The Electrical Conductivity of a Partially Ionized Gas

The electrical conductivity of a low density and partially ionized gas where both electron-neutral particle and Coulomb type collisions play important roles is discussed. The effects of inelastic collisions and a steady magnetic field are not considered. We assume that the ionized gas is perturbed by a weak electric field, and obtain the velocity distribution function for the electrons by solving the Boltzmann equation; the collision between neutral and charged particles is accounted for by the hard sphere model for the particles, while the collision between the charged particles is taken care of by the Fokker-Planck terms. Explicit expressions for ac and dc conductivity are given for various cases. To the extent that the assumptions made for the collision models are valid, the expressions for conductivity given here are quite general and can be used for any degree of ionization.