Behaviour of the Geomagnetic Field during Reversals and Excursions

As demonstrated by a three-dimensional geodynamo model, during reversals and excursions of the geomagnetic field, with small amplitudes of heat sources, there occurs attenuation not only of the dipolar magnetic field but also of the high harmonic field. In this scenario, the Earth’s magnetosphere can be significantly smaller than previously expected, and correspondingly, the amount of radiation that penetrates the Earth could be greater.