Parametric Excitation of Geodesic Acoustic Modes by Electron Drift Waves and Ion Temperature Gradient Modes in Tokamak Plasmas

摘要

Geodesic Acoustic Modes (GAMs) have been predicted and subsequently observed in many toroidal plasma devices. Bicoherence studies on various devices have suggested threewave mode coupling processes between GAMs and high frequency turbulence. Thus the parametric coupling of GAMS to drift waves and/or ion temperature gradient(ITG) modes is a potential candidate for excitation of these modes. In this paper we discuss the resonant threewave coupling mechanism for the excitation of GAMs by ITG and finite beta drift waves in homogeneous and inhomogeneous plasmas and compare theoretical predictions with observed characteristics of the GAMs.