Statistical Study of Solar White-light Flares and Comparison with Superflares on Solar-type Stars

TL;DR

This study analyzes 50 solar white-light flares to compare their energy-duration relation with stellar superflares, revealing similar scaling but longer durations on the Sun, and discusses possible physical explanations based on magnetic reconnection and cooling timescales.

Contribution

It provides the first detailed statistical comparison of solar white-light flares with stellar superflares, highlighting similarities and differences in their energy-duration relations.

Findings

Solar WLFs follow a t∝E^{0.38} relation similar to superflares

Durations of stellar superflares are shorter than solar extrapolations

Cooling timescales may influence decay times in solar flares

Abstract

Recently, many superflares on solar-type stars were discovered as white-light flares (WLFs). A correlation between the energies (E) and durations (t) of superflares is derived as $t\propto E^{0.39}$, and this can be theoretically explained by magnetic reconnection ($t\propto E^{1/3}$). In this study, we carried out a statistical research on 50 solar WLFs with SDO/HMI to examine the t-E relation. As a result, the t-E relation on solar WLFs ($t\propto E^{0.38}$) is quite similar stellar superflares, but the durations of stellar superflares are much shorter than those extrapolated from solar WLFs. We present the following two interpretations; (1) in solar flares, the cooling timescale of WL emission may be longer than the reconnection one, and the decay time can be determined by the cooling timescale; (2) the distribution can be understood by applying a scaling law $t\propto E^{1/3}B^{-5/3}$ derived from the magnetic reconnection theory.