The anisotropic redistribution of free energy for gyrokinetic plasma turbulence in a Z-pinch

A. Bañón Navarro, Bogdan Teaca, F. Jenko

Research output: Contribution to journalArticle

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11 Downloads (Pure)

Abstract

For a Z-pinch geometry, we report on the nonlinear redistribution of free energy across scales perpendicular to the magnetic guide field, for a turbulent plasma described in the framework of gyrokinetics. The analysis is performed using a local flux-surface approximation, in a regime dominated by electrostatic fluctuations driven by the entropy mode, with both ion and electron species being treated kinetically. To explore the anisotropic nature of the free energy redistribution caused by the emergence of zonal flows, we use a polar coordinate representation for the field-perpendicular directions and define an angular density for the scale flux. Positive values for the classically defined (angle integrated) scale flux, which denote a direct energy cascade, are shown to be also composed of negative angular sections, a fact that impacts our understanding of the backscatter of energy and the way in which it enters the modeling of sub-grid scales for turbulence. A definition for the flux of free energy across each perpendicular direction is introduced as well, which shows that the redistribution of energy in the presence of zonal flows is highly anisotropic.
Original languageEnglish
Article number042301
JournalPhysics of Plasmas
Volume23
DOIs
Publication statusPublished - 2016

Fingerprint

plasma turbulence
free energy
polar coordinates
energy
cascades
turbulence
grids
entropy
electrostatics
geometry
approximation
ions
electrons

Bibliographical note

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
The following article appeared in Physics of Plasma and may be found at http://dx.doi.org/10.1063/1.4945633

Keywords

  • Free energy
  • Zonal flows
  • Plasma turbulence
  • Energy transfer
  • Z pinch

Cite this

The anisotropic redistribution of free energy for gyrokinetic plasma turbulence in a Z-pinch. / Bañón Navarro, A.; Teaca, Bogdan; Jenko, F.

In: Physics of Plasmas, Vol. 23, 042301, 2016.

Research output: Contribution to journalArticle

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