QUASI-HYDRODYNAMIC DESCRIPTION OF ION-ACOUSTIC-WAVES IN A COLLISIONAL PLASMA

A quasihydrodynamic description of ion acoustic waves (IAW) has been developed in the entire range of particle collisionality. It is shown that a frequency dependent 21-moment Grad closure to ion fluid equations and phenomenological delocalized electron heat transport formulation can be used for an accurate analytical description of ion acoustic wave dispersion and damping. This description is in good agreement with the results of Fokker-Planck simulations. The authors' new model has been derived with the practical motivation of improving IAW description in large scale numerical modeling of ion wave instabilities. This theory has been also applied to the linear analysis of heat flux driven plasma instabilities. In particular, a new IAW instability in the regime of collisional electrons, which is induced by the density dependence of the electron thermal transport coefficient, has been found.