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Energy Transfer and Dissipation in Plasma Turbulence

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Dear Colleagues,

In neutral fluids and in plasma flows, the ubiquitous presence of nonlinear interactions can lead to the development of turbulence. Turbulence is often characterized by energetic couplings between different scales of flows. This Special Issue aims at collecting current state-of-the-art modeling efforts of turbulence in, e.g., fluids and plasmas and other related fields. The areas of interests are statistical methods, including investigations on entropy and information length, uncertainty quantification, and data-driven or machine learning modeling and theoretical models accounting for or contributing to the understanding of the multiscale problem in turbulence; methods addressing intermittency, coherent structures, and self-organization are also welcome. Another area of interest is the coupling of phases and synchronization in turbulence. The Guest Editor is open to considering any paper relevant to the subject matter of the Special Issue.

Dr. Johan Anderson
Guest Editor

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Keywords

fluid dynamics
plasma physics
energy transfer
phase synchronization
entropy
information length
statistical mechanics
intermittency
coherent structures
multiscale analysis
self-organization
probability distribution functions
extreme events

Published Papers (3 papers)

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Research

21 pages, 3111 KiB

Open AccessFeature PaperArticle

Electromagnetic Conversion into Kinetic and Thermal Energies

by Axel Brandenburg and Nousaba Nasrin Protiti

Entropy 2023, 25(9), 1270; https://doi.org/10.3390/e25091270 - 29 Aug 2023

Viewed by 1193

Abstract

The conversion of electromagnetic energy into magnetohydrodynamic energy occurs when the electric conductivity changes from negligible to finite values. This process is relevant during the epoch of reheating in the early universe at the end of inflation and before the emergence of the radiation-dominated era. We find that the conversion into kinetic and thermal energies is primarily the result of electric energy dissipation, while magnetic energy only plays a secondary role in this process. This means that since electric energy dominates over magnetic energy during inflation and reheating, significant amounts of electric energy can be converted into magnetohydrodynamic energy when conductivity emerges before the relevant length scales become stable. Full article

(This article belongs to the Special Issue Energy Transfer and Dissipation in Plasma Turbulence)

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21 pages, 2415 KiB

Open AccessFeature PaperArticle

Statistical Analysis of Plasma Dynamics in Gyrokinetic Simulations of Stellarator Turbulence

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

Entropy 2023, 25(6), 942; https://doi.org/10.3390/e25060942 - 15 Jun 2023

Viewed by 906

Abstract

A geometrical method for assessing stochastic processes in plasma turbulence is investigated 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 transitions, 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 investigated. 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. Full article

(This article belongs to the Special Issue Energy Transfer and Dissipation in Plasma Turbulence)

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19 pages, 34416 KiB

Open AccessArticle

Effects of Stochastic Noises on Limit-Cycle Oscillations and Power Losses in Fusion Plasmas and Information Geometry

by Rainer Hollerbach and Eun-jin Kim

Entropy 2023, 25(4), 664; https://doi.org/10.3390/e25040664 - 15 Apr 2023

Viewed by 1189

Abstract

We investigate the effects of different stochastic noises on the dynamics of the edge-localised modes (ELMs) in magnetically confined fusion plasmas by using a time-dependent PDF method, path-dependent information geometry (information rate, information length), and entropy-related measures (entropy production, mutual information). The oscillation quenching occurs due to either stochastic particle or magnetic perturbations, although particle perturbation is more effective in this amplitude diminishment compared with magnetic perturbations. On the other hand, magnetic perturbations are more effective at altering the oscillation period; the stochastic noise acts to increase the frequency of explosive oscillations (large ELMs) while decreasing the frequency of more regular oscillations (small ELMs). These stochastic noises significantly reduce power and energy losses caused by ELMs and play a key role in reproducing the observed experimental scaling relation of the ELM power loss with the input power. Furthermore, the maximum power loss is closely linked to the maximum entropy production rate, involving irreversible energy dissipation in non-equilibrium. Notably, over one ELM cycle, the information rate appears to keep almost a constant value, indicative of a geodesic. The information rate is also shown to be useful for characterising the statistical properties of ELMs, such as distinguishing between explosive and regular oscillations and the regulation between the pressure gradient and magnetic fluctuations. Full article

(This article belongs to the Special Issue Energy Transfer and Dissipation in Plasma Turbulence)

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