Nonlinear ion motion in a slow ion cyclotron mode

Abstract

The nonlinear cyclotron resonance of a single ion in a coherent slow ion cyclotron wave is treated analytically, at first, for an arbitrary angle of propagation in a homogeneous magnetic field. It is found that for tokamak plasma parameters the nonlinear phase space orbits are characterized by parallel propagation, and, for this case, simple approximate expressions are obtained for the gyroradius and parallel velocity of the resonant particle. The nonlinear period is obtained, and an invariant is found which extends the theory to a system with slowly changing parameters. It also is found that heating occurs in the perpendicular direction, and cooling in the parallel direction.