AMBIPOLAR DIFFUSION IN 2-TEMPERATURE MULTICOMPONENT PLASMAS

A recent formulation of multicomponent diffusion in multitemperature g as mixtures [J. D. Ramshaw, J. Non-equilib. Thermodyn. 18, 121 (1993)] is applied to ambipolar diffusion in two-temperature multicomponent p lasmas in zero magnetic field. Simplifications due to the small electr on mass are systematically exploited. A general expression is derived for the ambipolar electric field E. In the special case where the elec tron and heavy-particle temperatures are equal, this expression reduce s to a result previously obtained using a self-consistent effective bi nary diffusion (SCEBD) approximation [J. D. Ramshaw and C. H. Chang, P lasma Chem. Plasma Process. 11, 395 (1991)]. When thermal diffusion du e to electrons is neglected, the heavy particles are shown to diffuse precisely as they would in the same E field if the electrons were enti rely removed from the system. Finally, the SCEBD approximation for amb ipolar diffusion in multicomponent plasmas is generalized to the case of unequal electron and heavy-particle temperatures.