Characterising Solar Magnetic Reconnection in Confined and Eruptive Flares

Abstract

Magnetic reconnection is a fundamental mechanism through which energy stored in magnetic fields is released explosively on a massive scale, they could be presented as eruptive or confined flares, depending on their association with coronal mass ejections (CMEs). Several previous works have concluded that there is no correlation between flare duration and flare class, however, their sample sizes are skewed towards B and C classes; they hardly represent the higher classes. Therefore, we studied a sample without extreme events in order to determine the correlation between flare duration and flare type (confined and eruptive). We examined $33$ flares with classes between M5 to X5 within $45^{\circ}$ of the disk centres, using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI). We find that the linear correlation between flare class against flare duration by full width half maximum (FWHM) in general is weak ($r=0.19$); however, confined flares have a significant correlation ($r=0.58$) compared to eruptive types ($r=0.08$). Also, the confined M class flares' average duration is less than half of the eruptive flares. Similarly, confined flares have a higher correlation ($r=0.89$) than eruptive flares ($r=0.60$) between flare classes against magnetic reconnection flux. In this work, a balanced sample size between flare types is an important strategy for obtaining a reliable quantitative comparison.