The ion cyclotron parametric instabilities and the anomalous heating of ions in the tokamak edge plasma in the fast wave heating regime

Abstract

The theory of the ion cyclotron (IC) electrostatic parametric instabilities of plasma, which are driven by the elliptically polarized fast wave (FW) of the finite wavelength, is developed. This theory provides the analytical treatment of the parametric instabilities with wavelengths comparable with the displacements of ions relative to electrons in the FW. The numerical solution of the dispersion equation for a three wave system that contains the IC mode and two beat waves with frequencies equal to the difference of the IC mode frequency and harmonics of the FW is performed. It reveals the parametric IC instability for this wave system with the maximum growth rate for the IC waves with wavelengths comparable with the thermal ion Larmor radius. The anomalous heating rates of ions resulting from the interactions of ions with parametric IC turbulence are determined employing the developed quasilinear theory for the IC quasimode decay instability. The derived results reveal that the experimentally observed anisotropic heating of cold scrape-off layer (SOL) ions may be the result of the interaction of the SOL ions with IC parametric turbulence. However, the IC parametric turbulence is unlikely to be responsible for the experimentally observed bursts of poorly confined suprathermal ions in the SOL of tokamak plasmas.