Geomagnetic Field Dynamics During Excursions and Reversals

The geomagnetic field undergoes both long-term and short-term deviations from its predominantly dipolar configuration, expressed as polarity reversals and geomagnetic excursions. These episodes are characterized by significant drops in field intensity and an increase in the paleosecular variation index (PSV index), reflecting changes in the underlying geodynamo. This work focuses on analysing the temporal evolution of the field during these events in order to better constrain the dynamics of the geodynamo.

We utilized some of the most reliable paleomagnetic data-based models such as LSMOD.2, GGFSS70, GGFMB and PADM2M, encompassing different time periods to analyse the rate of change in the dipole moment and the PSV index. A sawtooth pattern of gradual dipole decay followed by rapid recovery during reversals, as proposed by past studies, has been observed in our study on the Matuyama Brunhes reversal. But, in contrast, we observed an opposite behavior of fast decay and slow recovery during most of the excursions. Accordingly, the PSV index exhibited a slow growth–fast recovery pattern during the reversal and a fast decay–slow recovery pattern during many excursions, although the PSV index results vary more than the dipole moment results. In this study, we test whether similar or distinct asymmetries characterize the Gauss–Matuyama reversal. The preliminary outputs from the newly developing Gauss–Matuyama field model were made use for that. Here, we will report the results of this ongoing work.