Gyrokinetic theory of fast wave transmission with arbitrary parallel wave number in a nonuniformly magnetized plasma

The gyrokinetic theory of ion cyclotron resonance is extended to include propagation at arbitrary angles to a straight equilibrium magnetic field with a linear perpendicular gradient in strength. The case of the compressional Alfven wave propagating in a D(3He) plasma is analyzed in detail. A self-consistent local dispersion relation is obtained using a single mode description; this approach enables three-dimensional effects to be included and permits efficient calculation of the transmission coefficient. The dependence of this quantity on the species density ratio, minority temperature, plasma density, magnetic field, and equilibrium scale length is obtained. A self-consistent treatment of the variation of the field polarization across the resonant region is included. Families of transmission curves are given as a function of the normalized parallel wave number for parameters relevant to JET [see, for example, J. Jacquinot et al., Plasma Phys. 30, 1467 (1988)]. Perpendicular absorption by the minority ions is also discussed, and shown to depend on a single parameter, the ratio of the ion thermal velocity to the Alfven speed