Non-thermal effect of electron cyclotron resonance heating on the Alfvén eigenmodes

Abstract

The combined effect of the plasma pressure gradient and the radial electric drift induced by horizontal polarization of the plasma during electron cyclotron resonance heating (ECRH) on the Alfvén eigenmodes is investigated. Two cases are considered: the reversed-shear Alfvén eigenmode (RSAE) and the toroidal Alfvén eigenmode (TAE). RSAE is completely eliminated at a fairly low ECRH power provided the flux surfaces at the mode location are properly polarized, i.e., negative (positive) excessive charge at the low (high) field side. In contrast, no significant effect on the TAE is found for realistic ECRH powers deposited close to the toroidal gap location. The possible relation of these results with recent experiments in tokamaks is discussed.