Statistical Characteristics of Active Regions and Flare Ribbons Associated with Large Flares

Abstract

We present the results of a statistical study of the characteristics of active regions (ARs) and ribbons associated with flares of GOES class M5.0 and larger, occurring from February 2011 to December 2022 within 40° of the central meridian. A total of 60 flares met these criteria, of which 39 were eruptive and 21 confined. We used SDO/HMI and SDO/AIA data to obtain the magnetic reconnection fluxes and rates. Magnetic reconnection fluxes and ribbon areas of confined and eruptive flares correlate with the flares GOES class. For flares of the same GOES class in confined events, compared to eruptive ones, the mean magnetic flux density in the ribbon is higher. Reconnection rates in confined and eruptive flares showed a temporal evolution similar to observed hard X-ray (HXR) emission. The fraction of AR involved in reconnection is larger in eruptive flares and for both types of events it decreases with increasing distance between the flare and the AR center. For the same fraction of AR involved in the flare, eruptive events, compared to confined ones, are located at distances twice as far from the AR center. Eruptive flares tend to occur in compact ARs at the periphery, while confined ones occur in extended ARs near the center.