observations and MHD Simulations to Constrain Flare Properties Authors: Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian Bibcode: 2016SPD....47.0612K Altcode: Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 363 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from June 2010 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes, reconnection flux rates and vertical currents with the properties from MHD simulations. Title: Active Region Emergence and Remote Flares Authors: Fu, Yixing; Welsch, Brian T. Bibcode: 2016SoPh..291..383F Altcode: 2016SoPh..tmp...13F; 2015arXiv150406633F We study the effect of new emerging solar active regions on the large-scale magnetic environment of existing regions. We first present a theoretical approach to quantify the "interaction energy" between new and pre-existing regions as the difference between i) the summed magnetic energies of their individual potential fields and ii) the energy of their superposed potential fields. We expect that this interaction energy can, depending upon the relative arrangements of newly emerged and pre-existing magnetic flux, indicate the existence of "topological" free magnetic energy in the global coronal field that is independent of any "internal" free magnetic energy due to coronal electric currents flowing within the newly emerged and pre-existing flux systems. We then examine the interaction energy in two well-studied cases of flux emergence, but find that the predicted energetic perturbation is relatively small compared to energies released in large solar flares. Next, we present an observational study of the influence of the emergence of new active regions on flare statistics in pre-existing active regions, using NOAA's Solar Region Summary and GOES flare databases. As part of an effort to precisely determine the emergence time of active regions in a large event sample, we find that emergence in about half of these regions exhibits a two-stage behavior, with an initial gradual phase followed by a more rapid phase. Regarding flaring, we find that the emergence of new regions is associated with a significant increase in the occurrence rate of X- and M-class flares in pre-existing regions. This effect tends to be more significant when pre-existing and new emerging active regions are closer. Given the relative weakness of the interaction energy, this effect suggests that perturbations in the large-scale magnetic field, such as topology changes invoked in the "breakout" model of coronal mass ejections, might play a significant role in the occurrence of some flares. Title: Data Set of Flare-Ribbon Reconnected Magnetic Fluxes: A Critical Tool for Understanding Solar Flares and Eruptions Authors: Kazachenko, M.; Lynch, B. J.; Welsch, B. T. Bibcode: 2015AGUFMSH23D..08K Altcode: Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 141 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from January 2013 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes and reconnection flux rates, with the properties from theoretical models. Title: Photospheric Electric Fields and Energy Fluxes in the Eruptive Active Region NOAA 11158 Authors: Kazachenko, Maria D.; Fisher, George H.; Welsch, Brian T.; Liu, Yang; Sun, Xudong Bibcode: 2015ApJ...811...16K Altcode: 2015arXiv150505974K How much electromagnetic energy crosses the photosphere in evolving solar active regions (ARs)? With the advent of high-cadence vector magnetic field observations, addressing this fundamental question has become tractable. In this paper, we apply the “PTD-Doppler-FLCT-Ideal” (PDFI) electric field inversion technique of Kazachenko et al. to a 6-day vector magnetogram and Doppler velocity sequence from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory to find the electric field and Poynting flux evolution in NOAA 11158, which produced an X2.2 flare early on 2011 February 15. We find photospheric electric fields ranging up to 2 V cm-1. The Poynting fluxes range from [-0.6 to 2.3] × {10}10 {erg} cm-2 s-1, mostly positive, with the largest contribution to the energy budget in the range of [{10}9-{10}10] erg cm-2 s-1. Integrating the instantaneous energy flux over space and time, we find that the total magnetic energy accumulated above the photosphere from the initial emergence to the moment before the X2.2 flare to be E=10.6× {10}32 {erg}, which is partitioned as 2.0×1032erg and 8.6× {10}32 {erg}, respectively, between free and potential energies. Those estimates are consistent with estimates from preflare nonlinear force-free field extrapolations and the Minimum Current Corona estimates, in spite of our very different approach. This study of photospheric electric fields demonstrates the potential of the PDFI approach for estimating Poynting fluxes and opens the door to more quantitative studies of the solar photosphere and more realistic data-driven simulations of coronal magnetic field evolution. Title: A Data Set of Flare-Ribbon Magnetic Fluxes: A Critical Tool for Understanding Solar Flares & Eruptions Authors: Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian T. Bibcode: 2015shin.confE..13K Altcode: Flare Ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux -- the amount of unsigned photospheric magnetic flux swept out by flare ribbons -- is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 141 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from January 2013 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably Title: The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Model the Buildup of Free Magnetic Energy in the Solar Corona Authors: Fisher, G. H.; Abbett, W. P.; Bercik, D. J.; Kazachenko, M. D.; Lynch, B. J.; Welsch, B. T.; Hoeksema, J. T.; Hayashi, K.; Liu, Y.; Norton, A. A.; Dalda, A. Sainz; Sun, X.; DeRosa, M. L.; Cheung, M. C. M. Bibcode: 2015SpWea..13..369F Altcode: 2015arXiv150506018F The most violent space weather events (eruptive solar flares and coronal mass ejections) are driven by the release of free magnetic energy stored in the solar corona. Energy can build up on timescales of hours to days, and then may be suddenly released in the form of a magnetic eruption, which then propagates through interplanetary space, possibly impacting the Earth's space environment. Can we use the observed evolution of the magnetic and velocity fields in the solar photosphere to model the evolution of the overlying solar coronal field, including the storage and release of magnetic energy in such eruptions? The objective of CGEM, the Coronal Global Evolutionary Model, funded by the NASA/NSF Space Weather Modeling program, is to develop and evaluate such a model for the evolution of the coronal magnetic field. The evolving coronal magnetic field can then be used as a starting point for magnetohydrodynamic (MHD) models of the corona, which can then be used to drive models of heliospheric evolution and predictions of magnetic field and plasma density conditions at 1AU. Title: Photospheric Magnetic Energy Input and the Atmospheric Response Authors: Welsch, Brian T. Bibcode: 2015TESS....111105W Altcode: How are the chromospheres and coronae of the Sun and solar-like stars heated to much higher temperatures than their photospheres? Understanding atmospheric heating has been a major, unsolved problem in solar and stellar astrophysics for many decades now. Convective motions at the photosphere acting on the footpoints of coronal magnetic fields are presumed to inject magnetic energy into the Sun's atmosphere, where it is later released as heat. To investigate this hypothesis, the upward flux of magnetic energy across the photosphere --- quantified by the Poynting flux --- can be estimated by combining photospheric vector magnetic field measurements with horizontal photospheric velocities inferred by local correlation tracking (LCT) applied to magnetogram sequences. Recently published estimates of the net upward Poynting flux were roughly consistent with the expected energy demand required for chromospheric and coronal heating. But how are variations in magnetic energy injected across the photosphere related to variations in emission in the chromosphere, transition region, and corona? Comparisons between the estimated upward transport of magnetic energy and the atmospheric response are an essential step toward a comprehensive understanding of the physical processes that drive chromospheric and coronal heating. To address this issue, we have begun efforts to compare variations in chromospheric, transition region, and coronal emission observed by IRIS and SDO/AIA with estimates of the photospheric Poynting flux derived from sequential Hinode/SOT SpectroPolarimeter and Narrowband Filter Imager magnetograms of plage magnetic fields in active regions. Here, we will present initial results of our comparisons. This work is supported by NASA under contract NNG09FA40C (IRIS). Title: The Coronal Global Evolutionary Model (CGEM): Toward Routine, Time-Dependent, Data-Driven Modeling of the Active Corona Authors: Welsch, Brian T.; Cheung, Mark CM; Fisher, George H.; Kazachenko, Maria D.; Sun, Xudong Bibcode: 2015TESS....131106W Altcode: The Coronal Global Evolutionary Model (CGEM) is a model for the evolution of the magnetic field in the solar corona, driven using photospheric vector magnetic field and Doppler measurements by the HMI instrument on NASA's Solar Dynamics Observatory. Over days-long time scales, the coronal magnetic field configuration is determined quasi-statically using magnetofrictional relaxation. For a configuration that becomes unstable and erupts or undergoes rapid evolution, we can use the magnetofrictional configuration as the initial state for MHD simulations. The