Energy partition in two M-class circular-ribbon flares

Abstract

In this paper, we investigate the energy partition of two homologous M1.1 circular-ribbon flares (CRFs) in active region (AR) 12434. They were observed by \textit{SDO}, \textit{GOES}, and \textit{RHESSI} on 2015 October 15 and 16, respectively. The peak thermal energy, nonthermal energy of flare-accelerated electrons, total radiative loss of hot plasma, and radiant energies in 1$-$8 Å and 1$-$70 Å of the flares are calculated. The two flares have similar energetics. The peak thermal energies are (1.94$\pm$0.13)$\times$10${}^{30}$ erg. The nonthermal energies in flare-accelerated electrons are (3.9$\pm$0.7)$\times$10${}^{30}$ erg. The radiative outputs of the flare loops in 1$-$70 Å, which are $\sim$200 times greater than the outputs in 1$-$8 Å, account for $\sim$62.5\% of the peak thermal energies. The radiative losses of SXR-emitting plasma are one order of magnitude lower than the peak thermal energies. Therefore, the total heating requirements of flare loops including radiative loss are (2.1$\pm$0.1)$\times$10${}^{30}$ erg, which could sufficiently be supplied by nonthermal electrons.

17 pages, 12 figures, accepted by ApJ