North-South Asymmetries in Earth's Magnetic Field: Effects on High-Latitude Geospace

TL;DR

This paper reviews how North-South asymmetries in Earth's magnetic field influence high-latitude geospace, affecting magnetosphere-ionosphere-thermosphere coupling and various plasma and current phenomena.

Contribution

It identifies and discusses the primary magnetic field asymmetries and their effects on interhemispheric differences in geospace dynamics.

Findings

Differences in magnetic and geographic pole offsets affect coupling.

Magnetic field strength asymmetries influence plasma convection.

Asymmetries impact auroral and ionospheric phenomena.

Abstract

The solar-wind magnetosphere interaction primarily occurs at altitudes where the dipole component of Earth's magnetic field is dominating. The disturbances that are created in this interaction propagate along magnetic field lines and interact with the ionosphere-thermosphere system. At ionospheric altitudes, the Earth's field deviates significantly from a dipole. North-South asymmetries in the magnetic field imply that the magnetosphere ionosphere-thermosphere (M-I-T) coupling is different in the two hemispheres. In this paper we review the primary differences in the magnetic field at polar latitudes, and the consequences that these have for the M-I-T coupling. We focus on two interhemispheric differences which are thought to have the strongest effects: 1) A difference in the offset between magnetic and geographic poles in the Northern and Southern Hemispheres, and 2) differences in the magnetic field strength at magnetically conjugate regions. These asymmetries lead to differences in plasma convection, neutral winds, total electron content, ion outflow, ionospheric currents and auroral precipitation.