Interaction of the solar wind with a planetary ionosphere

An electrodynamic model for an ionosphere-solar wind interaction is developed based on the existence of a low beta plasma below the anemopause. The currents for the interaction are driven by the solar wind motional electric field and induce a stagnation magnetic field at the anemopause. For Venus and Mars the lower region of the ionosphere near the electron density peak has the highest conductivity, and therefore the tangential component of the induction current flows substantially in this region. The current paths close in the anemopause, which is a solar wind current sheath analogous to the magnetopause. Both the fraction of the undisturbed solar wind motional electric field, which drives the induction current, and the required fraction of incident solar wind particles, crossing the anemopause to produce this current, are shown to be small