model will be run in both global configurations, covering the entire Sun, and local configurations, designed to model the evolution of the corona above active regions. The model uses spherical coordinates to realistically treat the large-scale coronal geometry. The CGEM project also includes the dissemination of other information derivable from HMI magnetogram data, such as (i) vertical and horizontal Lorentz forces computed over active region domains, to facilitate easier comparisons of flare/CME behavior and observed changes of the photospheric magnetic field, and (ii) estimates of the photospheric electric field and Poynting flux. We describe progress that we have made in development of both the coronal model and its input data, and discuss magnetic evolution in (i) the well-studied NOAA AR 11158 around the time of the 2011 February 15 X2.2 flare, and (ii) AR 11944 around the time of the 2014 January 7 X1.2 flare. Title: The photospheric Poynting flux and coronal heating Authors: Welsch, Brian T. Bibcode: 2015PASJ...67...18W Altcode: 2015PASJ..tmp..156W; 2014arXiv1402.4794W Some models of coronal heating suppose that convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we investigate this idea by estimating the upward transport of magnetic energy-the vertical Poynting flux, Sz-across the photosphere in a plage region. To do so, we combine the following: (i) estimates of photospheric horizontal velocities, vh, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are (i) strong enough to be measured with relatively small uncertainties, (ii) not so strong that convection is heavily suppressed (as within umbrae), and (iii) unipolar, so Sz in plage is not influenced by mixed-polarity processes (e.g., flux emergence) unrelated to heating in stable, active-region fields. In this plage region, we found that the average Sz varied in space, but was positive (upward) and sufficient to explain coronal heating, with values near (5 ± 1) × 107 erg cm-2 s-1. We find the energy input per unit magnetic flux to be on the order of 105 erg s-1 Mx-1. A comparison of intensity in a Ca II image co-registered with one plage magnetogram shows stronger spatial correlations with both total field strength and unsigned vertical field, |Bz|, than either Sz or horizontal flux density, Bh. The observed Ca II brightness enhancement, however, probably contains a strong contribution from a near-photosphere hot-wall effect, which is unrelated to heating in the solar atmosphere. Title: On the Relationship between Solar Magnetic Forces and CME Momenta Authors: Li, Yan; Lynch, Ben; Sun, Xudong; Welsch, Brian T.; Bercik, David J.; Fisher, George H. Bibcode: 2015TESS....130219L Altcode: Free magnetic energy is the energy source of solar flares and CMEs. At the initiation of a CME, the free magnetic energy converts to kinetic energy and few other types of energy. Observable magnetic field sudden changes have been found at the onset of flares. The Lorentz force around the onset of a flare have been formulated in recent studies and can be estimated using photospheric vector magnetic field data. It is proposed that outward Lorentz force impulses could be related to CME momenta. We analyze about 30 CMEs and their source region magnetic fields. The best vector magnetic field data are observed for active regions near the center of the solar disk. We first select CMEs that appear to be halo or partial halo CMEs in the LASCO images, and then we use STEREO SECCHI COR2 white light images to estimate CME mass and speed. We then estimate the Lorentz forces in the source active regions at the flare onset using SDO HMI photosheric vector magnetic field data. We report our studies and describe our analyses.This study is under the support of NSF grants. Title: Sign Singularity and Flares in Solar Active Region NOAA 11158 Authors: Sorriso-Valvo, L.; De Vita, G.; Kazachenko, M. D.; Krucker, S.; Primavera, L.; Servidio, S.; Vecchio, A.; Welsch, B. T.; Fisher, G. H.; Lepreti, F.; Carbone, V. Bibcode: 2015ApJ...801...36S Altcode: 2015arXiv150104279S Solar Active Region NOAA 11158 has hosted a number of strong flares, including one X2.2 event. The complexity of current density and current helicity are studied through cancellation analysis of their sign-singular measure, which features power-law scaling. Spectral analysis is also performed, revealing the presence of two separate scaling ranges with different spectral index. The time evolution of parameters is discussed. Sudden changes of the cancellation exponents at the time of large flares and the presence of correlation with Extreme-Ultra-Violet and X-ray flux suggest that eruption of large flares can be linked to the small-scale properties of the current structures. Title: The relationship between CME momenta and magnetic forces Authors: Li, Y.; Lynch, B. J.; Welsch, B. T.; Bercik, D. J. Bibcode: 2014AGUFMSH43B4206L Altcode: Free magnetic energy is the energy source of solar flares and CMEs. At theinitiation of a CME, the free magnetic energy converts to kinetic energy and few other types of energy. Observable magnetic field sudden changes havebeen found at the onset of flares. The Lorentz force around the onset of a flare have been formulated in recent studies and can be estimatedusing photospheric vector magnetic field data. It is proposed that outward Lorentz force impulses could be related to CME momenta. We analyze about 30 CMEs and their source region magnetic fields.The best vector magnetic field data are observed for active regions nearthe center of the solar disk. We first select CMEs that appear to be haloor partial halo CMEs in the LASCO images, and then we use STEREO SECCHI COR2white light images to estimate CME mass and speed. We then estimatethe Lorentz forces in the source active regions at the flare onset using SDO HMI photosheric vector magnetic field data.We report our work in progress and describe our analyses. Title: The Photosheric Poynting Flux and Coronal Heating Authors: Welsch, B. T. Bibcode: 2014AGUFMSH31C..08W Altcode: Some models of coronal heating suppose that convective motions at thephotosphere shuffle the footpoints of coronal magnetic fields andthereby inject sufficient magnetic energy upward to account forobserved coronal and chromospheric energy losses in active regions.Using high-resolution observations of plage magnetic fields made withthe Solar Optical Telescope aboard the Hinode satellite, weinvestigate this idea by estimating the upward transport of magneticenergy --- the vertical Poynting flux, S_z --- across the photospherein a plage region. To do so, we combine: (i) estimates ofphotospheric horizontal velocities, v_h, determined by localcorrelation tracking applied to a sequence of line-of-sight magneticfield maps from the Narrowband Filter Imager, with (ii) a vectormagnetic field measurement from the SpectroPolarimeter. Plage fieldsare ideal observational targets for estimating energy injection byconvection, because they are: (i) strong enough to be measured withrelatively small uncertainties; (ii) not so strong that convection isheavily suppressed (as within umbrae); and (iii) unipolar, so S_z inplage is not influenced by mixed-polarity processes (e.g., fluxemergence) unrelated to heating in stable, active-region fields. Inthis plage region, we found that the average S_z varied in space, butwas positive (upward) and sufficient to explain coronal heating, withvalues near (5 +/- 1) x 107 erg / cm2 / s. We find the energy inputper unit magnetic flux to be on the order of 105 erg / s / Mx. Acomparison of intensity in a Ca II image co-registered with one plagemagnetogram shows stronger spatial correlations with both total fieldstrength and unsigned vertical field, |B_z|, than either S_z orhorizontal flux density, B_h. The observed Ca II brightnessenhancement, however, probably contains a strong contribution from anear-photosphere hot-wall effect, which is unrelated to heating in thesolar atmosphere. Title: Do New Solar Active Regions Trigger Flares in Existing Regions? Authors: Fu, Y.; Welsch, B. T. Bibcode: 2014AGUFMSH41B4133F Altcode: We study the effect of new emerging solar active regions on the large-scale magnetic environment of existing regions. We first present a theoretical approach to quantify the "interaction energy" between new and pre-existing regions by identifying the part of the magnetic potential field energy that couples the new and old flux systems. We then examine this energy in two well-studied cases of flux emergence, but find that the predicted energetic perturbation is very small compared to energies released in large solar flares. Next, we present an observational study of the influence of the emergence new active regions on flare statistics in pre-existing active regions. As part of an effort to precisely determine the emergence time of active regions in a large sample, we find that emergence in about half of these regions exhibits a two-stage behavior, with an initial gradual phase followed by a more rapid phase. Preliminary results regarding flaring suggest that newly emerging regions trigger a marginally significant increase in the occurrence rate of X- and M-class flares in pre-existing regions. Title: A Comprehensive Method of Estimating Electric Fields from Vector Magnetic Field and Doppler Measurements Authors: Kazachenko, Maria D.; Fisher, George H.; Welsch, Brian T. Bibcode: 2014ApJ...795...17K Altcode: 2014arXiv1404.4027K Photospheric electric fields, estimated from sequences of vector magnetic field and Doppler measurements, can be used to estimate the flux of magnetic energy (the Poynting flux) into the corona and as time-dependent boundary conditions for dynamic