MODELING HEATING AND CURRENT DRIVE IN THE ION-CYCLOTRON FREQUENCY-RANGE

Numerical simulation of heating and current drive in the ion cyclotron frequency range has progressed to the point that both the propagation and absorption of IC waves on the one hand, and the evolution of ion and electron distribution functions due to interaction with the h.f. fields on the other hand, can now be described in realistic geometry and to some extent consistently with each other. We review recent work in this field, with particular emphasis on the derivation and numerical solution of adequate equations to describe wave propagation in hot plasmas in toroidal geometry. Codes solving the quasilineax kinetic equations and their interface to wave propagation codes axe also briefly mentioned. The complete problem is so complex, however, that in most cases simplified models must be used for extensive numerical studies of IC heating and current drive scenarios. Plane stratified models are appropriate to investigate antenna loading and global power balance; ray tracing gives excellent results in large hot plasmas and are easily interfaced to quasilinear kinetic codes. Full-wave codes in toroidal geometry are often simplified by neglecting either finite Larmor radius effects or the poloidal component of the static magnetic field, or both. We summarise as far as possible the purpose and limits of each approach, particularly from the point of view of using the results in combination with solvers of the quasilinear kinetic equations, or with simulations of transport in tokamaks. We also try to clarify some discrepancies between different codes arising from inconsistent approximations.