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 common 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 temporal clustering, thus suggesting the presence of long-range correlations in the underlying dynamo process. In this framework we compare our results with the behaviour of different models that describe the time evolution of the reversals.