The Terrestrial Magnetosphere

Abstract

A magnetosphere is shaped by the interaction between a planetary magnetic field and the solar wind. The magnetopause is a discontinuity separating both fields, forming a cavity in the solar wind. Since the solar wind is a supersonic flow, a standing shock wave, the bow shock, develops in front of the magnetopause. In the anti-sunward direction, the magnetosphere is stretched by the solar wind, forming the magnetotail. Inside the magnetosphere, different plasma regimes exist, dominated by ionospheric plasma in the plasmasphere, a highly variable mixture of ionospheric and heliospheric plasma in the geosphere, and by the solar wind plasma in the outer magnetosphere. These different regimes are coupled by fields and currents. Inside the plasmasphere energetic particles are trapped in the radiation belts. The inner magnetosphere can be approximated as a slightly distorted dipole field. It is coupled to the ionospheric current system, with energy in the form of particles and waves exchanged between both regimes. Both ionospheric currents and the ring current associated with the radiation belt particles modify the dipole field.

The poet’s eye, in a fine frenzy rolling, Doth glance from Heaven to Earth, from Earth to Heaven, and, as imagination bodies forth the forms of things unknown, the poet’s pen turns them to shapes, and gives airy nothing a local habitation and a name.

W. Shakespeare, Much Ado About Nothing