Thesis Open Access

Abstract: 3D Model of Slip-Running Reconnection on Solar Sigmoidal Regions

Douglas, Brianna

Thesis supervisor(s)

Savcheva, Antonia; DeLuca, Edward

The structure of energy storing magnetic field lines on the Sun is very twisted and contorted. Some of the twist arises from photospheric foot point motion and some is due to currents carried into the corona as fields emerge. The stability of a region depends on both the energy stored (so-called “free” energy) and on the structure of the surrounding nearly potential fields. Free energy is usually contained in these S-shaped regions called sigmoids on the solar corona. The only way to reach lower energy state is to release this free energy, by changing its connectivity. This change in connectivity leads to flares and coronal mass ejections (CMEs) that can affect environments of nearby planets. For this project, we focus on a special kind of connectivity change called slip-running reconnection to create 3D numerical models of flare-producing magnetic fields. By comparing these numerical models to observational data from Atmospheric Imaging Assembly (AIA), we will be able to better explain the evolution of sigmoidal flares from active regions. We are studying a flare from  Dudik et al 2014 paper (2012 July 12), and a flare from 2015 June 14. Using the Coronal Modeling System (CMS) software, we read the photospheric magnetogram for the specified date and time, compute the potential field, setup the 3D flux rope path, and then relax this flux rope over 60,000 iterations to create a nonlinear force-free field (NLFFF). Using these relaxed models we find the best-fit loops surrounding the flux rope. We then compare these models to the observations in AIA. We compare the magnetic field structure in our models with the observed slipping. For regions near our inserted flux rope, our models successfully correlate with this observation. Further modeling is required, but these initial results suggest that NLFFF modeling may be able to capture realistic 3-D magnetic structures associated with slipping reconnection.

This work is supported by NSF-REU Solar Physics Program at SAO, grant number AGS 1263241 and AFOSR Grant Z15-12504 "Toward Improved Space Weather Prediction Through the Observation and Modeling of Coronal Magnetism".
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