Earth’s magnetic field has changed its polarity several time in the course of Earth’s history, with magnetic north and south pole changing their positions. The last long-term polarity reversal took place about 780000 years ago. Predominantly stable polarity epochs, that might be interrupted by short so-called magnetic excursions, are named after important geoscientists. The last polarity change is called Matuyama-Brunhes reversal, as the last epoch of inverse polarity is named after Motonori Matuyama, and the current normal polarity epoch after Bernard Brunhes. The existing paleomagnetic data suggest that the geomagnetic field gets very weak during a reversal. Moreover, it loses its dipolar structure, that dominates during stable times, so that small-scale structure with more than two magnetic poles dominates during a polarity change. Details of the reversal processes are not yet understood.

In this project we will compile paleomagnetic data from volcanic rocks and sediment cores, that have been published worldwide over the last decades, in order to develop a global magnetic field model for the Matuyama-Brunhes reversal. Attention has to be paid to quality and independent dating of the paleomagnetic data. The new model will be based on spherical harmonic functions, like present-day geomagnetic field models, and will describe the temporal evolution continuously. It will serve to better understand the processes in Earth’s outer core during a polarity reversal, and also to estimate the reduced magnetic shielding against solar wind and cosmic rays during such an extreme geomagnetic field change.

Time Frame

2021 - 2023

Funding

Alexander von Humboldt-Stiftung

Principal Investigators

• Dr. Ahmed Nasser Mahgoub Ahmed
• Dr. Monika Korte

Cooperations

• Dr. Lennart de Groot (Utrecht University)