Interaction of a plasma flow with a magnetic dipole field

Abstract

The interaction of a streaming plasma with a magnetic dipole field is studied in the framework of a linearized, two-fluid continuum description. For the case of low-density flows, in which the pressure gradients are small in comparison to magnetic and electric forces, it is possible to extend the solution beyond the first-order one, which gives the distribution of induced current in the azimuthal direction, and calculate space-charge density and plasma potential distributions, along with the Hall current components in a restricted spatial region. The quantities of second-order scale directly with the appropriate Cowling number, whereas the azimuthal current density increases with the square root of this ratio. It is also shown that the Hall current densities and potential variation increase rapidly with increasing plasma density, while the normalized space charge density scales with the square of the plasma velocity. Moreover, the theory predicts a significant decrease in plasma potential in the vicinity of the dipole; a result which tends to agree with recent experimental indications.