A statistical analysis of polarity reversals of the geomagnetic field

We investigate the temporal distribution of polarity reversals of the geomagnetic field. In spite of the commonly assumption that the reversal sequence can be modeled as a realization of a renewal Poisson process with a variable rate, we show that the polarity reversals strongly depart from a local Poisson statistics. The origin of this failure can be attributed to the presence of temporal clustering. We also show that a Lévy function is able to reproduce the distribution of polarity persistence times, thus suggesting the presence of long-range correlations in the underlying dynamo process. In this framework we compare our results with the behavior of some toy models that describe the time evolution of the reversals and with MHD geodynamo numerical simulations.