Charting the solar cycle variation of the climate of space weather and its impacts

<p>Sunspot records reveal that whilst the sun has an approximately 11 year cycle of activity, no two cycles are of the same duration. Since this activity is a direct driver of space weather at earth, this presents an operational challenge to quantifying space weather risk. We recently showed [1,2] that the Hilbert transform of the sunspot record can be used to map the variable cycle length onto a regular 'clock' where each cycle has the same duration in Hilbert analytic phase.&#160; Extreme geomagnetic storms rarely occur within the quiet part of the cycle which is a fixed interval of analytic phase on the clock; there is a clear active-quiet switch-off and quiet-active switch-on of activity. Some of the most extreme geomagnetic storms have occurred just at the switch-on time, rather than at solar maximum, so that determining when this will occur could provide guidance on planning and preparedness which necessarily must balance resilience against cost. Here [3] we show how the times of the switch-on/off can be determined directly from the sunspot time-series, without requiring a Hilbert transform.&#160; We propose a method- charting- that can be used to combine observations, and both historical and current reports of societal impacts, to improve our understanding of space weather risk.</p> <p>[1] S. C. Chapman, S. W. McIntosh, R. J. Leamon, N. W. Watkins, Quantifying the solar cycle modulation of extreme space weather, Geophysical Research Letters, (2020) doi:10.1029/2020GL087795</p> <p>[2] S. C. Chapman, S. W. McIntosh, R. J. Leamon, N. W. Watkins, The Sun's magnetic (Hale) cycle and 27 day recurrences in the aa geomagnetic index. Ap. J. (2021) doi: 10.3847/1538-4357/ac069e</p> <p>[3] S. C. Chapman, Charting the Solar Cycle, Front. Astron. Space Sci. - Space Physics, in press (2022) doi<strong>:</strong>&#160;10.3389/fspas.2022.1037096</p>