On sub-Alfven MHD flows with acceleration in coaxial channels

Magnetohydrodynamic (MHD) flows in coaxial channels of plasma accelerators with a longitudinal magnetic field are considered. Sub-Alfven MHD flows with acceleration transonic to the slow magnetosonic speed are studied. Sub-Alfven MHD flows are related to the case when the plasma flow velocity doesn't exceed the Alfven speed corresponding to the longitudinal field along the channel. A narrow coaxial nozzle channel with a constant lower bound is considered. The non-stationary and stationary mathematical MHD models are considered in the quasi-one-dimensional approximation. The corresponding MHD problems are solved numerically. Features of the relaxation process and characteristics of the transonic sub-Alfven flow type with acceleration in the channel are studied. The influence of the longitudinal magnetic field on the steady-state plasma flows are researched. The mechanism of energy transformations is described. (paper)