Active region and flare ribbon properties associated with X-class flares and CMEs of solar cycle 24

Abstract

The solar eruptive events and their origin are important in the context of forecasting their occurrence and their effects on the space and the earth. In this paper, a set of 45 X-class flare-associated coronal mass ejections (CMEs) and their source region characteristics are analysed. The X-ray flares and white light CMEs were observed by GOES and SOHO/LASCO, respectively during 2011 – 2015 in solar cycle 24. First, a preliminary analysis of their properties and relations between them is made. The CMEs in the present sample are fast (mean speed ∼1095 km/s), highly decelerating (mean a = ‑45 m/s²) and consists of 50% (22/40) of halo CMEs. Weak correlation is obtained from 0.27 to 0.36 between flare strength and CME properties. Secondly, the properties of the solar source region (sunspot classification according to Hale and McIntosh, sunspot area and the number of sunspots) and active region/flare ribbon (total unsigned magnetic flux, ribbon reconnection flux, active region area, ribbon area, and the ratio of ribbon to active region properties) are obtained for a subset of events and they are analysed to find the dependence of the flare/CME properties with the source region characteristics. It is found that many of the X-class flares were produced by βϒδ Hale-type sunspot group and Fkc/Ekc/Dkc McIntosh sunspot class. The flare strength/CME speed is found to be correlated better with the flare ribbon properties (like reconnection flux and area) than the active region properties. In addition, the flare strength/CME speeds are compared with the SHARP parameters and we found moderate correlations between the flare strength/CME speed with SHARP parameters. The above results of X-class flare associated events are discussed in comparison and in contrast with others published for other sets of events.