Energy Partition in Four Confined Circular-Ribbon Flares

TL;DR

This study analyzes the energy distribution in four confined circular-ribbon solar flares, revealing how energy components scale with flare size and distinguishing features from eruptive flares, with implications for space weather prediction.

Contribution

It provides the first detailed energy partition analysis of confined circular-ribbon flares, highlighting the higher nonthermal to magnetic energy ratio compared to eruptive flares.

Findings

Energy components increase with flare class.

Magnetic free energy exceeds other energy components.

Higher nonthermal to magnetic energy ratio distinguishes confined flares.

Abstract

In this study, we investigated the energy partition of four confined circular-ribbon flares (CRFs) near the solar disk center, which are observed simultaneously by SDO, GOES, and RHESSI. We calculated different energy components, including the radiative outputs in 1$-$8, 1$-$70, and 70$-$370 {\AA}, total radiative loss, peak thermal energy derived from GOES and RHESSI, nonthermal energy in flare-accelerated electrons, and magnetic free energy before flares. It is found that the energy components increase systematically with the flare class, indicating that more energies are involved in larger flares. The magnetic free energies are larger than the nonthermal energies and radiative outputs of flares, which is consistent with the magnetic nature of flares. The ratio $\frac{E_{nth}}{E_{mag}}$ of the four flares, being 0.70$-$0.76, is considerably higher than that of eruptive flares. Hence, this ratio may serve as an important factor that discriminates confined and eruptive flares. The nonthermal energies are sufficient to provide the heating requirements including the peak thermal energy and radiative loss. Our findings impose constraint on theoretical models of confined CRFs and have potential implication for the space weather forecast.