Photospheric and Coronal Observations of Abrupt Magnetic Restructuring in Flaring Active Regions

Abstract:

The Lorentz force changes associated with strong photospheric fields in large structures within active regions can be estimated from time series of Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) vector magnetograms. The major, most organized changes tend to occur close to the centers of flaring regions, near the main neutral line and/or in twisted sunspots. Fields close to the neutral line tend to collapse downward and inward, consistent with compression rather than rotation of the vector field. In sunspots the twist (or azimuthal component around the sunspot axis) tends to decrease. In a limited number of cases particularly well-observed by the Atmospheric Imaging Assembly (AIA) on SDO and the Extreme Ultraviolet Imager (EUVI) on the Solar TErrestrial RElations Observatory (STEREO), the evolution of the photospheric magnetic vector field can be related to changes in coronal magnetic structure to provide a coherent description of the magnetic changes during the different phases of a flare.

This work was supported by NASA grant NNX14AE05G.