models of the coronal magnetic field. We have modified and extended an existing method to estimate photospheric electric fields that combines a poloidal-toroidal decomposition (PTD) of the evolving magnetic field vector with Doppler and horizontal plasma velocities. Our current, more comprehensive method, which we dub the "PTD-Doppler-FLCT Ideal" (PDFI) technique, can now incorporate Doppler velocities from non-normal viewing angles. It uses the FISHPACK software package to solve several two-dimensional Poisson equations, a faster and more robust approach than our previous implementations. Here, we describe systematic, quantitative tests of the accuracy and robustness of the PDFI technique using synthetic data from anelastic MHD (ANMHD) simulations, which have been used in similar tests in the past. We find that the PDFI method has less than 1% error in the total Poynting flux and a 10% error in the helicity flux rate at a normal viewing angle (θ = 0) and less than 25% and 10% errors, respectively, at large viewing angles (θ < 60°). We compare our results with other inversion methods at zero viewing angle and find that our method's estimates of the fluxes of magnetic energy and helicity are comparable to or more accurate than other methods. We also discuss the limitations of the PDFI method and its uncertainties. Title: Relationship between the photospheric Poynting flux and the active region luminosity Authors: Kazachenko, Maria D.; Canfield, Richard C.; Fisher, George H.; Hudson, Hugh S.; Welsch, Brian Bibcode: 2014AAS...22412349K Altcode: How does energy radiated by active regions compare with magnetic energy that propagates lower across the photosphere? This is a fundamental question for energy storage and release in active regions, yet it is presently poorly understood. In this work we quantify and compare both energy terms using SDO observations of the active region (AR) 11520. To quantify the magnetic energy crossing the photosphere, or the Poynting flux, we need to know both the magnetic field vector B and electric field vector E as well. Our current electric field inversion technique, PDFI, combines the Poloidal-Toroidal-Decomposition method with information from Doppler measurements, Fourier local correlation tracking (FLCT) results, and the ideal MHD constraint, to determine the electric field from vector magnetic field and Doppler data. We apply the PDFI method to a sequence of Helioseismic and Magnetic Imager (HMI/SDO) vector magnetogram data, to find the electric-field and hence the Poynting-flux evolution in AR 11520. We find that most of the magnetic energy in this AR is injected in the range of $10^7$ to $10^8$ $ergs/{cm^2 s}$, with the largest fluxes reaching $10^{10}$ $ergs/{cm^2 s}$. Integrating over the active region this yields a total energy of order $10^{28}$ ergs/s. To quantify the active region luminosity, we use EUV Variability Experiment (EVE) and Atmospheric Imaging Assembly (AIA) spectrally resolved observations. We find the active region luminosity of order $10^{28}$ ergs/s. We compare derived magnetic and radiated energy fluxes on different temporal and spatial scales and estimate their uncertainties. We also discuss the roles that potential/non-potential and emerging/shearing terms play in the total magnetic energy budget. Title: The Photospheric Poynting Flux and Coronal Heating Authors: Welsch, Brian Bibcode: 2014AAS...22410305W Altcode: Some models of coronal heating suppose that random (cf., coherent) convective motions at the photosphere shuffle the footpoints of coronal magnetic fields and thereby inject sufficient magnetic energy upward to account for observed coronal and chromospheric energy losses in active regions. Using high-resolution observations of plage magnetic fields made with the Solar Optical Telescope aboard the Hinode satellite, we observationally test this idea by estimating the upward transport of magnetic energy --- the vertical Poynting flux, S_z --- across the photosphere in a plage region. To do so, we combine: (i) estimates of photospheric horizontal velocities, v_h, determined by local correlation tracking applied to a sequence of line-of-sight magnetic field maps from the Narrowband Filter Imager, with (ii) a vector magnetic field measurement from the SpectroPolarimeter. Plage fields are ideal observational targets for estimating energy injection by convection, because they are: (i) strong enough to be measured with relatively small uncertainties; (ii) not so strong that convection is heavily suppressed (as within umbrae); and (iii) unipolar, so S_z in plage is not influenced by mixed-polarity processes (e.g., flux emergence) that cannot explain steady heating in stable, active-region fields. In this and a previously analyzed plage region, we found that the average S_z varied between the regions, but was positive (upward) and sufficient to explain coronal heating, with values near 2 x 10^7 erg/ cm^2/ s. We find the energy input per unit magnetic flux to be on the order of a few times 10^4 erg/ s/ Mx. A comparison of intensity in a Ca II image co-registered with one plage magnetogram shows stronger spatial correlation with unsigned vertical field, |B_z|, than either S_z or horizontal flux density, |B_h|. Title: Detection of Coherent Structures in Photospheric Turbulent Flows Authors: Chian, Abraham C. -L.; Rempel, Erico L.; Aulanier, Guillaume; Schmieder, Brigitte; Shadden, Shawn C.; Welsch, Brian T.; Yeates, Anthony R. Bibcode: 2014ApJ...786...51C Altcode: 2013arXiv1312.2405C We study coherent structures in solar photospheric flows in a plage in the vicinity of the active region AR 10930 using the horizontal velocity data derived from Hinode/Solar Optical Telescope magnetograms. Eulerian and Lagrangian coherent structures (LCSs) are detected by computing the Q-criterion and the finite-time Lyapunov exponents of the velocity field, respectively. Our analysis indicates that, on average, the deformation Eulerian coherent structures dominate over the vortical Eulerian coherent structures in the plage region. We demonstrate the correspondence of the network of high magnetic flux concentration to the attracting Lagrangian coherent structures (aLCSs) in the photospheric velocity based on both observations and numerical simulations. In addition, the computation of aLCS provides a measure of the local rate of contraction/expansion of the flow. Title: The coronal energy input from magnetic braiding Authors: Yeates, A. R.; Bianchi, F.; Welsch, B. T.; Bushby, P. J. Bibcode: 2014A&A...564A.131Y Altcode: 2014arXiv1403.4396Y We estimate the energy input into the solar corona from photospheric footpoint motions, using observations of a plage region by the Hinode Solar Optical Telescope. Assuming a perfectly ideal coronal evolution, two alternative lower bounds for the Poynting flux are computed based on field line footpoint trajectories, without requiring horizontal magnetic field data. When applied to the observed velocities, a bound based solely on displacements between the two footpoints of each field line is tighter than a bound based on relative twist between field lines. Depending on the assumed length of coronal magnetic field lines, the higher bound is found to be reasonably tight compared with a Poynting flux estimate using an available vector magnetogram. It is also close to the energy input required to explain conductive and radiative losses in the active region corona. Based on similar analysis of a numerical convection simulation, we suggest that observations with higher spatial resolution are likely to bring the bound based on relative twist closer to the first bound, but not to increase the first bound substantially. Finally, we put an approximate upper bound on the magnetic energy by constructing a hypothetical "unrelaxed" magnetic field with the correct field line connectivity. Title: Obtaining Photospheric Electric Field Maps and Poynting Fluxes from vector magnetograms and Doppler data: Tests and Data Driving Applications Authors: Kazachenko, Maria; Fisher, George; Welsch, Brian Bibcode: 2014cosp...40E1439K Altcode: Quantitative studies of the flow of magnetic energy through the solar photosphere require a knowledge of the magnetic field vector B - and knowledge of the electric field E as well. We have modified and improved the technique Fisher et al. developed in 2012, which combines a poloidal-toroidal decomposition (PTD) to determine contributions to E from Faraday's law, with additional non-inductive contributions arising from flux emergence near polarity inversion lines, determined from Doppler measurements. The new technique, which we call the ``PTD Doppler FLCT Ideal'' (or PDFI) technique, incorporates Doppler information from non-normal viewing angles, and adopts the faster and more robust FISHPACK software for solutions of the two-dimensional Poisson equations. We demonstrate the performance using synthetic data from the anelastic pseudo-spectral ANMHD simulations that were used in the recent comparison of velocity inversion techniques (Welsch et al. 2007) and the PTD inversion (Fisher et al. 2012). We find that the PDFI method has roughly 10% reconstruction errors (it predicts roughly 100% of the photospheric Poynting flux and 110% of the helicity flux rate at normal viewing angles, consistent with Fisher et al. (2012) results, and 90% of Poynting flux and 110% helicity flux at theta=30 degrees). We conclude that the PDFI method can be routinely applied to observed magnetic field data and, as an example, apply it to the 6-day HMI/SDO vector magnetogram sequence centered at AR11158, where an X2.2 flare occurred. We discuss how our electric field maps are used to