North–South Asymmetries in Earth’s Magnetic Field

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 ionospherethermosphere system. At ionospheric altitudes, the Earth's field deviates significantly from a dipole. North-South asymmetries in the magnetic field imply that the magnetosphereionosphere-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 asym-KML, SEM, SH, and JPR were supported by the Research Council of Norway/CoE under contract 223252/F50. IC was supported by a fellowship of the Natural Environment Research Council, grant number NE/J018058/1. NP was supported by the U.S. National Science Foundation AGS-1522830. JCC was funded by Natural Environment Research Council (NERC) grant NE/L007177/1. We acknowledge the International Space Science Institute for support for our international team on "Magnetosphere-ionosphere-thermosphere coupling: differences and similarities between the two hemispheres." metries lead to differences in plasma convection, neutral winds, total electron content, ion outflow, ionospheric currents and auroral precipitation.