Interaction of the Solar Wind with Unmagnetized Planets

Abstract

The results of a one-dimensional electromagnetic hybrid simulation of the interaction between the ionospheres of Venus and Mars and the solar wind are presented. Finite electron inertia is retained, allowing for the analysis of the lower hybrid waves propagating along an oblique but fixed angle to the shocked solar-wind magnetic field. The waves are excited by a relative drift between a cold electron beam, created by $\mathbf{E}\ifmmode\times\else\texttimes\fi{}\mathbf{B}$ pickup, and the planetary oxygen ions. The free energy source for instability is in the solar-wind proton flow supporting electron drift through the convective electric field. The waves generate a collective friction between the shocked solar-wind flow and planetary ions.