Magnetic Field Modeling of Complex, Flare Productive Active Regions

We present models and analysis of the magnetic field structure of three sigmoidal active regions (ARs). Sigmoids, forward or backward S-shaped EUV and X-ray emissions in the corona, are relevant as predictors of eruptive events such as flares and Coronal Mass Ejections. The regions were modeled using the Flux Rope Insertion Method, in which flux ropes, held in equilibrium by an overlying potential arcade, represent the sigmoids. The flux rope paths were inserted into a potential field following the filaments observed in 304Å. The models were then relaxed into a nonlinear force free (NLFFF) state using a magnetofrictional relaxation process.

The first region studied is NOAA AR 12017, which produced an X1.0 flare at 2014/03/29 17:35. The second is NOAA AR 11283, which erupted with an X2.1 flare at 2011/09/06 22:12. For these regions, we show detailed comparisons of Quasi-Separatrix Layer (QSL) maps and observed flare ribbons. The slow evolution of an unstable solution at the time of the eruption produces a set of QSL solutions. Comparison of the photospheric mapping of the QSL with the flare ribbons will be a good measure of how well we have captured the magnetic structure of the particle acceleration region with our simple NLFFF models.

The third is NOAA AR 11093. This region was a double decker filament composed of two branches over the same polarity inversion line. At 2010/08/07 17:55, the upper filament erupted with an M1.0 flare. This is the first time a double decker flux rope region has been modeled using these techniques. We show the interaction of the two inserted flux ropes and the evolution of the region through a series of NLFFF solutions to the evolving photospheric magnetic field.

This work has been funded by the NSF-REU solar physics program at Smithsonian Astrophysical Observatory, grant number AGS-1263241.