Evolution of flare ribbons, electric currents, and quasi-separatrix layers during an X-class flare

Abstract

Context. The standard model for eruptive flares has been extended to three dimensions (3D) in the past few years. This model predicts typical J-shaped photospheric footprints of the coronal current layer, forming at similar locations as the quasi-separatrix layers (QSLs). Such a morphology is also found for flare ribbons observed in the extreme ultraviolet (EUV) band, and in nonlinear force-free field (NLFFF) magnetic field extrapolations and models. Aims. We study the evolution of the photospheric traces of the current density and flare ribbons, both obtained with the Solar Dynamics Observatory instruments. We aim to compare their morphology and their time evolution, before and during the flare, with the topological features found in a NLFFF model. Methods. We investigated the photospheric current evolution during the 06 September 2011 X-class flare (SOL2011-09-06T22:20) occurring in NOAA AR 11283 from observational data of the magnetic field obtained with the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory. We compared this evolution with that of the flare ribbons observed in the EUV filters of the Atmospheric Imager Assembly. We also compared the observed electric current density and the flare ribbon morphology with that of the QSLs computed from the flux rope insertion method-NLFFF model.Results. The NLFFF model shows the presence of a fan-spine configuration of overlying field lines, due to the presence of a parasitic polarity, embedding an elongated flux rope that appears in the observations as two parts of a filament. The QSL signatures of the fan configuration appear as a circular flare ribbon that encircles the J-shaped ribbons related to the filament ejection. The QSLs, evolved via a magnetofrictional method, also show similar morphology and evolution as both the current ribbons and the EUV flare ribbons obtained several times during the flare. Conclusions. For the first time, we propose a combined analysis of the photospheric traces of an eruptive flare, in a complex topology, with direct measurements of electric currents and QSLs from observational data and a magnetic field model. The results, obtained by two different and independent approaches 1) confirm previous results of current increase during the impulsive phase of the flare and 2) show how NLFFF models can capture the essential physical signatures of flares even in a complex magnetic field topology.

Vortex and Sink Flows in Eruptive Flares as a Model for Coronal Implosions

“…Cheng et al 2010;Zhang et al 2012;Patsourakos et al 2013;Cheng et al 2013;Dudík et al 2014;Cheng et al 2014aCheng et al ,b, 2015 have both been interpreted as typical signatures of a flux rope that is formed and eventually erupts. Observations of slipping and hot (typically 10 MK) flare loops with their footpoints moving along J-shaped EUV ribbons have been reported (Dudík et al 2014(Dudík et al , 2016Li & Zhang 2014Gou et al 2016), and narrow photospheric current ribbons have been measured along the latter (Aulanier et al 2012;Janvier et al 2014Janvier et al , 2016. These observations are consistent with flux-rope related quasi-separatrix layers (QSLs), and with QSL reconnection (Savcheva et al 2015.…”

Relationships between Photospheric Vertical Electric Currents and Hard X-Ray Sources in Solar Flares: Statistical Study

“…is possible variations of PVECs on time scales of the flare impulsive phase of less than 10 min. Such variations have indeed been found in several flares(Tan et al 2006;Janvier et al 2014;Musset et al 2015;Janvier et al 2016;Sharykin et al 2019). Since we used only vector magnetograms obtained immediately before and after the impulsive phase of the flares, we do not know how PVECs changed during the impulsive phase when the HXR sources were observed.…”

QSL Squasher: A Fast Quasi-separatrix Layer Map Calculator

“…The match between the shapes of QSLs and flare ribbons has been achieved recently by Liu et al (2014), Savcheva et al (2015), and Zhao et al (2016). These QSLs have been shown to move together with the flare ribbons in direction perpendicular to the polarity inversion line (PIL) (Savcheva et al 2016b;Janvier et al 2016).…”

“…The QSLs derived in Savcheva et al (2016b) and Janvier et al (2016) have been derived based on NLFFFs constrained only by pre-flare observations (magnetograms, and EUV and X-ray images), but have managed to reproduce the flaring topology and its evolution to a large extent. That indicates that these kinds of studies have potential predictive power as the use of topology analysis can show us the likely sites of flare reconnection a few hours before the event, as shown in Savcheva et al (2012a).…”

“…The global topology of active regions before eruption has been shown to be important for the characteristics of the dynamics, be it an eruption or just loop reconfiguration (Janvier et al 2016;Jiang et al 2016;Pontin et al 2016;Chintzoglou et al 2016).…”