Using Extreme Value Theory for Determining the Probability of Carrington-Like Solar Flares

TL;DR

This paper applies extreme value theory to solar flare data to estimate the probabilities of rare, high-impact space weather events like Carrington-like flares, providing more accurate risk assessments.

Contribution

It introduces EVT for solar flare probability estimation, improving upon power law assumptions and aligning results with Kepler data.

Findings

150-year return level is approximately X60 flare

Carrington-like flare is a 1-in-100-year event

EVT results align with Kepler space telescope data

Abstract

Space weather events can negatively affect satellites, the electricity grid, satellite navigation systems and human health. As a consequence, extreme space weather has been added to the UK and other national risk registers. By their very nature, extreme space weather events occur rarely and, therefore, statistical methods are required to determine the probability of their occurrence. Space weather events can be characterised by a number of natural phenomena such as X-ray (solar) flares, solar energetic particle (SEP) fluxes, coronal mass ejections and various geophysical indices (Dst, Kp, F10.7). In this paper extreme value theory (EVT) is used to investigate the probability of extreme solar flares. Previous work has assumed that the distribution of solar flares follows a power law. However such an approach can lead to a poor estimation of the return times of such events due to uncertainties in the tails of the probability distribution function. Using EVT and GOES X-ray flux data it is shown that the expected 150-year return level is approximately an X60 flare whilst a Carrington-like flare is a one in a 100-year event. It is also shown that the EVT results are consistent with flare data from the Kepler space telescope mission.