# Geodesic Acoustic Mode

From FusionWiki

The Geodesic Acoustic Mode (GAM) is a plasma oscillation occurring in toroidal confinement devices with the following properties:
^{[1]}
^{[2]}
^{[3]}

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

The GAM frequency is, approximately:^{[2]}

- $ f_{GAM} \sim (1+1/2q^2)\frac{\sqrt{(T_e+T_i)/M_i}}{2\pi R} $

## References

- ↑ N. Winsor, J.L. Johnson and J.M. Dawson,
*Geodesic Acoustic Waves in Hydromagnetic Systems*, Phys. Fluids**11**(1968) 2448 - ↑
^{2.0}^{2.1}K.J. Zhao et al.,*Toroidal Symmetry of the Geodesic Acoustic Mode Zonal Flow in a Tokamak Plasma*, Phys. Rev. Lett.**96**(2006) 255004 - ↑ Z. Gao,
*Collisional damping of the geodesic acoustic mode*, Phys. Plasmas**20**(2013) 032501