Starship Asterisk*

Multiple cycles of the irregular, but roughly 11 year cycle of solar and geomagnetic activity is mapped onto a regular solar cycle clock with increasing time read clockwise. Credit: S. C. Chapman et al, 2020 GRL

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Extreme space weather events can significantly impact systems such as satellites, communications systems, power distribution and aviation. They are driven by solar activity which is known to have an irregular but roughly 11 year cycle. By devising a new, regular ‘sun clock’, researchers have found that the switch on and off of periods of high solar activity is quite sharp, and are able to determine the switch on/off times. Their analysis shows that whilst extreme events can happen at any time, they are much less likely to occur in the quiet interval.

The clock will help scientists to determine more precisely when the risk for solar storms is highest and help to plan the impacts of space weather on our space infrastructure, important since the next switch on of activity may be imminent as solar activity moves from its current minimum.

... the sun clock uses the daily sunspot number record available since 1818 to map solar activity over 18 solar cycles to a standardised 11 year cycle or ‘clock’. No two solar cycles are the same, but using a mathematical technique known as the Hilbert transform, the researchers were able to standardise the solar activity cycle for the first time. ...

• Geophysical Research Letters 47(11):e2020GL087795 (16 Jun 2020) DOI: 10.1029/2020GL087795