A paradigmatic model of Earth's magnetic field reversals

TL;DR

This paper presents a mean-field dynamo model explaining Earth's magnetic field reversals, focusing on spectral properties near exceptional points to replicate observed reversal features like timescale and asymmetry.

Contribution

It introduces a simplified dynamo model that attributes reversals to spectral phenomena near exceptional points, providing insights into the reversal mechanism.

Findings

Model reproduces observed reversal timescales.

Explains asymmetry with slow decay and rapid recovery.

Links reversals to spectral coalescence phenomena.

Abstract

The irregular polarity reversals of the Earth's magnetic field have attracted much interest during the last decades. Despite the fact that recent numerical simulations of the geodynamo have shown nice polarity transitions, the very reason and the basic mechanism of reversals are far from being understood. Using a paradigmatic mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha we attribute the essential features of reversals to the magnetic field dynamics in the vicinity of an exceptional point of the spectrum of the non-selfadjoint dynamo operator. At such exceptional (branch) points of square root type two real eigenvalues coalesce and continue as a complex conjugated pair of eigenvalues. Special focus is laid on the comparison of numerically computed time series with paleomagnetic observations. It is shown that the considered dynamo model with high supercriticality can explain the observed time scale and the asymmetric shape of reversals with a slow decay and a fast field recovery.