Collisional magnetic pumping revisited

In this paper, the authors explore the consequences of applying to the exciter coil a RF current which is either full wave rectified, B=B/sub o/(1+δ(1+cosωt)), or which is a sinusoidal excitation with a DC bias magnetic field applied only in the axial region subtended by the exciter coil, B=B/sub o/(1+δ(1+cosωt)). In both these cases, the conservation of the magnetic moment will lead to an increase in the perpendicular components of velocity above the equipartition values outside the exciter coil, but not to a decrease. Thus any stochastic process, including collisions in the heating region, is much more likely to achieve a net energy transfer to the parallel velocity component. This should lead to a heating rate linearly proportional to the modulation δ , rather than to its square. If ions are scattered by fluctuating electric fields originating from strong plasma turbulence, this can lead to an effective collision frequency higher than the binary collisional value, and to greatly enhanced ion heating rates