# Electromagnetic turbulence suppression by energetic particle driven modes

## TL;DR

This paper investigates how energetic particle driven modes suppress electromagnetic turbulence in magnetic confinement plasmas, revealing nonlinear interactions that enhance plasma stability and reduce transport.

## Contribution

It provides a detailed nonlinear analysis showing that marginally stable energetic particle modes deplete turbulence energy and promote zonal flow formation, explaining turbulence suppression.

## Key findings

- Nonlinear excitation of energetic particle modes reduces turbulence.
- Energetic particles facilitate energy transfer to zonal modes.
- Simulations match experimental observations of reduced transport.

## Abstract

In recent years, a strong reduction of plasma turbulence in the presence of energetic particles has been reported in a number of magnetic confinement experiments and corresponding gyrokinetic simulations. While highly relevant to performance predictions for burning plasmas, an explanation for this primarily nonlinear effect has remained elusive so far. A thorough analysis finds that linearly marginally stable energetic particle driven modes are excited nonlinearly, depleting the energy content of the turbulence and acting as an additional catalyst for energy transfer to zonal modes (the dominant turbulence saturation channel). Respective signatures are found in a number of simulations for different JET and ASDEX Upgrade discharges with reduced transport levels attributed to energetic ion effects.