Nonlinear excitation of a geodesic acoustic mode by reversed shear Alfvén eignemodes

Abstract

Abstract The parametric decay process of a reversed shear Alfv\'{e}n eigenmeode (RSAE) into a geodesic acoustic mode (GAM) and a kinetic reversed shear Alfv\'{e}n eigenmode (KRSAE) is investigated using nonlinear gyrokinetic theory. The excitation conditions mainly require the pump RSAE amplitude to exceed a certain threshold, which could be readily satisfied in burning plasmas operated in steady-state advanced scenario. This decay process can contribute to thermal plasma heating and confinement improvement.