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