Statistics of Solar White-Light Flares I: Optimization of Identification Methods and Application

TL;DR

This study improves the identification of solar white-light flares using optimized methods, leading to a higher detection rate and revealing statistical relationships between flare energy and duration, thus enhancing understanding of solar and stellar flare phenomena.

Contribution

The paper introduces a novel identification method for solar WLFs that increases detection rates and enables more comprehensive statistical analysis.

Findings

Identified 55 WLFs out of 90 flares, with a 30% detection rate for C-class flares.

Higher WLF proportion in confined flares compared to eruptive flares at each energy level.

Discovered a power-law relation between WLF energy and duration: τ ∝ E^0.22.

Abstract

White-light flares (WLFs) are energetic activity in stellar atmosphere. However, the observed solar WLF is relatively rare compared to stellar WLFs or solar flares observed at other wavelengths, limiting our further understanding solar/stellar WLFs through statistical studies. By analyzing flare observations from the \emph{Solar Dynamics Observatory (SDO)}, here we improve WLF identification methods for obtaining more solar WLFs and their accurate light curves from two aspects: 1) imposing constraints defined by the typical temporal and spatial distribution characteristics of WLF-induced signals; 2) setting the intrinsic threshold for each pixel in the flare ribbon region according to its inherent background fluctuation rather than a fixed threshold for the whole region. Applying the optimized method to 90 flares (30 C-class ones, 30 M-class ones, and 30 X-class ones) for a statistical study, we identified a total of 9 C-class WLFs, 18 M-class WLFs, and 28 X-class WLFs. The WLF identification rate of C-class flares reported here reaches 30\%, which is the highest to date to our best knowledge. It is also revealed that in each GOES energy level, the proportion of WLFs is higher in confined flares than that in eruptive flares. Moreover, a power-law relation is found between the WLF energy (\emph{E}) and duration ($\tau$): $\tau \propto {E}^{0.22}$, similar to those of solar hard/soft X-ray flares and other stellar WLFs. These results indicate that we could recognize more solar WLFs through optimizing the identification method, which will lay a base for future statistical and comparison study of solar and stellar WLFs.