Gyrokinetic investigation of Alfv\'en instabilities in the presence of turbulence

TL;DR

This paper investigates how beta-induced Alfvén Eigenmodes interact with ion-temperature-gradient turbulence in a tokamak, revealing their role in modifying heat fluxes and plasma profiles through gyrokinetic simulations and theory.

Contribution

It extends previous studies by analyzing the nonlinear interaction of BAEs with turbulence in a realistic tokamak setting, highlighting the electron heat flux contribution.

Findings

BAEs modify heat fluxes at large scales

BAEs carry strong electron heat flux

Interaction influences plasma temperature profiles

Abstract

The nonlinear dynamics of beta-induced Alfv\'en Eigenmodes (BAE) driven by energetic particles (EP) in the presence of ion-temperature-gradient (ITG) turbulence is investigated, by means of selfconsistent global gyrokinetic simulations and analytical theory. A tokamak magnetic equilibrium with large aspect ratio and reversed shear is considered. A previous study of this configuration has shown that the electron species plays an important role in determining the nonlinear saturation level of a BAE in the absence of turbulence [A. Biancalani, et al., J. Plasma Phys. (2020)]. Here, we extend the study to a turbulent plasma. The EPs are found modify the heat fluxes by introducing energy at the large spatial scales, mainly at the toroidal mode number of the dominant BAE and its harmonics. In this regime, BAEs are found to carry a strong electron heat flux. The feed-back of the global relaxation of the temperature profiles induced by the BAE, and on the turbulence dynamics, is also discussed.