Temporal and spatial relationship of flare signatures and the force-free coronal magnetic field

TL;DR

This study combines multi-wavelength observations and 3D magnetic field modeling to analyze the evolution of flare signatures, magnetic reconnection, and energy release in an active solar region, providing new insights into flare dynamics.

Contribution

It introduces a method to estimate the elevation speed of the current sheet's tip during a flare using combined observational and modeling data, and demonstrates magnetic field implosion and energy loss.

Findings

Estimated the current sheet's tip speed at a few km/s.

Provided evidence for magnetic field implosion during the flare.

Linked magnetic energy buildup to sheared magnetic fields.

Abstract

We investigate the plasma and magnetic environment of active region NOAA 11261 on 2 August 2011 around a GOES M1.4 flare/CME (SOL2011-08-02T06:19). We compare coronal emission at (extreme) ultraviolet and X-ray wavelengths, using SDO AIA and RHESSI images, in order to identify the relative timing and locations of reconnection-related sources. We trace flare ribbon signatures at ultraviolet wavelengths, in order to pin down the intersection of previously reconnected flaring loops at the lower solar atmosphere. These locations are used to calculate field lines from 3D nonlinear force-free magnetic field models, established on the basis of SDO HMI photospheric vector magnetic field maps. With this procedure, we analyze the quasi-static time evolution of the coronal model magnetic field previously involved in magnetic reconnection. This allows us, for the first time, to estimate the elevation speed of the current sheet's lower tip during an on-disk observed flare, as a few kilometers per second. Comparison to post-flare loops observed later above the limb in STEREO EUVI images supports this velocity estimate. Furthermore, we provide evidence for an implosion of parts of the flaring coronal model magnetic field, and identify the corresponding coronal sub-volumes associated to the loss of magnetic energy. Finally, we spatially relate the build up of magnetic energy in the 3D models to highly sheared fields, established due to dynamic relative motions of polarity patches within the active region.