Some possible evidence for a chaotic geomagnetic field from observational data

The behaviour of the geomagnetic field as observed almost continuously at three European locations over the last 130 years is investigated by means of a non-linear forecasting approach. The analysis of the data in terms of first-differences
(secular variation) of the horizontal magnetic components made in phase space with the simplex technique seems to exclude
the pre-eminence of any stochastic or periodic behaviour. The dimensionality of the underlying non-linear process and the
corresponding largest positive Lyapunov exponent are estimated. The results give some evidence that the geomagnetic field evolves as a non-linear chaotic system with unpredictable behaviour after times greater than a few years, confirming the common practice of updating global models of the geomagnetic field every 5 years.

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