On longitudinal currents in the magnetosphere.

A general formula is derived relating the density of the vertical currents in the ionosphere to the distribution of the isotropic pressure in the magnetosphere under conditions of magnetohydrostatic equilibrium. It is shown that the most probable region for the formation of field-aligned currents on the nightside is that of the transition from a low to a high plasma pressure. Attention is also given to the applicability of a model having isotropic pressure to the case of small-scale disturbances in the electrostatic potential of the magnetosphere.