Predicting extremes in European geomagnetic activity

Rapid variations in the geomagnetic field constitute a natural hazard, e.g. for navigation
and to power grids and pipeline networks. In order to better allocate resources
towards mitigating these risks, we must be able to model the recurrence of extremes of
geomagnetic activity over many years.

However, the data we have from which to develop such a model, in the form of continuous
series of 1-minute samples of the geomagnetic field, typically stretch back less
than 40 years. Without a longer record, it is difficult to construct a clear picture of the
magnitude and frequency of extremes in geomagnetic activity.

We therefore apply the statistical technique of ‘extreme value analysis’ on a number of
decades of geomagnetic data recorded at observatories across Europe, and in doing
so arrive at an estimate of the maximum field strength and time-variation that might be
observed once in every 100 and 200 years.