Severe Ionosphere magnetic storms are feared events for integrity andcontinuity of navigation systems such as EGNOS, the European SBAS(Satellite-Based Augmentation System) complementing GPS and an accuratemodelling of this event probability is necessary. Our aim for the workpresented in this paper is to give an estimation of the frequency of suchextreme magnetic storms per time unit (year) throughout a solar cycle. Thus, wedevelop an innovative approach based on a proportional hazard model, inspiredby the Cox model, with time dependent covariates. The number of storms during acycle is supposed to be a non-homogeneous Poisson process. The intensity ofthis process could be expressed as the product of a baseline risk and a riskfactor. Contrary to what is done in the Cox model, the baseline risk is oneparameter of interest (and not a nuisance one), it is the intensity toestimate. As in Extreme Value Theory, all the high level events will be used tomake estimation and the results will be extrapolated to the extreme level ones.After a precise description of the model, we present the estimation results anda model extension. A prediction for the current solar cycle (24th) is alsoproposed.
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