Study of Long-Duration Flares and Associated Chromospheric and Coronal Ejections in Solar Cycles 23 and 24

Abstract

A statistical study of long-duration (long-duration event, LDE) flares in the soft X-ray (SXR) range for solar cycles 23 and 24 is carried out. Graphs of the dependence of the strength of LDE flares and coronal mass ejections (CMEs) on the duration of these flares are constructed. As a result, we find that a significant proportion of LDE flares is not associated with large mass CMEs. This contradicts the hypothesis that the energy required to maintain the post-eruptive phase of LDE flares is supplied by the energy of settling matter after CME eruption. However, most flares are accompanied by mini-eruptions, which may have a significance in the energy balance of LDEs. The diagram of the strength–duration of flares shows that there is a limit of energy and maximum strength of an LDE flare in the SXR range in LDE events. Apparently, this limit differs for cycles 23 and 24. This fact may indicate that there is a limit to the maximum flare energy that can be observed in a particular solar cycle.