Statistical Analysis of Plasma Dynamics in Gyrokinetic Simulations of Stellarator Turbulence

Aristeides D. Papadopoulos, Johan Anderson, Eun-jin Kim, Michail Mavridis, Heinz Isliker

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Abstract

A geometrical method for assessing stochastic processes in plasma turbulence is investi- gated in this study. The thermodynamic length methodology allows using a Riemannian metric on the phase space; thus, distances between thermodynamic states can be computed. It constitutes a geometric methodology to understand stochastic processes involved in, e.g., order–disorder tran- sitions, where a sudden increase in distance is expected. We consider gyrokinetic simulations of ion-temperature-gradient (ITG)-mode-driven turbulence in the core region of the stellarator W7-X with realistic quasi-isodynamic topologies. In gyrokinetic plasma turbulence simulations, avalanches, e.g., of heat and particles, are often found, and in this work, a novel method for detection is inves- tigated. This new method combines the singular spectrum analysis algorithm with a hierarchical clustering method such that the time series is decomposed into two parts: useful physical information and noise. The informative component of the time series is used for the calculation of the Hurst exponent, the information length, and the dynamic time. Based on these measures, the physical properties of the time series are revealed.
Original languageEnglish
Article number942
Number of pages21
JournalEntropy
Volume25
Issue number6
Early online date15 Jun 2023
DOIs
Publication statusPublished - 15 Jun 2023

Bibliographical note

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Funder

This work was carried out within the framework of the EUROfusion Consortium and received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

Keywords

  • gyrokinetic simulations
  • drift waves
  • stochastic theory
  • information geometry
  • time series analysis

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