High Frequency Geodesic Acoustic Modes in Electron Scale Turbulence

Abstract

In this work the finite $\beta$-effects of an electron branch of the geodesic acoustic mode (el-GAM) driven by electron temperature gradient (ETG) modes is presented. The work is based on a fluid description of the ETG mode retaining non-adiabatic ions and the dispersion relation for el-GAMs driven non-linearly by ETG modes is derived. The ETG growth rate from the fluid model is compared to the results found from gyrokinetic simulations with good agreement. A new saturation mechanism for ETG turbulence through the interaction with el-GAMs is found, resulting in a significantly enhanced ETG turbulence saturation level compared to the mixing length estimate. It is shown that the el-GAM may be stabilized by an increase in finite $\beta$ as well as by increasing non-adiabaticity. The decreased GAM growth rates is due to the inclusion of the Maxwell stress.

15 pages, 4 figures. Presented at the IAEA conference 2012

References in corpus (5)

• Nonlinear entropy transfer via zonal flows in gyrokinetic plasma turbulence
• Zonal flow generation in ion temperature gradient mode turbulence
• Zonal flow generation in collisionless trapped electron mode turbulence
• Comparison of multi-scale analysis models applied to zonal flow generation in ion-temperature-gradient mode turbulence
• High Frequency Geodesic Acoustic Modes in Electron Temperature Gradient Mode Turbulence

Cited by in corpus (1)

• Geodesic acoustic modes in a fluid model of tokamak plasma : the effects of finite beta and collisionality