The magnetic field topology associated to two M flares

TL;DR

This study analyzes the magnetic field topology associated with two confined M-class solar flares, revealing that a stable coronal null point facilitated magnetic reconnection, which explains the energy release during these homologous events.

Contribution

The paper demonstrates that stable coronal null points can serve as sites for magnetic reconnection in confined solar flares, supported by combined observational data and magnetic field modeling.

Findings

Both flares occurred at the same magnetic null point.

The null point remained stable over at least one day.

Magnetic reconnection at the null point explains the energy release.

Abstract

On 27 October, 2003, two GOES M-class flares occurred in the lapse of three hours in active region NOAA 10486. The two flares were confined and their associated brightenings appeared at the same location, displaying a very similar shape both at the chromospheric and coronal levels. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (HASTA, Kanzelhoehe Solar Observatory, TRACE) and coronal (TRACE) observations. By combining our data analysis with a model of the coronal magnetic field, we compute the magnetic field topology associated to the two M flares. We find that both events can be explained in terms of a localized magnetic reconnection process occurring at a coronal magnetic null point. This null point is also present at the same location one day later, on 28 October, 2003. Magnetic energy release at this null point was proposed as the origin of a localized event that occurred independently with a large X17 flare on 28 October, 2003, at 11:01 UT. The three events, those on 27 October and the one on 28 October, are homologous. Our results show that coronal null points can be stable topological structures where energy release via magnetic reconnection can happen, as proposed by classical magnetic reconnection models.