On Nonlinear Scattering of Drift Wave by Toroidal Alfven Eigenmode in Tokamak Plasmas

TL;DR

This paper analytically investigates how nonlinear wave-wave interactions between drift waves and toroidal Alfvén eigenmodes affect plasma stability, revealing that such scatterings have negligible net impact on drift wave stability under typical conditions.

Contribution

It introduces an analytical study of nonlinear wave interactions between drift waves and TAE, highlighting their limited effect on drift wave stability in tokamak plasmas.

Findings

Scatterings to upper-sideband KAW lead to stimulated absorption of eDW.

Scatterings to lower-sideband KAW cause spontaneous emission.

Net effect on eDW stability is negligible under typical parameters.

Abstract

Using electron drift wave (eDW) as a paradigm model, we have investigated analytically direct wave-wave interactions between a test DW and ambient toroidal Alfv\'en eigenmodes (TAE) in toroidal plasmas, and their effects on the stability of the eDW. The nonlinear effects enter via scatterings to short-wavelength electron Landau damped kinetic Alfv\'en waves (KAWs). Specifically, it is found that scatterings to upper-sideband KAW lead to stimulated absorption of eDW. Scatterings to the lower-sideband KAW, on the contrary, lead to its spontaneous emission. As a consequence, for typical parameters and fluctuation intensity, nonlinear scatterings by TAE have negligible net effects on the eDW stability; in contrast to the ``reverse" process investigated in Ref. [Nuclear Fusion {\bf 62}, 094001 (2022)], where it is shown that nonlinear scattering by ambient eDW may lead to significant damping of TAE.