Motions in the magnetosphere of the Earth

Abstract

The conditions determining the dynamical behavior of the ionized gas in the outer atmosphere of the earth are discussed. It is proposed to call this region in which the magnetic field of the earth dominates the ‘magnetosphere.’ Observations by Van Allen and others indicate that this zone reaches out to between 5 and 10 earth radii, depending on the degree of magnetic disturbance. It is shown that the existence of an insulating layer at the base of this region, namely the non-ionized atmosphere, completely changes the type of control exerted by the magnetic field, allowing a class of motions to occur freely without the need to overcome any magnetic forces. The extent to which such motions may occur is discussed, and some of the indications from airglow and magnetic observations are mentioned. The theory predicts that, at the level of the F2 layer and above, most motions will show strict symmetry between the two base points of a magnetic line of force.