The generalized hydrodynamic equations for arbitrary collision frequency in a weakly ionized plasma

Abstract

Electron transport processes in a weakly ionized plasma with elastic electron-neutral collisions are studied by using the hybrid fluid/kinetic approach. The standard hierarchy of fluid moment equations is closed with expressions for higher hydrodynamic moments (heat flux and viscosity) in terms of the lower moments (temperature, density, and fluid velocity). The heat fluxes and viscosity moments are determined in the linear approximation from the kinetic equation in the Chapman–Enskog form. The obtained system of moment equations describe the transport processes in weakly ionized plasmas in the most general ordering, when the electron mean free path vTe/νe is arbitrary with respect to the characteristic length scale k−1 of the system’s inhomogeneity, and collision frequency νe is arbitrary with respect to the characteristic frequency ω. General expressions for the nonlocal (time and spatial dependent) transport coefficients are obtained. In the nonlocal limit, kvTe≫νe, the derived transport coefficients describe the wave–particle (Landau) interaction effects. Implications of nonlocal effects on plasma heating mechanisms are discussed.