Linear collisionless dynamics of the GAM with kinetic electrons: Comparison simulations/theory

Abstract

Barely trapped and passing electrons have been recently predicted to strongly enhance the damping rate of Geodesic Acoustic Modes (GAMs) in tokamak plasmas, while keeping their real frequency almost unchanged as compared to the case with adiabatic electrons. In this paper, dedicated gyrokinetic simulations are successfully compared with these analytical predictions. Specifically, the scaling of the GAM damping rate with respect to the ion to electron mass ratio, to the electron to ion temperature ratio, to the safety factor, and to the aspect ratio is recovered in most regions of the relevant parameter space.