The Influence of Induced Currents on Magnetic Nozzle Acceleration and Plasma Detachment


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The Influence of Induced Currents on Magnetic Nozzle Acceleration and Plasma Detachment


Abstract

The influence of induced currents on the acceleration and detachment of a uniform plasma expanding through a magnetic nozzle is investigated. A collisionless two-fluid model is used to solve for the flow of a cold-ion, hot-electron plasma through a diverging magnetic field. An iterative procedure is then employed to converge upon a magnetic field solution consistent with the plasma dynamics. The ratio of the kinetic energy density to the magnetic field energy density at the nozzle throat, β0, is found to control the relative importance of induced currents within the flow while the acceleration of the plasma is largely independent of β0. The efficiency at which the plasma detaches from the magnetic nozzle, on the other hand, increases with β0 due to the influence of induced magnetic fields on the plume divergence. Finally, it is concluded that the predominant physical mechanism behind plasma detachment is the inertial separation of the flow from the magnetic field as the electron Larmor radius increases beyond the scale length of magnetic field variation. The local value of β at the detachment location reflects the relative importance of induced currents on plasma detachment