Title: Excitation of GAM by RSAE in nonuniform plasmas.
Abstract:
Effects of system nonuniformities and kinetic dispersiveness on the spontaneous excitation of Geodesic Acoustic Mode (GAM) by Reversed Shear Alfv\'{e}n Eigenmode (RSAE) are investigated. The physical model is derived based on gyrokinetic theory. The nonlinear excitation of GAM by RSAE is a convective instability by taking account the finite group velocities due to kinetic dispersiveness in uniform plasmas. The nonuniformity of RSAE continuum renders the convective parametric instability into a quasi-exponentially growing absolute instability in nonuniform plasmas.