Relationship between non-thermal electron energy spectra and GOES classes

TL;DR

This study shows that the GOES class of solar flares is significantly affected by the spectral index and low energy cut-off of non-thermal electron distributions, not just total electron energy.

Contribution

It demonstrates how variations in electron energy spectra influence the classification of solar flares, providing a new understanding of flare energetics and classification.

Findings

Changing electron spectral parameters alters GOES class significantly.

A M2.7 flare can be reclassified as C1.4 by spectral variation.

Correlation between HXR and SXR fluxes depends on HXR energy range.

Abstract

We investigate the influence of the variations of energy spectrum of non-thermal electrons on the resulting GOES classes of solar flares. Twelve observed flares with various soft to hard X-ray emission ratios were modelled using different non-thermal electron energy distributions. Initial values of the flare physical parameters including geometrical properties were estimated using observations. We found that, for a fixed total energy of non-thermal electrons in a flare, the resulting GOES class of the flare can be changed significantly by varying the spectral index and low energy cut-off of the non-thermal electron distribution. Thus, the GOES class of a flare depends not only on the total non-thermal electrons energy but also on the electron beam parameters. For example, we were able to convert a M2.7 class solar flare into a merely C1.4 class one and a B8.1 class event into a C2.6 class flare. The results of our work also suggest that the level of correlation between the cumulative time integral of HXR and SXR fluxes can depend on the considered HXR energy range.