Flaring Rates and the Evolution of Sunspot Group McIntosh Classifications

TL;DR

This study statistically analyzes how sunspot group evolution in the McIntosh classification correlates with solar flare rates, revealing that upward evolution and increased complexity significantly raise flare likelihood and magnitude.

Contribution

It is the first to examine the statistical relationship between sunspot-group evolution in the McIntosh scheme and solar flaring activity.

Findings

Higher flaring rates are associated with upward evolution in McIntosh classes.

More complex sunspot groups produce higher flare rates regardless of evolution.

Upward evolution from larger classes significantly increases flare likelihood.

Abstract

Sunspot groups are the main source of solar flares, with the energy to power them being supplied by magnetic-field evolution (e.g. flux emergence or twisting/shearing). To date, few studies have investigated the statistical relation between sunspot-group evolution and flaring, with none considering evolution in the McIntosh classification scheme. Here we present a statistical analysis of sunspot groups from Solar Cycle 22, focusing on 24-hour changes in the three McIntosh classification components. Evolution-dependent >C1.0, >M1.0, and >X1.0 flaring rates are calculated, leading to the following results: (i) flaring rates become increasingly higher for greater degrees of upward evolution through the McIntosh classes, with the opposite found for downward evolution; (ii) the highest flaring rates are found for upward evolution from larger, more complex, classes (e.g. Zurich D- and E-classes evolving upward to F-class produce >C1.0 rates of 2.66 +/- 0.28 and 2.31 +/- 0.09 flares per 24 hours, respectively); (iii) increasingly complex classes give higher rates for all flare magnitudes, even when sunspot groups do not evolve over 24 hours. These results support the hypothesis that injection of magnetic energy by flux emergence (i.e. increasing in Zurich or compactness classes) leads to a higher frequency and magnitude of flaring.