Geodesic Acoustic Mode

The Geodesic Acoustic Mode (GAM) is a plasma oscillation occurring in toroidal confinement devices with the following properties:

• Radially localized
• Axisymmetric (n=0)
• Poloidally symmetric potential (m=0) and asymmetric density (m=1) perturbations

The GAM frequency is, approximately:

$f_{GAM}\sim (1+1/2q^{2}){\frac {\sqrt {(T_{e}+T_{i})/M_{i}}}{2\pi R}}$