Modification of Symmetry of Poloidal Eigenmode of Geodesic Acoustic Modes

Abstract

The poloidal eigenmode of the geodesic acoustic mode (GAM) is analyzed in the case of high aspect ratio circular plasmas, and an analytic representation for poloidal eigenfunction is derived. The m = ±1 and m = ±2 (m is the poloidal number) components of eigenfunction show up-down antisymmetry and up-down symmetry, respectively, in a torus. The mixing of the up-down symmetric and antisymmetric components becomes significant, when the ion gyroradius is large or when electron temperature is higher than ion temperature.