Drift of a plasma in a curved magnetic field

A plasma confined by an externally applied curved magnetic field will show an accelerated motion (`drift') to the region of weaker field. This motion is analysed in three different ways. In the first description the magnetohydrodynamic equation of motion is used, with the only assumption that no appreciable transverse accelerations are present. Secondly, the well-known microscopic picture (charge separation leading to E/B drift) is analysed for a β « 1 plasma with the guiding centre approximation. In the third model the change in the total energy of the system caused by a small outward displacement is considered. In all models the outward acceleration is found to be a R = 2 k ( T i + ZT e )/ Rm i where R is the radius of curvature of the field. The energy for the outward motion is partly supplied by the primary circuit and partly by an expansion of the plasma.