Nonlinear gyrofluid computation of edge localised ideal ballooning modes

TL;DR

This paper presents 3D electromagnetic gyrofluid simulations of edge localized modes in tokamaks, analyzing energy transfer, turbulence, and parameter effects during ELM blowout events.

Contribution

It introduces a nonlinear gyrofluid model capturing the evolution of ELMs with detailed energetic and turbulence diagnostics, including equilibrium evolution and spectrum convergence.

Findings

Approximately two thirds of edge energy is released during blowout

Transition to nonlinearity resembles generic tokamak edge turbulence

Convergence requires spectrum reaching ion gyroradius

Abstract

Three dimensional electromagnetic gyrofluid simulations of the ideal ballooning mode blowout scenario for tokamak edge localized modes (ELMs) are presented. Special emphasis is placed on energetic diagnosis, examining changes in the growth rate in the linear, overshoot, and decay phases. The saturation process is energy transfer to self generated edge turbulence which exhibits an ion temperature gradient (ITG) mode structure. Convergence in the decay phase is found only if the spectrum reaches the ion gyroradius. The equilibrium is a self consistent background whose evolution is taken into account. Approximately two thirds of the total energy in the edge layer is liberated in the blowout. Parameter dependence with respect to plasma pressure and the ion gyroradius is studied. Despite the violent nature of the short-lived process, the transition to nonlinearity is very similar to that found in generic tokamak edge turbulence.