  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.
