Scene Setting Talk on Comparative Solar Minima

Campaigns during the last two solar minima – Whole Heliosphere Interval (WHI) in SC 23-24 and Whole Sun Month (WSM) in SC 22-23 – had the unexpected result of demonstrating that all solar minima are not alike. Rather than being simply intervals of low solar activity separating active solar maximum intervals, they had interesting phenomenological differences that translated into changes in the geospace response. Differences in the Sun’s magnetic field structure, in particular, the distribution and evolution of coronal holes played a major role. Sunspot number, which is used to track the progression of the solar cycle, is not a good measure of these differences. This presentation will summarize what was learned in the comparison between WSM and WHI, and briefly outline a selection of results from the literature for the present solar minimum that raise questions relevant to the comparative solar-minima theme. The WHPI campaign is an opportunity to continue building knowledge of solar-minimum variability, its sources, and its consequences for the heliosphere and geospace environments, in this case extending to include planetary environments