Kinetic treatment of parallel gradient nonuniformity for the ICRF heating—A fourier integral approach

Abstract

We study the generally nonlocal Vlasov‐Maxwell wave propagation and absorption problem for an arbitrarily nonuniform plasma. The Fourier transform of the nonlocal dielectric response kernel, K(r,k), is constructed by integration along particle orbits in the nonuniform field. Although a finite Larmor radius expansion of the transverse particle motion still applies, the phase integrals which comprise the usual plasma dispersion function are altered, containing an additional parameter characterizing the parallel field gradient. The use of realistic phase decorrelation estimates over a single bounce orbit leads to a reduction of the phase integrals to a tractible form. We numerically solve a 1‐D sheared field version of the resultant integral equation describing the mode conversion physics. Significant changes are found for small k∥ values. In addition, local absorption in the resonance zone appears to be stratified in conjunction with the rf‐particle phase correlation which occurs for particles passing through the localized resonance.