Ion cooling in collisionless plasma expansion.

Abstract

The ion cooling in collisionless plasma expansion is revisited. It is shown that, in the case of an initial Maxwellian ion distribution, the ion cooling is much slower than predicted by an adiabatic law linking the ion temperature to the ion density. The origin of this behavior is a strong distortion of the ion distribution function resulting in a large ion heat flow (not predicted by a simple water-bag model). Also noticeable is the increase of the electron heat flux in the unperturbed plasma compared to the zero ion temperature case.