Interplay between fast ions and turbulence in magnetic fusion plasmas
Plasma Physics and Controlled Fusion
Evidence for the impact of energetic particles (EPs) on turbulence is given in this paper. Firstly, the excitation of electrostatic instabilities in linear gyrokinetic simulations performed with the global gysela code by introducing distribution functions typical of fast ions in tokamak plasmas is presented. The obtained mode is unambiguously characterized as an EGAM, i.e. a Geodesic Acoustic Mode (GAM) excited by EPs. The influence of EGAMs on turbulence and associated transport is then
... d by implementing a source adapted to the inclusion of fast particle populations in non-linear simulations. This source successfully excites EGAMs in the presence of turbulence, and leads to a drastic reduction of the turbulent transport. However, this reduction is only transient, and is followed by an increase of the turbulent activity, characterized by a complex interaction between the EGAMs and turbulence. In the subsequent steady-state regime, turbulent transport appears to be modulated at the EGAM frequency.