Nonlinear saturation of toroidal Alfven eigenmodes via nonlinear mode couplings

TL;DR

This paper presents a gyrokinetic theory explaining how nonlinear mode couplings can saturate toroidal Alfven eigenmodes in fusion plasmas, highlighting multiple comparable processes such as parametric decay and ion scattering.

Contribution

It introduces a comprehensive gyrokinetic framework for TAE saturation, incorporating parametric decay and ion scattering mechanisms, which were not simultaneously detailed before.

Findings

Multiple nonlinear processes can equally contribute to TAE saturation.

Parametric decay into LKTAE and GAM is significant.

Ion-induced scattering enhances TAE coupling to the shear Alfven wave continuum.

Abstract

Gyrokinetic theory of nonlinear mode coupling as a mechanism for toroidal Alfven eigenmode (TAE) saturation in the fusion plasma related parameter regime is presented, including 1) para- metric decay of TAE into lower kinetic TAE (LKTAE) and geodesic acoustic mode (GAM), and 2) enhanced TAE coupling to shear Alfven wave (SAW) continuum via ion induced scattering. Our theory shows that, for TAE saturation in the parameter range of practical interest, several processes with comparable scattering cross sections can be equally important.