Momentum Balance Current Filaments in Magnetic Fields

摘要

Based on the momentum equation, the impulse transport from a current-carrying plasma filament to the surrounding nonconductive gas is found to be a function of the current, the magnetic field, the filament radius and the radius of curvature of the current streamer. This impulse transport normal to the discharge axis per unit time and length arises from convective and/or diffusive interactions between the filament and its nonconductive environment. The momentum exchange per unit filament represents a transverse force varying between zero and IBo. It may become zero if the Lorentz force is balanced by the inertia of the current-carrying particles within the filament; conversely, it reaches a maximum when the Lorentz force is opposed by gas dynamic reaction forces between the filament and the surrounding plasma. This latter case usually occurs when the motion of electrons and ions within the filament is collision-dominated and no net axial plasma flow is present. Since the transverse exchange mode constitutes a known balance of forces, one is able to determine the curvature behavior and the shape of a filament in a given magnetic field configuration. Characteristic stable filament structures are presented. (Author)