Magnetohydrodynamic description of collisionless plasma expansion in the upper atmosphere

Abstract

Collisionless plasma cloud expansion into an extremely rarefied ionized medium is considered in the presence of a magnetic field when the medium is involved in the motion and the cloud is retarded due to the electromagnetic interactions. The Collisionless flow is computed on the basis of a hybrid model, in which the ionic motions are considered by means of kinetic equations and the electrons are governed by a hydrodynamic equation. The numerical results of the same explosion problem according to the Collisionless, hybrid, and magnetohydrodynamic models are compared and good agreement is shown. This justifies the use of hydrodynamics to describe the flows with rare collisions when formulating the general ideas on explosions in the upper ionosphere.