drive coronal magnetic field with a global evolutionary model, or CGEM, a collaborative effort from the UC Berkeley Space Sciences Laboratory (SSL), Stanford University, and Lockheed-Martin. Title: Solar Magnetic Tracking. IV. The Death of Magnetic Features Authors: Lamb, D. A.; Howard, T. A.; DeForest, C. E.; Parnell, C. E.; Welsch, B. T. Bibcode: 2013ApJ...774..127L Altcode: 2013arXiv1307.4019L The removal of magnetic flux from the quiet-Sun photosphere is important for maintaining the statistical steady state of the magnetic field there, for determining the magnetic flux budget of the Sun, and for estimating the rate of energy injected into the upper solar atmosphere. Magnetic feature death is a measurable proxy for the removal of detectable flux, either by cancellation (submerging or rising loops, or reconnection in the photosphere) or by dispersal of flux. We used the SWAMIS feature tracking code to understand how nearly 2 × 104 magnetic features die in an hour-long sequence of Hinode/SOT/NFI magnetograms of a region of the quiet Sun. Of the feature deaths that remove visible magnetic flux from the photosphere, the vast majority do so by a process that merely disperses the previously detected flux so that it is too small and too weak to be detected, rather than completely eliminating it. The behavior of the ensemble average of these dispersals is not consistent with a model of simple planar diffusion, suggesting that the dispersal is constrained by the evolving photospheric velocity field. We introduce the concept of the partial lifetime of magnetic features, and show that the partial lifetime due to Cancellation of magnetic flux, 22 hr, is three times slower than previous measurements of the flux turnover time. This indicates that prior feature-based estimates of the flux replacement time may be too short, in contrast with the tendency for this quantity to decrease as resolution and instrumentation have improved. This suggests that dispersal of flux to smaller scales is more important for the replacement of magnetic fields in the quiet Sun than observed bipolar cancellation. We conclude that processes on spatial scales smaller than those visible to Hinode dominate the processes of flux emergence and cancellation, and therefore also the quantity of magnetic flux that threads the photosphere. Title: Deriving Potential Fields from Vector Magnetograms Authors: Welsch, Brian Bibcode: 2013SPD....44..118W Altcode: The minimum-energy state for the magnetic field above the solar photosphere is current-free. Since current is proportional to the magnetic field's curl, the minimum energy state is curl-free, and can therefore be represented as the gradient of a scalar potential. In addition, the divergence-free condition on the magnetic field implies this scalar potential obeys Laplace's equation. An appropriate boundary condition must be specified to determine the potential. Given a measurement of the full magnetic vector at the photosphere, it is possible to employ either Neumann or Dirichlet boundary conditions there. Typically, the Neumann condition is applied. Since either condition fully specifies the three-dimensional vector magnetic field, either choice will, in general, be inconsistent with some aspect of the observed field on the boundary, due to the presence of both currents and noise in the observed field. We present a method to derive a potential field that minimizes the integrated square of the residual between both boundary conditions, and show one way to incorporate weighting by spatially uniform measurement uncertainties in the minimization. We demonstrate each approach using HMI vector magnetic field observations of AR 11158. Residual discrepancies between the observed and potential fields are significantly larger than empirically determined noise levels, and can be interpreted as evidence of horizontal photospheric currents. The data provide clues about properties of these currents, but determining their spatial distribution will require additional constraints, e.g., simplifying assumptions about photospheric magnetic structure or observational input beyond single-height magnetograms. We also find that the energies of potential fields computed in different ways are significantly different --- by nearly 1e+33 ergs in some cases. This has substantial implications for estimates of the free magnetic energy in coronal field models that is available to power flares and coronal mass ejections (CMEs.) Title: A Magnetic Calibration of Photospheric Doppler Velocities Authors: Welsch, Brian T.; Fisher, George H.; Sun, Xudong Bibcode: 2013ApJ...765...98W Altcode: 2012arXiv1201.2451W The zero point of measured photospheric Doppler shifts is uncertain for at least two reasons: instrumental variations (from, e.g., thermal drifts); and the convective blueshift, a known correlation between intensity and upflows. Accurate knowledge of the zero point is, however, useful for (1) improving estimates of the Poynting flux of magnetic energy across the photosphere, and (2) constraining processes underlying flux cancellation, the mutual apparent loss of magnetic flux in closely spaced, opposite-polarity magnetogram features. We present a method to absolutely calibrate line-of-sight (LOS) velocities in solar active regions (ARs) near disk center using three successive vector magnetograms and one Dopplergram coincident with the central magnetogram. It exploits the fact that Doppler shifts measured along polarity inversion lines (PILs) of the LOS magnetic field determine one component of the velocity perpendicular to the magnetic field, and optimizes consistency between changes in LOS flux near PILs and the transport of transverse magnetic flux by LOS velocities, assuming that ideal electric fields govern the magnetic evolution. Previous calibrations fitted the center-to-limb variation of Doppler velocities, but this approach cannot, by itself, account for residual convective shifts at the limb. We apply our method to vector magnetograms of AR 11158, observed by the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory, and find clear evidence of offsets in the Doppler zero point in the range of 50-550 m s-1. In addition, we note that a simpler calibration can be determined from an LOS magnetogram and Dopplergram pair from the median Doppler velocity among all near-disk-center PIL pixels. We briefly discuss shortcomings in our initial implementation, and suggest ways to address these. In addition, as a step in our data reduction, we discuss the use of temporal continuity in the transverse magnetic field direction to correct apparently spurious fluctuations in resolution of the 180° ambiguity. Title: Interpreting Magmatic Processes from Clinopyroxene in Terrestrial Ankaramite Lavas: A Procedural Blueprint for the Nakhlites? Authors: Jacob, S. R.; Hammer, J. E.; Welsch, B. Bibcode: 2013LPI....44.3084J Altcode: 2013LPICo1719.3084J We looked at clinopyroxene crystals from a Maui ankaramite lava flow as a possible analog to the martian nakhlites. Title: Photospheric Drivers of Coronal Evolution Authors: Welsch, B. T.; Kazachenko, M.; Fisher, G. H.; Cheung, M. C. M.; DeRosa, M. L.; CGEM Team Bibcode: 2013enss.confE.108W Altcode: Flares and coronal mass ejections (CMEs) are driven by the release of free magnetic energy stored in the coronal magnetic field. While this energy is stored in the corona, photospheric driving must play a central role in its injection, storage, and release, since magnetic fields present in the corona originated within the solar interior, and are anchored at the photosphere. Also, the corona's low diffusivity and high Alfven speed (compared to that at the photosphere) imply that the large-scale coronal field essentially maintains equilibrium (outside of episodic flares and CMEs!), and therefore only evolves due to forcing from photospheric evolution. But fundamental questions about each stage of this "storage and release" paradigm remain open: How does free magnetic energy build up in the corona? How is this energy stored? And what triggers its release? The unprecedented combination of high cadence, resolution, and duty cycle of the HMI vector magnetograph enables modeling coronal magnetic evolution in response to photospheric driving, a powerful approach to addressing these questions. I will discuss our efforts to use HMI vector magneotgrams of AR 11158 to derive time-dependent boundary conditions for a data-driven coronal magnetic field model. These efforts will play a key role in the planned Coronal Global Evolutionary Model (CGEM), a data-driven, time-dependent model of the global coronal field. This work is supported by NASA's Living With a Star program and NSF's Division of Atmospheric and Geospace Sciences. Title: Thermal History of Yamato 980459: Constraints from Mineralogy, Crystal Morphology, and Dynamic Cooling Experiments Authors: First, E.; Hammer, J.; Welsch, B. Bibcode: 2013LPI....44.2943F Altcode: 2013LPICo1719.2943F We seek to constrain the thermal history of Y-98 through thin section analysis of the meteorite and 1-atm dynamic cooling experiments on a synthetic equivalent. Title: Lagrangian coherent structures in the solar magnetoconvective turbulence Authors: Chian, A. C.; Rempel, E. L.; Welsch, B. T.; Yeates, A. R. Bibcode: 2012AGUFMSH51B2244C Altcode: Turbulence and chaos play a fundamental role in solar convection through the transport of particles, energy, and momentum. Lagrangian coherent structures (LCS), which are material lines or surfaces that act as transport barriers in the plasma, provide a novel method to describe plasma turbulent motions (ApJL 735, L9, 2011; A&A 539, A1, 2012). We report the detection