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.
Sandra Chapman is the 2023 ISSI Johannes Geiss Fellow. She is primarily but not exclusively a plasma physicist working on non-linear and complex systems in astrophysics and in the laboratory. She is Professor of Physics and founding Director of the Centre for Fusion, Space and Astrophysics at the University of Warwick, UK and Adjunct Professor at the University of Tromso. She read Physics on an Exhibition Scholarship to Imperial College, London and her interest in nonlinear systems began with her PhD work (also Imperial College). Her early work was recognised with the COSPAR Zeldovich Medal (commission D) and the EGS Young Scientists’ Medal. Awards include the 2014 RAS James Dungey Lecture, the 2020 AGU Ed Lorenz Lecture, a 2021 Lloyd’s of London Science of Risk Prize, and the 2022 RAS Chapman Medal. Sandra was a 2017/18 Fulbright-Lloyd’s of London Scholar and a 2003/4 Fellow at the Radcliffe Institute for Advanced Study, Harvard.
Webinar was recorded on February 23, 2023