Atmospheric ionization rates during a geomagnetic reversal

TL;DR

This study models atmospheric ionization rates during the Earth's geomagnetic reversal, revealing significant increases at low latitudes and highlighting the reversal's impact on solar cycle-related ionization variability.

Contribution

It introduces a novel 3D time series model of atmospheric ionization during a geomagnetic reversal based on paleomagnetic data.

Findings

Ionization increases by ~25% at the surface during reversal.

Upper atmosphere ionization increases up to fivefold.

Reversal significantly affects solar cycle-related ionization changes.

Abstract

The Matuyama-Brunhes reversal of Earth's magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn might impact atmospheric ionization rates. In this study a model that yields atmospheric ionization for the entire globe based on an input magnetic field is presented. Taking the time dependent paleomagnetic data as input, a 3D time series of the atmospheric ionization rates during the reversal is produced. We show, that as the dipole field weakens, the atmospheric ionization increases at low latitudes. The increase is ca. 25% at the surface and up to a factor of 5 in the upper atmosphere. Globally, ionization rates increase around 13% at the surface and up to a factor of 2 in the upper atmosphere, whereas polar regions are largely unaffected. Finally, the change in ionization due to the solar 11-year cycle is greatly affected by the reversal. The relative change in atmospheric ionization between solar-minimum and solar-maximum varies between 2 and two orders of magnitude. All atmospheric ionization data is made available for download.