Kinetic effects in Alfven wave heating. Part II: Propagation and absorption with a single minority species

The effects of a heavy minority on Alfven wave heating are examined in a linearized circular cylindrical tokamak model. It is shown that a suitable minority concentration and radially varying charge profile produces a two-ion hybrid resonance in the plasma interior and an Alfven wave resonance near the edge. The latter situation, which gives rise to cold plasma surface Alfven eigenmodes (SAE's), was described in Part I [Phys. Fluids B 1, 2353 (1989)] for a pure plasma. Here, numerical results, exhibiting substantial absorption in the hybrid layer as a result of the dissipation of these modes, are presented. It is shown that the poloidal mode number strongly affects the amount of the energy absorbed in the hybrid layer. Generally, electron heating due to electron Landau and collisional damping of SAE's and two-ion hybrid fields [ω>(ωc2)max, with ωc2 being the fundamental minority gyrofrequency] dominates minority heating excepting for cases when kparallel, the parallel wavenumber, is large enough that no SAE occurs near the plasma edge. For the larger kparallel system, there occurs a stronger coupling between the two-ion hybrid and fundamental minority gyroresonance layers, resulting in comparable electron and minority heating. The majority heating is zero everywhere because ω<(ωc1)min, where ωc1 is the fundamental majority gyrofrequency