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Title: Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

Abstract

It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transportmore » is mediated by avalanche structures which propagate through the marginally stable regions.« less

Authors:
; ; ; ; ;  [1];  [2];  [3];  [4];  [5]
  1. Physics Department, University of Bayreuth, Universitätsstrasse 30, Bayreuth (Germany)
  2. Aix Marseille Univ, CNRS, PIIM, UMR 7345, Marseille (France)
  3. General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)
  4. CCFE, Culham Science Centre, Abingdon OX14 3DB, Oxon (United Kingdom)
  5. Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching (Germany)
Publication Date:
OSTI Identifier:
22599892
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPARATIVE EVALUATIONS; CYCLONES; HEAT; HEAT FLUX; ION TEMPERATURE; IONS; NONLINEAR PROBLEMS; SIMULATION; TEMPERATURE GRADIENTS; TRANSPORT THEORY; TUBES; TURBULENCE; WAVELENGTHS

Citation Formats

Peeters, A. G., Rath, F., Buchholz, R., Grosshauser, S. R., Strintzi, D., Weikl, A., Camenen, Y., Candy, J., Casson, F. J., and Hornsby, W. A.. Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold. United States: N. p., 2016. Web. doi:10.1063/1.4961231.
Peeters, A. G., Rath, F., Buchholz, R., Grosshauser, S. R., Strintzi, D., Weikl, A., Camenen, Y., Candy, J., Casson, F. J., & Hornsby, W. A.. Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold. United States. doi:10.1063/1.4961231.
Peeters, A. G., Rath, F., Buchholz, R., Grosshauser, S. R., Strintzi, D., Weikl, A., Camenen, Y., Candy, J., Casson, F. J., and Hornsby, W. A.. Mon . "Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold". United States. doi:10.1063/1.4961231.
@article{osti_22599892,
title = {Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold},
author = {Peeters, A. G. and Rath, F. and Buchholz, R. and Grosshauser, S. R. and Strintzi, D. and Weikl, A. and Camenen, Y. and Candy, J. and Casson, F. J. and Hornsby, W. A.},
abstractNote = {It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.},
doi = {10.1063/1.4961231},
journal = {Physics of Plasmas},
number = 8,
volume = 23,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}