Webinar with Sandra Chapman (University of Warwick & 2023 Johannes Geiss Fellow)

A Clock for the Solar Cycle Variation of Extreme Space Weather Activity

Extreme geomagnetic storms can have significant impact on a wide range of technologies and a particular challenge is quantifying their occurrence likelihood since they are rare events. Geomagnetic storm occurrence varies with the solar cycle and each cycle has a unique amplitude and duration. Whilst there are comprehensive high fidelity space weather relevant observations over the last four to five solar cycles, observations that extend over multiple cycles are more limited. Nevertheless, historical ground magnetic observations over the last 150 years can be used to quantify space weather risk. They can be combined with the sunspot record to construct a uniform ‘clock’ for space weather activity which reveals a fast switch-on (and off) between the relatively quiet conditions around solar minima, and more active conditions around solar maxima. The clock provides a framework to predict the switch-on and off times, imperative since some of the most extreme events have occurred just after the switch-on.