On nonlinear scattering of drift wave by toroidal Alfvén eigenmode in tokamak plasmas

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 Alfvén eigenmodes (TAEs) 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 Alfvén 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 TAEs have negligible net effects on the eDW stability; in contrast to the ‘reverse’ process investigated in Chen et al (2022 Nucl. Fusion 62 094001), where it is shown that nonlinear scattering by ambient eDWs may lead to significant damping of TAE.