of LCS in numerical simulation of turbulent dynamo and Hinode observation of turbulent flows in the solar photosphere. In a 3-D helical MHD dynamo simulations of an Arnold-Beltrami-Childress flow, two dynamo regimes, a traveling wave regime and an intermittent regime, are identified as the magnetic diffusivity is varied. The sharp contrast between the chaotic tangle of attracting and repelling LCS in both regimes permits a unique understanding of the impact of the magnetic field on the velocity field. Next, we apply the LCS method to study the photospheric flows derived from Hinode/SOT magnetograms in the NOAA active region AR 10930. It is shown that the generation of a network of quasi-separatrix layers in the magnetic field correspond to LCS in the photospheric velocity. Finally, the characteristics of LCS in numerical simulations and Hinode observations are compared. Title: Evolution of the Photospheric Vector Magnetic Field in HMI Data Authors: Welsch, B. T.; Fisher, G. H. Bibcode: 2012AGUFMSH13A2243W Altcode: We discuss aspects of magnetic field structure and evolution in HMI data, including artifacts of the observation procedure and data reduction, and characterization of noise in the magnetic variables and their rates of change. Title: Global Energetics of Thirty-eight Large Solar Eruptive Events Authors: Emslie, A. G.; Dennis, B. R.; Shih, A. Y.; Chamberlin, P. C.; Mewaldt, R. A.; Moore, C. S.; Share, G. H.; Vourlidas, A.; Welsch, B. T. Bibcode: 2012ApJ...759...71E Altcode: 2012arXiv1209.2654E We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between 2002 February and 2006 December, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the Geostationary Operational Environmental Satellite 1-8 Å band, (2) the total energy radiated from the soft X-ray (SXR) emitting plasma, (3) the peak energy in the SXR-emitting plasma, (4) the bolometric radiated energy over the full duration of the event, (5) the energy in flare-accelerated electrons above 20 keV and in flare-accelerated ions above 1 MeV, (6) the kinetic and potential energies of the coronal mass ejection (CME), (7) the energy in solar energetic particles (SEPs) observed in interplanetary space, and (8) the amount of free (non-potential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in flare-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of flare-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the flare-accelerated particles, and the hot thermal plasma. Title: Are Decaying Magnetic Fields Above Active Regions Related to Coronal Mass Ejection Onset? Authors: Suzuki, J.; Welsch, B. T.; Li, Y. Bibcode: 2012ApJ...758...22S Altcode: 2012arXiv1211.4684S Coronal mass ejections (CMEs) are powered by magnetic energy stored in non-potential (current-carrying) coronal magnetic fields, with the pre-CME field in balance between outward magnetic pressure of the proto-ejecta and inward magnetic tension from overlying fields that confine the proto-ejecta. In studies of global potential (current-free) models of coronal magnetic fields—Potential Field Source Surface (PFSS) models—it has been reported that model field strengths above flare sites tend to be weaker when CMEs occur than when eruptions fail to occur. This suggests that potential field models might be useful to quantify magnetic confinement. One straightforward implication of this idea is that a decrease in model field strength overlying a possible eruption site should correspond to diminished confinement, implying an eruption is more likely. We have searched for such an effect by post facto investigation of the time evolution of model field strengths above a sample of 10 eruption sites. To check if the strengths of overlying fields were relevant only in relatively slow CMEs, we included both slow and fast CMEs in our sample. In most events we study, we find no statistically significant evolution in either (1) the rate of magnetic field decay with height, (2) the strength of overlying magnetic fields near 50 Mm, or (3) the ratio of fluxes at low and high altitudes (below 1.1 R ⊙, and between 1.1 and 1.5 R ⊙, respectively). We did observe a tendency for overlying field strengths and overlying flux to increase slightly, and their rates of decay with height to become slightly more gradual, consistent with increased confinement. The fact that CMEs occur regardless of whether the parameters we use to quantify confinement are increasing or decreasing suggests that either (1) the parameters that we derive from PFSS models do not accurately characterize the actual large-scale field in CME source regions, (2) systematic evolution in the large-scale magnetic environment of CME source regions is not, by itself, a necessary condition for CMEs to occur, or both. Title: The evolution of the electric field and the Poynting and Helicity Fluxes in NOAA AR 11158 Authors: Kazachenko, Maria D.; Fisher, George H.; Welsch, Brian T. Bibcode: 2012shin.confE..44K Altcode: The existence of systematic measurements of vector magnetic fields and Doppler shifts allows us to estimate electric field in the photosphere, by solving Faraday's law, using a Poloidal-Toroidal Decomposition (PTD) of the magnetic field and its partial time derivative, as well as incorporating information from Doppler shifts (Fisher et al. 2012). The method is based on solving a set of two-dimensional Poisson equations. We have recently modified the method in the following two ways. First, we improvedthe speed and accuracy of the Poisson equation solver using the FISHPACK elliptic partial differential equation software developed at NCAR, employing Neumann boundary conditions appropriate for zero electric fields on the vector-magnetogram boundary. Second, we developed a more general procedure which allows us to calculate electric fields from magnetic fields observed at non-zero viewing angles. We apply the improved technique to ANMHD-simulation test case with a known electric field and find that it yields more accurate values of Electric field, Poynting and helicity fluxes than before. We then apply our method to three-days-long HMI data-set centered on AR 11158, which produced an X2.2 flare. We present our first results of electric field, helicity and Poynting flux evolutions in AR 11158. Title: Using Electric Fields to drive simulations of the solar coronal magnetic field Authors: Fisher, George H.; Cheung, Mark; DeRosa, Marc; Kazachenko, Maria; Welsch, Brian; Hoeksema, Todd; Sun, Xudong Bibcode: 2012shin.confE..47F Altcode: The availability of high-cadence vector magnetograms and Doppler flow information measured from the HMI instrument on SDO make it possible to determine the electric field at the solar photosphere. This electric field, in turn, can be used to drive time-dependent simulations of the magnetic field in the solar corona, employing the MHD equations, or simpler time-dependent models such as the magneto-frictional (MF) model. Here, we demonstrate these concepts by using electric fields determined from HMI data to drive a time-dependent MF model of the solar corona in the volume overlying the photosphere near NOAA AR 11158. Title: New Directions for Improving Estimating Electric Fields from Magnetograms Authors: Welsch, Brian T. Bibcode: 2012shin.confE..43W Altcode: Via Faraday's law, sequences of photospheric vector magnetograms can be used to derive electric fields in the atmospheric layer imaged bythe magnetograph. These electric field estimates have applications for space weather prediction: they determine the Poynting flux of energy across the area imaged by the magnetogam, and can be used to drive time-dependent models of the coronal magnetic field. Tests of current approaches for estimating electric fields using artificial data from MHD simulations of photospheric magnetic evolution reveal that electric field estimation methods are imperfect in several respects; most notably, the estimated electric fields underestimated the fluxes of magnetic energy and helicity in some circumstances. Here, I will outline some speculative approaches that might improve the accuracy of electric field estimates. Title: Global Energetics of Large Solar Eruptive Events Authors: Dennis, Brian R.; Emslie, A. G.; Chamberlin, P. C.; Mewaldt, R. A.; Moore, C. S.; Share, G. H.; Shih, A. Y.; Vourlidas, A.; Welsch, B. Bibcode: 2012AAS...22041002D Altcode: We have evaluated the energetics of the larger solar eruptive events recorded with a variety of spacecraft instruments between February 2002 and December 2006. All of the energetically important components of the flares and of the accompanying coronal mass ejections and solar energetic particles have been evaluated as accurately as the observations allow. These components include the following: (1) the total energy in the high temperature plasma determined from the RHESSI thermal X-ray observations; (2) the total energies in accelerated electrons above 20 keV and ions above 1 MeV from RHESSI hard X-ray and gamma-ray observations, respectively; (3) the potential and kinetic energies of the CME from SOHO/LASCO observations; (4) the solar energetic particle (SEP) energy estimates from in situ measurements on ACE, GOES, and SOHO; (5) the total radiated energy from the SORCE/TSI measurements where available, and otherwise from the Flare Irradiance Spectral Model (FISM). The results are assimilated and discussed relative to the probable amount of nonpotential magnetic energy estimated to be available in the flaring active regions from MDI line-of-sight magnetograms. Title: Global Forces in Eruptive Solar Flares: The Lorentz Force Acting on the Solar Atmosphere and the Solar Interior Authors: Fisher, George