Nonlinear excitation of geodesic acoustic mode by toroidal Alfvén eigenmodes and impact on plasma performance

Abstract

Spontaneous nonlinear excitation of geodesic acoustic mode (GAM) by toroidal Alfvén eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found that, the nonlinear decay process depends on thermal ion βvalue. Here, βis the plasma thermal to magnetic pressure ratio. In the low-βlimit, TAE decays into a GAM and a lower TAE sideband in the toroidicity induced shear Alfvén wave continuous spectrum gap; while in the high-βlimit, TAE decays into a GAM and a propagating kinetic TAE in the continuum. Both cases are investigated for the spontaneous decay conditions. The nonlinear saturation levels of both GAM and daughter wave are derived. The corresponding power balance and wave particle power transfer to thermal plasma are computed. Implications on thermal plasma heating are also discussed.

arXiv commentsubmitted to Nuclear Fusion

References in corpus (4)

• Nonlinear dynamics of phase space zonal structures and energetic particle physics in fusion plasmas
• Effects of energetic particles on zonal flow generation by toroidal Alfven eigenmode
• Nonlinear excitation of fine-radial-scale zonal structures by toroidal Alfven eigenmode
• Nonlinear dynamics of Shear Alfvén fluctuations in Divertor Tokamak Test facility plasmas

Cited by in corpus (4)

• Nonlinear reversed shear Alfven eigenmode saturation due to spontaneous zonal current generation
• H-mode transition in the TJ-II stellarator plasmas
• High frequency mode generation by toroidal Alfven eigenmodes
• Evidence of "Two Plasmon" decay of energetic particle induced geodesic acoustic mode