Transport equations for aeronomy

In this paper we present results for a general system of transport equations appropriate to a multi-constituent gas mixture. This system includes a continuity, momentum, internal energy, pressure tensor and heat flow equation for each species. The results can be applied to both collision dominated and collisionless plasmas with there being explicit limits derived for the validity of the various expressions. In the limit of very frequent collisions the pressure tensor and heat flow equations give the usual Navier-Stokes results for the viscous stress tensor and heat flow vector. Furthermore, the momentum equation includes thermal diffusion and thermoelectric transport coefficients equivalent to the second approximation of Chapman and Cowling. The basic system of equations has been applied to different regions of the ionosphere and neutral atmosphere. It is found that: (1) The viscous stress tensor and heat flow expressions used in previous studies of the neutral thermosphere may not be appropriate; (2) The transport coefficients normally used for mid-latitude F2-region and topside studies seem to be adequate; (3) The high speed flow of plasma in the polar topside ionosphere is likely to be strongly affected by stresses and heat flow; and (4) E- and F-region ionization at high latitudes is substantially affected by stresses and heat flow.