Use of Magnetic Field Modeling and Topology Analysis in Understanding the Evolution and Eruption of Coronal Sigmoids

Abstract:

Coronal sigmoids, generally ovserved in X-rays and EUV, are S-shaped active regions that have been shown to possess high probability for eruption. They present a direct evidence of the existence of flux ropes in the corona prior to the impulsive phase of eruptions. In order to gain insight into their eruptive behavior and how they get destabilized we need to know their 3D magnetic field structure. We have performed highly data-constrained non-linear force-free field (NLFFF) models over the lifetime of several sigmoidal active regions and more specifically have captured their magnetic field structure around the times of major flares. We present this analysis of one region. We also look at the topology analysis for several sigmoidal regions and we show the probable sites of reconnection and put forward a scenario for eruption. We demonstrate the use of this topology analysis to reconcile the observed eruption features with the standard flare model. Finally, we show a glimpse of how such a NLFFF model of an erupting region can be used to initiate a CME in a global MHD code in an unprecedented realistic manner.