H.; Bercik, D. J.; Welsch, B. T.; Hudson, H. S. Bibcode: 2012AAS...22020440F Altcode: We compute the change in the Lorentz force integrated over the outer solar atmosphere implied by observed changes in vector magnetograms that occur during large, eruptive solar flares. This force perturbation should be balanced by an equal and opposite force perturbation acting on the solar photosphere and solar interior. The resulting expression for the estimated force change in the solar interior generalizes the earlier expression presented by Hudson, Fisher, and Welsch, providing horizontal as well as vertical force components, and provides a more accurate result for the vertical component of the perturbed force. We show that magnetic eruptions should result in the magnetic field at the photosphere becoming more horizontal, and hence should result in a downward (toward the solar interior) force change acting on the photosphere and solar interior, as recently argued from an analysis of magnetogram data by Wang and Liu. We suggest the existence of an observational relationship between the force change computed from changes in the vector magnetograms, the outward momentum carried by the ejecta from the flare, and the properties of the helioseismic disturbance driven by the downward force change. We use the impulse driven by the Lorentz-force change in the outer solar atmosphere to derive an upper limit to the mass of erupting plasma that can escape from the Sun. Finally, we compare the expected Lorentz-force change at the photosphere with simple estimates from flare-driven gasdynamic disturbances and from an estimate of the perturbed pressure from radiative backwarming of the photosphere in flaring conditions. Title: Finding Electric Fields, Poynting and Helicity Fluxes from Vector Magnetograms Authors: Kazachenko, Maria; Fisher, G. H.; Welsch, B. T. Bibcode: 2012AAS...22020210K Altcode: Existence of systematic measurements of vector magnetic fields allows us to estimate electric field in the photosphere, using Poloidal-Toroidal Decomposition of the magnetic field and its partial time derivative (Fisher et l. 2011). The PTD method is based on solving a set of Poisson equations which in the past has been done using Fast Fourier Transform techniques. We modify the existing PTD method by improving the poisson solver using a package of solvers for elliptic partial differential equations called Fishpack. We apply the PTD with a new Poisson equation solver to several test cases with a known electric field. We find that for the ANMHD simulation test case application of the new poisson solver yields a more accurate values of electric field, Poisson and helicity fluxes than before. We further investigate the applicability of our method to other test cases using simulations of M. Cheung and Y. Fan and also HMI vector magnetograms. Title: A First Look at Magnetic Field Data Products from SDO/HMI Authors: Liu, Y.; Scherrer, P. H.; Hoeksema, J. T.; Schou, J.; Bai, T.; Beck, J. G.; Bobra, M.; Bogart, R. S.; Bush, R. I.; Couvidat, S.; Hayashi, K.; Kosovichev, A. G.; Larson, T. P.; Rabello-Soares, C.; Sun, X.; Wachter, R.; Zhao, J.; Zhao, X. P.; Duvall, T. L., Jr.; DeRosa, M. L.; Schrijver, C. J.; Title, A. M.; Centeno, R.; Tomczyk, S.; Borrero, J. M.; Norton, A. A.; Barnes, G.; Crouch, A. D.; Leka, K. D.; Abbett, W. P.; Fisher, G. H.; Welsch, B. T.; Muglach, K.; Schuck, P. W.; Wiegelmann, T.; Turmon, M.; Linker, J. A.; Mikić, Z.; Riley, P.; Wu, S. T. Bibcode: 2012ASPC..455..337L Altcode: The Helioseismic and Magnetic Imager (HMI; Scherrer & Schou 2011) is one of the three instruments aboard the Solar Dynamics Observatory (SDO) that was launched on February 11, 2010 from Cape Canaveral, Florida. The instrument began to acquire science data on March 24. The regular operations started on May 1. HMI measures the Doppler velocity and line-of-sight magnetic field in the photosphere at a cadence of 45 seconds, and the vector magnetic field at a 135-second cadence, with a 4096× 4096 pixels full disk coverage. The vector magnetic field data is usually averaged over 720 seconds to suppress the p-modes and increase the signal-to-noise ratio. The spatial sampling is about 0".5 per pixel. HMI observes the Fe i 6173 Å absorption line, which has a Landé factor of 2.5. These data are further used to produce higher level data products through the pipeline at the HMI-AIA Joint Science Operations Center (JSOC) - Science Data Processing (Scherrer et al. 2011) at Stanford University. In this paper, we briefly describe the data products, and demonstrate the performance of the HMI instrument. We conclude that the HMI is working extremely well. Title: Global Forces in Eruptive Solar Flares: The Lorentz Force Acting on the Solar Atmosphere and the Solar Interior Authors: Fisher, G. H.; Bercik, D. J.; Welsch, B. T.; Hudson, H. S. Bibcode: 2012SoPh..277...59F Altcode: 2010arXiv1006.5247F; 2011SoPh..tmp..419F; 2011SoPh..tmp..415F We compute the change in the Lorentz force integrated over the outer solar atmosphere implied by observed changes in vector magnetograms that occur during large, eruptive solar flares. This force perturbation should be balanced by an equal and opposite force perturbation acting on the solar photosphere and solar interior. The resulting expression for the estimated force change in the solar interior generalizes the earlier expression presented by Hudson, Fisher, and Welsch (Astron. Soc. Pac. CS-383, 221, 2008), providing horizontal as well as vertical force components, and provides a more accurate result for the vertical component of the perturbed force. We show that magnetic eruptions should result in the magnetic field at the photosphere becoming more horizontal, and hence should result in a downward (toward the solar interior) force change acting on the photosphere and solar interior, as recently argued from an analysis of magnetogram data by Wang and Liu (Astrophys. J. Lett. 716, L195, 2010). We suggest the existence of an observational relationship between the force change computed from changes in the vector magnetograms, the outward momentum carried by the ejecta from the flare, and the properties of the helioseismic disturbance driven by the downward force change. We use the impulse driven by the Lorentz-force change in the outer solar atmosphere to derive an upper limit to the mass of erupting plasma that can escape from the Sun. Finally, we compare the expected Lorentz-force change at the photosphere with simple estimates from flare-driven gasdynamic disturbances and from an estimate of the perturbed pressure from radiative backwarming of the photosphere in flaring conditions. Title: Can We Determine Electric Fields and Poynting Fluxes from Vector Magnetograms and Doppler Measurements? Authors: Fisher, G. H.; Welsch, B. T.; Abbett, W. P. Bibcode: 2012SoPh..277..153F Altcode: 2011arXiv1101.4086F The availability of vector-magnetogram sequences with sufficient accuracy and cadence to estimate the temporal derivative of the magnetic field allows us to use Faraday's law to find an approximate solution for the electric field in the photosphere, using a Poloidal-Toroidal Decomposition (PTD) of the magnetic field and its partial time derivative. Without additional information, however, the electric field found from this technique is under-determined - Faraday's law provides no information about the electric field that can be derived from the gradient of a scalar potential. Here, we show how additional information in the form of line-of-sight Doppler-flow measurements, and motions transverse to the line-of-sight determined with ad-hoc methods such as local correlation tracking, can be combined with the PTD solutions to provide much more accurate solutions for the solar electric field, and therefore the Poynting flux of electromagnetic energy in the solar photosphere. Reliable, accurate maps of the Poynting flux are essential for quantitative studies of the buildup of magnetic energy before flares and coronal mass ejections. Title: Electric Fields and Poynting Fluxes from Vector Magnetograms Authors: Fisher, G. H.; Welsch, B. T.; Abbett, W. P. Bibcode: 2012decs.confE..75F Altcode: The availability of vector-magnetogram sequences with sufficient accuracy and cadence to estimate the temporal derivative of the magnetic field allows us to use Faraday's law to find an approximate solution for the electric field in the photosphere, using a Poloidal-Toroidal Decomposition (PTD) of the magnetic field and its partial time derivative. Without additional information, however, the electric field found from this technique is under-determined - Faraday's law provides no information about the electric field that can be derived from the gradient of a scalar potential. Here, we show how additional information in the form of line-of-sight Doppler-flow measurements, and motions transverse to the line-of-sight determined with ad-hoc methods such as local correlation tracking, can be combined with the PTD solutions to provide much more accurate solutions for the solar electric field, and therefore the Poynting flux of electromagnetic energy in the solar photosphere. Reliable, accurate maps of the Poynting flux are essential for quantitative studies of the buildup of magnetic energy before flares and coronal mass ejections. Title: Determining electric fields from vector magnetograms. Authors: Kazachenko, M.; Fisher, G. H.; Welsch, B. T. Bibcode: 2012decs.confE..98K Altcode: Existence of systematic measurements of vector magnetic fields allows us to estimate electric field in the photosphere, using Poloidal-Toroidal Decomposition of the magnetic field and its partial time derivative (Fisher et l. 2011). The PTD method is based on solving a set of Poisson equations which in the past has been done using Fast Fourier Transform techniques. We modify the existing PTD method by improving the poisson solver using a package of solvers for elliptic partial differential equations called Fishpack. We apply the PTD with a new Poisson equation solver to several test cases with a known electric field. We find that for the ANMHD simulation test case application of the new poisson solver yields a more accurate values of electric field than before. We further investigate the applicability of our method to other test cases using simulations of M. Cheung and Y. Fan. Title: Decorrelation Times of Photospheric Fields and Flows Authors: Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Muglach, K. Bibcode: 2012ApJ...747..130W Altcode: 2011arXiv1110.6117W We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier local correlation tracking (FLCT) to a sequence of high-resolution (0farcs3), high-cadence (sime 2 minute) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the narrowband filter imager of the Solar Optical Telescope aboard the Hinode satellite over 2006 December 12 and 13. