On the simulation of gas ionization by fast electrons

The gas-dynamic parameters of an ionized medium formed during impact ionization of a rarefied gas by fast electrons are considered. The concentration, drift velocity, and specific energy of low-energy secondary electrons are constructed by an approximate solution of the kinetic equation. Approximations of the spatial homogeneity of the kinetic equation and the isotropy of the initial distribution of secondary electrons during impact ionization are used. Additional approximations are related to the structure of the distribution function of secondary electrons and averaging of the cross sections.