Affiliation:
1. Fluid and Complex System Research Centre, Coventry University, Coventry CV1 2TT, UK
2. Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT, UK
Abstract
Magnetically confined plasmas are far from equilibrium and pose considerable challenges in statistical analysis. We discuss a non-perturbative statistical method, namely a time-dependent probability density function (PDF) approach that is potentially useful for analysing time-varying, large, or non-Gaussian fluctuations and bursty events associated with instabilities in the low-to-high confinement transition and the H-mode. Specifically, we present a stochastic Langevin model of edge-localized modes (ELMs) by including stochastic noise terms in a previous ODE ELM model. We calculate exact time-dependent PDFs by numerically solving the Fokker–Planck equation and characterize time-varying statistical properties of ELMs for different energy fluxes and noise amplitudes. The stochastic noise is shown to introduce phase-mixing and plays a significant role in mitigating extreme bursts of large ELMs. Furthermore, based on time-dependent PDFs, we provide a path-dependent information geometric theory of the ELM dynamics and demonstrate its utility in capturing self-regulatory relaxation oscillations, bursts and a sudden change in the system.This article is part of a discussion meeting issue ‘H-mode transition and pedestal studies in fusion plasmas’.
Subject
General Physics and Astronomy,General Engineering,General Mathematics
Cited by
2 articles.
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