Novel computer simulation of electron swarm motion

A novel computer simulation technique for the study of properties of electron swarms in gases is presented. As an example, the method is applied to nitrogen at E/N values of 10^-16-10^-15 V cm². A strong directional anisotropy in the electron velocity distribution function is observed. The anisotropy is especially strong at electron energies for which the inelastic collision cross section is large relative to the total collision cross section. The first asymmetric term in the expansion of the distribution function in spherical harmonics can be as high as 70% of the value of the symmetric part of the distribution. A comparison with the computer simulation shows, however, that in spite of such strong anisotropy in nitrogen at these values of E/N, the solution of the Boltzmann equation based on the first two terms of the spherical harmonic expansion, gives correct values of electron drift velocity, average electron energy, and average vibrational excitation frequency.