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Quantifying the solar cycle modulation of extreme space weather

Chapman, S. C., McIntosh, S. W., Leamon, R. J. and Watkins, N. W. (2020) Quantifying the solar cycle modulation of extreme space weather. Geophysical Research Letters, 47 (11). ISSN 0094-8276

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Identification Number: 10.1029/2020GL087795

Abstract

By obtaining the analytic signal of daily sunspot numbers since 1818 we construct a new solar cycle phase clock that maps each of the last 18 solar cycles onto a single normalized 11 year epoch. This clock orders solar coronal activity and extremes of the aa index, which tracks geomagnetic storms at the Earth's surface over the last 14 solar cycles. We identify geomagnetically quiet intervals that are 40% of the normalized cycle, ±2π/5 in phase or ±2.2 years around solar minimum. Since 1868 only two severe (aa>300 nT) and one extreme (aa>500 nT) geomagnetic storms occurred in quiet intervals; 1–3% of severe (aa>300 nT) geomagnetic storms and 4–6% of C-, M-, and X-class solar flares occurred in quiet intervals. This provides quantitative support to planning resilience against space weather impacts since only a few percent of all severe storms occur in quiet intervals and their start and end times are quantifiable.

Item Type: Article
Additional Information: © 2020 The Authors
Divisions: Centre for Analysis of Time Series
Subjects: Q Science > QE Geology
Q Science > Q Science (General)
Date Deposited: 24 Jun 2020 12:06
Last Modified: 15 Jul 2020 11:48
URI: http://eprints.lse.ac.uk/id/eprint/105182

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