Plasma transport under the conditions of current passage

A transport equation has been derived for a plasma treated as a continuous medium. In contrast to the well-known magnetohydrodynamic approach, in deriving the equation, the spatial charge density was taken into account which has made it possible to determine the self electric field of the plasma and the consistent motion of charged particles of different charge sign. Analysis of the equation terms that describe the contributions of various types of energy to the plasma transport has been performed. In the limit of dominant thermal energy, the criteria for plasma quasineutrality and ideality transforms into the well-known criterion defined by the squared ratio of the Debye radius to the characteristic size, and plasma transport is reduced to ambipolar diffusion. Based on the equation obtained, models of moderate-pressure and atmospheric-pressure glow discharges can be considered to interpret experiments with fields too low to provide ionization, so that a bulk plasma is sustained by charge carriers coming from near-electrode regions, and the cross-section of the current filament is determined by the balance of forces that represent the action of the thermal energy and of the energy of electrical interaction between the plasma particles.