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms' susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Δt between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter σ used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, τ. For Δt > τ, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and Δt. Title: Lagrangian coherent structures in photospheric flows and their implications for coronal magnetic structure Authors: Yeates, A. R.; Hornig, G.; Welsch, B. T. Bibcode: 2012A&A...539A...1Y Altcode: 2011arXiv1110.3957Y
Aims: We show how the build-up of magnetic gradients in the Sun's corona may be inferred directly from photospheric velocity data. This enables computation of magnetic connectivity measures such as the squashing factor without recourse to magnetic field extrapolation.
Methods: Assuming an ideal evolution in the corona, and an initially uniform magnetic field, the subsequent field line mapping is computed by integrating trajectories of the (time-dependent) horizontal photospheric velocity field. The method is applied to a 12 h high-resolution sequence of photospheric flows derived from Hinode/SOT magnetograms.
Results: We find the generation of a network of quasi-separatrix layers in the magnetic field, which correspond to Lagrangian coherent structures in the photospheric velocity. The visual pattern of these structures arises primarily from the diverging part of the photospheric flow, hiding the effect of the rotational flow component: this is demonstrated by a simple analytical model of photospheric convection. We separate the diverging and rotational components from the observed flow and show qualitative agreement with purely diverging and rotational models respectively. Increasing the flow speeds in the model suggests that our observational results are likely to give a lower bound for the rate at which magnetic gradients are built up by real photospheric flows. Finally, we construct a hypothetical magnetic field with the inferred topology, that can be used for future investigations of reconnection and energy release.

Movies are available in electronic form at http://www.aanda.org Title: The Global Context of Solar Activity During the Whole Heliosphere Interval Campaign Authors: Webb, D. F.; Cremades, H.; Sterling, A. C.; Mandrini, C. H.; Dasso, S.; Gibson, S. E.; Haber, D. A.; Komm, R. W.; Petrie, G. J. D.; McIntosh, P. S.; Welsch, B. T.; Plunkett, S. P. Bibcode: 2011SoPh..274...57W Altcode: The Whole Heliosphere Interval (WHI) was an international observing and modeling effort to characterize the 3-D interconnected "heliophysical" system during this solar minimum, centered on Carrington Rotation 2068, March 20 - April 16, 2008. During the latter half of the WHI period, the Sun presented a sunspot-free, deep solar minimum type face. But during the first half of CR 2068 three solar active regions flanked by two opposite-polarity, low-latitude coronal holes were present. These departures from the quiet Sun led to both eruptive activity and solar wind structure. Most of the eruptive activity, i.e., flares, filament eruptions and coronal mass ejections (CMEs), occurred during this first, active half of the interval. We determined the source locations of the CMEs and the type of associated region, such as active region, or quiet sun or active region prominence. To analyze the evolution of the events in the context of the global solar magnetic field and its evolution during the three rotations centered on CR 2068, we plotted the CME source locations onto synoptic maps of the photospheric magnetic field, of the magnetic and chromospheric structure, of the white light corona, and of helioseismological subsurface flows. Most of the CME sources were associated with the three dominant active regions on CR 2068, particularly AR 10989. Most of the other sources on all three CRs appear to have been associated with either isolated filaments or filaments in the north polar crown filament channel. Although calculations of the flux balance and helicity of the surface magnetic features did not clearly identify a dominance of one region over the others, helioseismological subsurface flows beneath these active regions did reveal a pronounced difference among them. These preliminary results suggest that the "twistedness" (i.e., vorticity and helicity) of subsurface flows and its temporal variation might be related to the CME productivity of active regions, similar to the relationship between flares and subsurface flows. Title: Photospheric Magnetic Evolution in the WHI Active Regions Authors: Welsch, B. T.; Christe, S.; McTiernan, J. M. Bibcode: 2011SoPh..274..131W Altcode: 2011arXiv1103.2396W Sequences of line-of-sight (LOS) magnetograms recorded by the Michelson Doppler Imager are used to quantitatively characterize photospheric magnetic structure and evolution in three active regions that rotated across the Sun's disk during the Whole Heliosphere Interval (WHI), in an attempt to relate the photospheric magnetic properties of these active regions to flares and coronal mass ejections (CMEs). Several approaches are used in our analysis, on scales ranging from whole active regions, to magnetic features, to supergranular scales, and, finally, to individual pixels. We calculated several parameterizations of magnetic structure and evolution that have previously been associated with flare and CME activity, including total unsigned magnetic flux, magnetic flux near polarity-inversion lines, amount of canceled flux, the "proxy Poynting flux," and helicity flux. To catalog flare events, we used flare lists derived from both GOES and RHESSI observations. By most such measures, AR 10988 should have been the most flare- and CME-productive active region, and AR 10989 the least. Observations, however, were not consistent with this expectation: ARs 10988 and 10989 produced similar numbers of flares, and AR 10989 also produced a few CMEs. These results highlight present limitations of statistics-based flare and CME forecasting tools that rely upon line-of-sight photospheric magnetic data alone. Title: Roles for Data Assimilation in Studying Solar Flares & CMEs Authors: Welsch, B. T.; Abbett, W. P.; Fisher, G. H. Bibcode: 2011AGUFMSH54A..05W Altcode: Solar flares and coronal mass ejections (CMEs) are driven by the sudden release of free magnetic energy stored in electric currents the solar corona. While there is a consensus that free energy enters the corona from the solar interior, there is ongoing debate about the physical processes primarily responsible for transporting free energy into the corona and / or triggering its release once there. Since direct measurements of the coronal vector magnetic field, necessary to quantify coronal currents, are currently not feasible, it is hoped that modeling of the coronal field can improve our understanding of processes that drive the corona to flare and produce CMEs. Many coronal modeling efforts employ spectropolarimetric observations of the photosphere, which can be used to infer magnetic fields and flows there; the model then relates these photospheric measurements to coronal currents. Observations of coronal emission structures might also usefully inform coronal field models. Here, I will discuss different approaches to modeling the coronal magnetic field, using both photospheric and other data sets, and possible roles for data assimilation. Title: Can we Determine Electric Fields and Poynting Fluxes from Vector Magnetograms and Doppler Measurements? Authors: Fisher, G. H.; Welsch, B. T.; Abbett, W. P. Bibcode: 2011AGUFMSH33C..07F Altcode: The availability of vector magnetogram sequences with sufficient accuracy and cadence to estimate the time derivative of the magnetic field allows us to use Faraday's law to find an approximate solution for the electric field in the photosphere, using a Poloidal-Toroidal Decomposition (PTD) of the magnetic field and its partial time derivative. Without additional information, however, the electric field found from this technique is under-determined -- Faraday's law provides no information about the electric field that can be derived the gradient of a scalar potential. Here, we show how additional information in the form of line-of-sight Doppler flow measurements, and motions transverse to the line-of-sight determined with ad-hoc methods such as local correlation tracking, can be combined with the PTD solutions to provide much more accurate solutions for the solar electric field, and therefore the Poynting flux of electromagnetic energy in the solar photosphere. Reliable, accurate maps of the Poynting flux are essential for quantitative studies of the buildup of magnetic energy before flares and coronal mass ejections. This work was supported by the NASA Heliophysics Theory Program, the NASA Living-With-a-Star Program, and the NSF Geosciences Directorate Title: Decorrelation Times of Photospheric Fields and Flows Authors: Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Fisher, G. H. Bibcode: 2011AGUFMSH31A1989W Altcode: We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier Local Correlation Tracking (FLCT) to a sequence of high-resolution (0.3''), high-cadence (≃ 2 min.) line-of-sight magnetograms of NOAA AR 10930 recorded by SOT/NFI aboard the Hinode satellite over 12-13 December 2006. