Effects of energetic particles on zonal flow generation by toroidal Alfven eigenmode

TL;DR

This paper investigates how energetic particles drive zonal flows via toroidal Alfven eigenmodes, revealing a dominant nonlinear resonant EP contribution and a unique ZF generation mechanism related to EP-induced polarization.

Contribution

It introduces a new understanding of ZF generation by EP-driven TAE, highlighting the dominant nonlinear resonant EP effects over thermal plasma responses.

Findings

Nonlinear resonant EP contribution dominates ZF generation.

ZF can be linearly driven with a growth rate twice that of TAE.

Generated ZF exhibits meso-scale and micro-scale radial structures.

Abstract

Generation of zonal ow (ZF) by energetic particle (EP) driven toroidal Alfven eigenmode (TAE) is investigated using nonlinear gyrokinetic theory. It is found that, nonlinear resonant EP contri- bution dominates over the usual Reynolds and Maxwell stresses due to thermal plasma nonlinear response. ZF can be forced driven in the linear growth stage of TAE, with the growth rate being twice the TAE growth rate. The ZF generation mechanism is shown to be related to polarization induced by resonant EP nonlinearity. The generated ZF has both the usual meso-scale and micro- scale radial structures. Possible consequences of this forced driven ZF on the nonlinear dynamics of TAE are also discussed.