Electron Velocity Distributions in a Partially Ionized Gas

Abstract

The Boltzmann method is applied to the problem of calculating the electron velocity distribution in a partially ionized gas. Inelastic collisions with neutral molecules as well as random two-body Coulomb interactions are included. The latter are treated by use of the Fokker-Planck equation. Application is made to a hydrogen plasma subjected to an externally applied electric field. Static solutions are obtained, by numerical means, as a function of the ionization degree, and the classical gas discharge parameter, $\frac{E}{p}$. It is shown that the evolution of the electron velocity distribution function from that characteristic of a poorly ionized gas to the Maxwellian distribution occurs over a very large range in ionization degree. Several applications are also made to energy relaxation phenomena, and the electrical conductivity is evaluated.