EHD and EMHD Transport Processes in Dusty and Dirty Plasmas

Abstract

Dusty or dirty plasmas may be considered a plasma environment containing charged dust grains or aerosols, fully or partially ionized, collisionless or collisional. In the laboratory, examples are nuclear fusion devices with impurity ions and atoms, electric discharge, and plasma synthesis for recent industrial applications, while examples in space are thunderstorms and tornadoes, planetary rings, cometary and interstellar dusts. In such environments, electric rather than magnetic processes are taking place predominantly involving electric charging and discharge, ionization and recombination, particle disruption and coalescence, and space charge transport. For these phenomena, conventional hydrodynamics (HD) or magnetohydrodynamics (MHD) breaks down, and even conventional plasma physics is not relevant, since they usually ignore the effects of space charges, electric, and inter-gravitational fields. Furthermore, most of their environments are considered neither conducting fluids, fully ionized gases nor collisionless plasmas. They may be partially ionized, collisional gases, semiconducting or dielectric fluids where electrohydrodynamic (EHD) or more generally electromagnetohydrodynamic (EMHD) transport processes are taking place significantly rather than HD or MHD processes. This paper concerns these EHD and EMHD transport processes involving new electric and space charge transport in addition to conventional fluid vortex and magnetic field transport. For such an EHD or EMHD regime, a new equation of electric field transport is obtained, including space charge, ponderomotive, and gravitational forces, and is supplemented by the equations of vorticity, magnetic field, and energy transport extended also for this new regime. The “electric Reynolds number” newly introduced, analogous to the Reynolds and magnetic Reynolds numbers plays an important role in the EHD and EMHD regimes as a criterion of relative importance of convection, diffusion, dissipation, propagation, and radiation.