Electron Distribution Function for a Nonequipartition Plasma in a Strong Electric Field

Solutions to the kinetic equation of a steady, homogeneous plasma of arbitrary degree of ionization subjected to strong electric fields are developed. Nonelastic as well as elastic encounters are included in the analysis. Expressions for the current density, electrical conductivity, and electron temperature of the plasma are also presented. Numerical results are illustrated for the case when the nonelastic effects are neglected. Calculations are presented showing the transition of the isotropic part $f^0$ of the distribution function from a gas‐temperature Maxwellian at near equilibrium conditions to an electron‐temperature Maxwellian under nonequipartition conditions. It was found that whenever the electron‐electron to electron‐neutral collision‐frequency ratio was much greater than the electron‐to‐heavy‐particle mass ratio, $f^0$ is Maxwellian. When $f^0$ is Maxwellian, the Chapman‐Enskog and Spitzer‐Härm conductivity expressions developed for the case of weak electric fields are shown to be applicable for strong electric fields providing that in these expressions the electron temperature replaces the gas temperature. An approximate form for $f^0$ suggested by Ginzburg is compared with the exact expression. The accuracy of the use of a Maxwellian rather than the nonequilibrium distribution function in the calculation of the electrical conductivity is assessed.