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

TL;DR

This study uses gyrokinetic simulations to explore how Alfvén modes interact with ion temperature gradient turbulence in a magnetically confined plasma, revealing mutual enhancement of transport phenomena.

Contribution

It provides the first self-consistent simulation of Alfvén modes interacting with ITG turbulence in a reversed shear magnetic equilibrium.

Findings

Alfvén mode saturates with turbulence, dominating ion heat flux.

Unstable Alfvén mode enhances ITG-induced transport.

Ion heat flux is primarily driven by the saturated Alfvén mode.

Abstract

The global and electromagnetic gyrokinetic particle-in-cell code ORB5 is employed to investigate the self-consistent interactions between Alfv\'en modes (AM) and ion temperature gradient (ITG) turbulence in a magnetically confined plasma. Here, an axisymmetric magnetic equilibrium with reversed shear and large aspect ratio is considered. An AM with toroidal mode number n=5 is driven unstable by introducing a population of suprathermal ions. Once the AM saturates in the presence of the fully developed turbulence, the ion heat flux is dominated by the AM and its main harmonics. ITG-induced transport is found to also be enhanced in the presence of the unstable AM.