Charged-neutral collision models in the presence of drifts

Abstract

A charged-neutral collision model is presented for application to the kinetic theory of weakly ionized plasmas with immobile neutrals. The model is a modification of the well-known Bhatnagar-Gross-Krook model, which has been the main model used in space plasmas so far. In comparison, the new model produces self-consistently correct zero order drifts, and properly behaved zero order evolutions, while otherwise leaving identically unchanged all the kinetic dispersion equations of space plasma instabilities derived by the old model. Also, the present model allows to use directly the zero order κ-distributions recently introduced by Summers and Thorne [Phys. Fluids B 3, 1835 (1991)] for space plasmas, as input parameters, to which the actual distribution relaxes in time, as well as their generalized plasma dispersion function Zκ*(z) for the solution of dispersion equations. The new model is compared throughout to a previous model by Mikhailovskii and Pogutse [Sov. Phys. Tech. Phys. 11, 153 (1966)], which also produces the correct zero order drifts, but predicts autonomously the zero order distribution.