Evaluation of Applicability of a Flare Trigger Model based on Comparison of Geometric Structures

TL;DR

This study evaluates a theoretical solar flare-trigger model based on magnetic field geometries against observations of 32 flares, finding it applicable to about 30% of cases and highlighting the importance of specific magnetic configurations.

Contribution

The paper tests and confirms the applicability of a previously proposed MHD-based flare-trigger model to real solar flare observations, emphasizing geometric structures.

Findings

Approximately 30% of flares matched the model.

RS type triggers are more common than OP type.

No observed events contradict the model.

Abstract

The triggering mechanism(s) and critical condition(s) of solar flares are still not completely clarified, although various studies have attempted to elucidate them. We have also proposed a theoretical flare-trigger model based on MHD simulations Kusano et al. 2012, in which two types of small-scale bipole field, the so-called Opposite Polarity (OP) and Reversed Shear (RS) types of field, can trigger flares. In this study, we evaluated the applicability of our flare-trigger model to observation of 32 flares that were observed by the Solar Dynamics Observatory (SDO), by focusing on geometrical structures. We classified the events into six types, including the OP and RS types, based on photospheric magnetic field configuration, presence of precursor brightenings, and shape of the initial flare ribbons. As a result, we found that approximately 30% of the flares were consistent with our flare-trigger model, and the number of RS type triggered flares is larger than that of the OP type. We found none of the sampled events contradicts our flare model, although we cannot clearly determine the trigger mechanism of 70% of the flares in this study. We carefully investigated the applicability of our flare-trigger model and the possibility that other models can explain the other 70% of the events. Consequently, we concluded that our flare-trigger model has certainly proposed important conditions for flare-triggering.