Investigation on the Predictive Potentiality of Photospheric Magnetic Parameters for Distinguishing Confined from Eruptive Solar Flares

TL;DR

This study evaluates pre-flare magnetic parameters from active regions to predict whether solar flares will be confined or eruptive, highlighting key parameters like magnetic flux, shear angle, free energy, and polarity centroid distance.

Contribution

It identifies the most relevant magnetic parameters for distinguishing confined from eruptive flares and demonstrates their combined effectiveness in prediction.

Findings

Total unsigned magnetic flux and free magnetic energy are key predictors.

Confined flares tend to have larger high-energy region areas.

The interplay between overlying flux and core flux influences flare eruptiveness.

Abstract

A question often arises as to why some solar flares are confined in the lower corona while others, termed eruptive flares, are associated with coronal mass ejections (CMEs). Here we intend to rank the importance of pre-flare magnetic parameters of active regions in their potentiality to predict whether an imminent flare will be eruptive or confined. We compiled a dataset comprising 277 solar flares of GOES-class M1.0 and above, taking place within 45 deg from the disk center between 2010 and 2023, involving 94 active regions. Among the 277 flares, 135 are confined and 142 are eruptive. Our statistical analysis reveals that the magnetic parameters that are most relevant to the flare category are: total unsigned magnetic flux $\Phi$, mean magnetic shear angle $\Theta$ along the polarity inversion line (PIL), photospheric free magnetic energy $E_f$, and centroid distance $d$ between opposite polarities. These four parameters are not independent of each other, but in combination, might be promising in distinguishing confined from eruptive flares. For a subset of 77 flares with high-gradient PILs, the area of high free energy regions ($A_{\mathrm{Hi}}$) becomes the most effective parameter related to the flare type, with confined flares possessing larger $A_{\mathrm{Hi}}$ than eruptive ones. Our results corroborate the general concept that the eruptive behavior of solar flares is regulated by an interplay between the constraining overlying flux, which is often dominant in both $\Phi$ and $E_f$ and related to $d$, and the current-carrying core flux, which is related to $\Theta$.