Evolution of self-organized structure, the internal transport barrier in the ion-temperature-gradient driven gyrokinetic turbulence

TL;DR

This paper investigates the formation and evolution of the internal transport barrier in fusion plasmas using advanced gyrokinetic simulations, revealing the mechanisms behind its emergence and expansion.

Contribution

It introduces the Neighboring Equilibrium Update method, significantly accelerating global gyrokinetic simulations and providing new insights into self-organized plasma structures.

Findings

Internal transport barrier forms at the magnetic axis due to turbulence avalanche.

Outward expansion of the barrier is a catastrophe of self-organization.

The method speeds up simulations by more than 10 times.

Abstract

Understanding the self-organization of the most promising internal transport barrier in fusion plasmas needs a long-time nonlinear gyrokinetic global simulation. The Neighboring Equilibrium Update method, which solves the secularity problem in a perturbative simulation and speeds up the numerical computation by more than 10 times. It is found that the internal transport barrier emerges at the magnetic axis due to inward propagated turbulence avalanche, and its outward expansion is the catastrophe of self-organized structure induced by outward propagated avalanche.