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The distribution and direction of extreme geomagnetic fluctuations over 1-60 minute periods

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Abstract

We present a statistical climatological study of extreme fluctuations in the horizontal geomagnetic field (dB/dt), generated at the Earth’s surface by extreme electrical currents in the ionosphere and magnetosphere. Applying techniques from Extreme Value Theory we predict the magnitude of |dB/dt| for return periods (RP) from 5 to 500 years. Results presented for both ramp changes and RMS variations over periods from 1–60 minutes show considerable variation in magnitude and rate of occurrence when considered as functions of magnetic latitude, local time, and season. The direction of extreme geomagnetic fluctuations is strongly isotropic at lower latitudes, but this changes with timescale. A technique for improving return level estimates by combining Generalised Pareto tail distributions from discrete directional sectors produces return levels that are higher at low geomagnetic latitudes but higher at mid to high latitudes.

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©2020 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Due to the COVID-19 pandemic, the URSI Board, together with the GASS 2020 Local Organizing Committee decided to postpone the URSI 2020 General Assembly and Scientific Symposium by 1 year. However, all authors of accepted papers were offered the possibility to either withdrawn their paper or to publish their work in the GASS 2020 Proceedings.