Rates of Geomagnetic Field Change During Excursions and Reversals

Abstract

The Earth's magnetic field is characterized by complex changes, reflecting various geodynamo processes. Paleomagnetic studies have provided evidence of geomagnetic polarity reversals and excursions throughout Earth's history. We use data‐based paleomagnetic field models (LSMOD.2, GGFSS70, and GGFMB) and the axial dipole moment reconstruction PADM2M, which spans multiple excursions and a reversal, to analyze the field characteristics during these extreme variations. In particular we study the asymmetry in rates of change of dipole moment and paleo‐secular variation (PSV) index during different events. A sawtooth pattern of gradual dipole decay followed by rapid recovery during reversals, as proposed by earlier studies, is observed in our analysis of the Matuyama–Brunhes reversal. In contrast, we observed an opposite behavior of fast dipole decay and slow recovery during most of the studied excursions, suggesting the possibility that excursions may be governed by a mechanism distinct from that of reversals. Although less pronounced than in the dipole moment, the PSV index also exhibits an opposite asymmetric pattern during excursions and reversals.