Magnetic Flux of Active Regions Determining the Eruptive Character of Large Solar Flares

TL;DR

This study analyzes 322 large solar flares to determine how the magnetic flux of active regions influences whether flares are eruptive or confined, revealing that larger flux regions tend to produce confined flares with fewer associated CMEs.

Contribution

It establishes a quantitative relationship between active region magnetic flux and the eruptive nature of large solar flares, supported by a comprehensive flare database.

Findings

Higher magnetic flux in active regions correlates with fewer CMEs.

Confined flares from large active regions show specific magnetic characteristics.

Active region flux can be used to forecast CME occurrence in large flares.

Abstract

We establish the largest eruptive/confined flare database to date and analyze 322 flares of \emph{GOES} class M1.0 and larger that occurred during 2010$-$2019, i.e., almost spanning the entire solar cycle 24. We find that the total unsigned magnetic flux ($\Phi$$_{AR}$) of active regions (ARs) is a key parameter in governing the eruptive character of large flares, with the proportion of eruptive flares exhibiting a strong anti-correlation with $\Phi$$_{AR}$. This means that an AR containing a large magnetic flux has a lower probability for the large flares it produces to be associated with a coronal mass ejection (CME). This finding is supported by the high positive correlation we obtained between the critical decay index height and $\Phi$$_{AR}$, implying that ARs with a larger $\Phi$$_{AR}$ have a stronger magnetic confinement. Moreover, the confined flares originating from ARs larger than 1.0$\times$$10^{23}$ Mx have several characteristics in common: stable filament, slipping magnetic reconnection and strongly sheared post-flare loops. Our findings reveal new relations between the magnetic flux of ARs and the occurrence of CMEs in association with large flares. These relations obtained here provide quantitative criteria for forecasting CMEs and adverse space weather, and have also important implications for "superflares" on solar-type stars and stellar CMEs. The link of database is https://doi.org/10.12149/101030.