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structure as a function of spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms' susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Δ t between magnetogram pairs tracked; spatial binning applied to the magnetograms; and windowing parameter σ used in FLCT. In addition, we tracked both boxcar-averaged and unaveraged magnetograms. Because flow structures are thought to vary over a range of spatial and temporal scales in the photospheric plasma (including unresolved scales), we suggest that estimated flows necessarily represent a local average of the flow pattern over space and time, and argue that flow decorrelation times should be at least as long as Δ t to meaningfully estimate plasma velocities. When Δ t exceeds the flow decorrelation time, then displacements inferred from tracking represent the average velocity over more than one flow lifetime. We also analyze decorrelation times of flow components, divergences, and curls as functions of spatial scale and magnetic field strength. Title: A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval Authors: Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.; Jackson, Bernard V.; Jensen, Elizabeth A.; Leamon, Robert J.; Lei, Jiuhou; Manoharan, Periasamy K.; Mays, M. Leila; McIntosh, Patrick S.; Petrie, Gordon J. D.; Plunkett, Simon P.; Qian, Liying; Riley, Peter; Suess, Steven T.; Tokumaru, Munetoshi; Welsch, Brian T.; Woods, Thomas N. Bibcode: 2011SoPh..274...29T Altcode: 2011SoPh..tmp..413T We present an overview of the data and models collected for the Whole Heliosphere Interval, an international campaign to study the three-dimensional solar-heliospheric-planetary connected system near solar minimum. The data and models correspond to solar Carrington Rotation 2068 (20 March - 16 April 2008) extending from below the solar photosphere, through interplanetary space, and down to Earth's mesosphere. Nearly 200 people participated in aspects of WHI studies, analyzing and interpreting data from nearly 100 instruments and models in order to elucidate the physics of fundamental heliophysical processes. The solar and inner heliospheric data showed structure consistent with the declining phase of the solar cycle. A closely spaced cluster of low-latitude active regions was responsible for an increased level of magnetic activity, while a highly warped current sheet dominated heliospheric structure. The geospace data revealed an unusually high level of activity, driven primarily by the periodic impingement of high-speed streams. The WHI studies traced the solar activity and structure into the heliosphere and geospace, and provided new insight into the nature of the interconnected heliophysical system near solar minimum. Title: Are Decaying Magnetic Fields Above Active Regions Related to CME Onset? Authors: Suzuki, J.; Welsch, B. T.; Li, Y. Bibcode: 2011AGUFMSH23A1938S Altcode: Coronal mass ejections (CMEs) are powered by magnetic energy stored in non-potential (current-carrying) coronal magnetic fields; the pre-CME field is thought to exhibit a balance between outward magnetic pressure of the proto-ejecta and inward magnetic tension from overlying fields that confine the proto-ejecta. In global potential (current-free) models of coronal magnetic fields --- potential field source-surface (PFSS) models --- above flare sites where CMEs originated, it has been noted that model field strengths are larger above sites where eruptions fail, suggesting potential field models might be useful to quantify magnetic confinement. One straightforward implication of this idea is that a decrease in model field strength overlying a possible eruption site should correspond to diminished confinement, implying an eruption is more likely. We have searched for such an effect by post facto investigation of the time evolution of model field strengths above a sample of 10 eruption sites. To check if the strengths of overlying fields were relevant only in relatively slow CMEs, we included both slow and fast CMEs in our sample. Title: Evolution and Activity of Solar Active Regions with STEREO Full Sun Imaging Authors: Li, Y.; Welsch, B. T.; Lynch, B. J.; Luhmann, J. G.; Fisher, G. H. Bibcode: 2011AGUFMSH13A1927L Altcode: Solar active regions emerge from the interior of the Sun. It is believed that the solar dynamo at the shear layer at the bottom of the convection zone generates flux ropes, which emerge to the photosphere as active regions. The active regions emerge with stressed and concentrated magnetic field up to a few thousand Gauss. Following the emerging phase, the field evolves and decays. The decay process of active regions is not fully understood. Active regions usually have multiple flares and CMEs. Solar eruptions consume magnetic free energy in active regions and eject field and mass away from the Sun. Solar eruptions may play a role in the decay of the magnetic field in active regions. The lifetime of active regions range from hours to perhaps a few months. Stronger active regions usually live longer than the earth view pass. We had always a single view of the Sun before STEREO. Using the full sun imaging of the STEREO mission, we study a few recent active regions on the rise phase of solar cycle 24. When the regions are in earth view, we analyze HMI magnetograms for the field and energy evolution. By observing the total number of flares and CMEs from each region using STEREO coronal images, we estimate the released energy through the lifetime of these active regions. We discuss the implications to active region energy budget and active region decay. Title: Momentum Balance in Eruptive Solar Flares: The Lorentz Force Acting on the Solar Atmosphere and the Solar Interior Authors: Fisher, George H.; Bercik, David J.; Welsch, Brian T.; Hudson, Hugh S. Bibcode: 2011sdmi.confE...9F Altcode: We compute the change in the Lorentz force integrated over the outer solar atmosphere implied by observed changes in vector magnetograms that occur during large, eruptive solar flares. This force perturbation should be balanced by an equal and opposite force perturbation acting on the solar photosphere and solar interior. The resulting expression for the estimated force change in the solar interior generalizes the earlier expression presented by Hudson, Fisher & Welsch (2008), providing horizontal as well as vertical force components, and provides a more accurate result for the vertical component of the perturbed force. We show that magnetic eruptions should result in the magnetic field at the photosphere becoming more horizontal, and hence should result in a downward (towards the solar interior) force change acting on the photosphere and solar interior, as recently argued from an analysis of magnetogram data by Wang & Liu. We suggest that there should be an observational relationship between the force change computed from changes in the vector magnetograms, the outward momentum carried by the ejecta from the flare, and the amplitude of the helioseismic disturbance driven by the downward force change. We use the impulse driven by the Lorentz force change in the outer solar atmosphere to derive an upper limit to the mass of erupting plasma that can escape from the Sun. Finally, we compare the expected Lorentz force change at the photosphere with simple estimates from flare-driven gasdynamic disturbances and from an estimate of the perturbed pressure from radiative backwarming of the photosphere in flaring conditions. Title: Understanding Links Between the Interior and Atmosphere Authors: Welsch, Brian T. Bibcode: 2011sdmi.confE..11W Altcode: Magnetic coupling between the solar interior and atmosphere is responsible for many phenomena that interest solar physicists, including atmospheric heating, solar flares, and coronal mass ejections (CMEs). While all these processes release magnetic energy stored in the atmosphere, that energy originated within the solar interior, and the magnetic fields involved are also tethered to the interior. The precise mechanisms by which magnetic energy passes from the interior into the atmosphere to drive such phenomena, however, remain poorly understood. For instance, statistical relationships have been reported between solar flares and the structure and evolution of subsurface flows, inferred from ring diagram analysis; but we can only speculate about the physics underlying such relationships. In addition, we cannot yet say if or how processes in the atmosphere feed back into the interior. For instance, does most active region magnetic flux submerge back into the interior? Or does it escape outward into the atmosphere? I will discuss some open questions regarding magnetic coupling between the interior and atmosphere, and consider ways that the HMI and AIA instruments aboard SDO might be used to address such questions -- with input from the audience welcomed!