Geodesic Acoustic Mode Excitation by Drift Waves in Tokamak Plasmas with Toroidal Rotation

Nonlinear excitation of geodesic acoustic mode by drift waves is investigated in toroidally rotating tokamak plasmas using the ideal magnetohydrodynamic equations. It is found that both the radial wave number and the nonlinear growth rate of the driven geodesic acoustic mode increase with the speed of the toroidal rotation, where the decisive factor is the frequency shift of the geodesic acoustic mode induced by the toroidal rotation. The additional nonlinear terms induced by the toroidal rotation velocity make little effect, even though they promote the nonlinear excitation at all times.