Collisional damping of the geodesic acoustic mode with poloidal rotation

Abstract

The collisional damping of the geodesic acoustic mode is investigated by using the gyrokinetic equation with a poloidal rotation flow and a number-conserving Krook collision operator. A dispersion relation of the geodesic acoustic mode with poloidal rotation and collision terms is derived and solved both analytically and numerically. It is shown that poloidal rotation has a significant influence on the collisional damping rate of the geodesic acoustic mode within a certain collision rate and safety factor domain. The variation of the damping rate induced by poloidal rotation depends on the safety factor and collision rate. In addition, the effect of poloidal rotation on the geodesic acoustic mode would be weakened by the safety factor, especially when the safety factor is relatively large. The ratio of the collisional damping rate to the collisionless damping rate of the geodesic acoustic mode in the large safety factor domain is performed, and the critical collision rate is estimated. Besides, the physical mechanism of the results is briefly discussed.