The Confined X-class Flares of Solar Active Region 2192

TL;DR

This paper analyzes the unique confined X-class flares of solar active region 2192, revealing repeated energy release, magnetic confinement effects, and detailed electron acceleration characteristics, highlighting the region's exceptional flare productivity without CMEs.

Contribution

It provides a detailed analysis of the confined X1.6 flare in active region 2192, demonstrating repeated magnetic reconnection and quantifying electron acceleration and energy release in a highly confined solar flare.

Findings

Recurrent magnetic reconnection involving the same structures.

High non-thermal energy in electrons, about 10% of magnetic energy.

Flare confinement due to large-scale magnetic arcade fields.

Abstract

The unusually large NOAA active region 2192, observed in October 2014, was outstanding in its productivity of major two-ribbon flares without coronal mass ejections. On a large scale, a predominantly north-south oriented magnetic system of arcade fields served as a strong, also lateral, confinement for a series of large two-ribbon flares originating from the core of the active region. The large initial separation of the flare ribbons, together with an almost absent growth in ribbon separation, suggests a confined reconnection site high up in the corona. Based on a detailed analysis of the confined X1.6 flare on October 22, we show how exceptional the flaring of this active region was. We provide evidence for repeated energy release, indicating that the same magnetic field structures were repeatedly involved in magnetic reconnection. We find that a large number of electrons was accelerated to non-thermal energies, revealing a steep power law spectrum, but that only a small fraction was accelerated to high energies. The total non-thermal energy in electrons derived (on the order of 10^25 J) is considerably higher than that in eruptive flares of class X1, and corresponds to about 10\% of the excess magnetic energy present in the active-region corona.