Clustering of Polarity Reversals of the Geomagnetic Field

Often in nature the temporal distribution of inhomogeneous stochastic point processes can be modeled
as a realization of renewal Poisson processes with a variable rate. Here we investigate one of the classical
examples, namely, the temporal distribution of polarity reversals of the geomagnetic field. In spite of the
commonly used underlying hypothesis, we show that this process strongly departs from a Poisson
statistics, the origin of this failure stemming from the presence of temporal clustering. We find that a
Levy statistics is able to reproduce paleomagnetic data, thus suggesting the presence of long-range
correlations in the underlying dynamo process.