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Title: Parallel electron force balance and the L-H transition

Abstract

In one popular description of the L-H transition, energy transfer to the mean flows directly depletes turbulence fluctuation energy, resulting in suppression of the turbulence and a corresponding transport bifurcation. However, electron parallel force balance couples nonzonal velocity fluctuations with electron pressure fluctuations on rapid timescales, comparable with the electron transit time. For this reason, energy in the nonzonal velocity stays in a fairly fixed ratio to the free energy in electron density fluctuations, at least for frequency scales much slower than electron transit. In order for direct depletion of the energy in turbulent fluctuations to cause the L-H transition, energy transfer via Reynolds stress must therefore drain enough energy to significantly reduce the sum of the free energy in nonzonal velocities and electron pressure fluctuations. At low k, the electron thermal free energy is much larger than the energy in nonzonal velocities, posing a stark challenge for this model of the L-H transition.

Creator(s)/Author(s):
Publication Date:
DOE Contract Number:  
AC02-09CH11466
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
U. S. Department of Energy
Keywords:
L-H transition; Tokamak; Reynolds stress; Zonal flows
OSTI Identifier:
1562067
DOI:
10.11578/1562067

Citation Formats

Stoltzfus-Dueck, T. Parallel electron force balance and the L-H transition. United States: N. p., 2016. Web. doi:10.11578/1562067.
Stoltzfus-Dueck, T. Parallel electron force balance and the L-H transition. United States. doi:10.11578/1562067.
Stoltzfus-Dueck, T. 2016. "Parallel electron force balance and the L-H transition". United States. doi:10.11578/1562067. https://www.osti.gov/servlets/purl/1562067. Pub date:Sun May 01 00:00:00 EDT 2016
@article{osti_1562067,
title = {Parallel electron force balance and the L-H transition},
author = {Stoltzfus-Dueck, T},
abstractNote = {In one popular description of the L-H transition, energy transfer to the mean flows directly depletes turbulence fluctuation energy, resulting in suppression of the turbulence and a corresponding transport bifurcation. However, electron parallel force balance couples nonzonal velocity fluctuations with electron pressure fluctuations on rapid timescales, comparable with the electron transit time. For this reason, energy in the nonzonal velocity stays in a fairly fixed ratio to the free energy in electron density fluctuations, at least for frequency scales much slower than electron transit. In order for direct depletion of the energy in turbulent fluctuations to cause the L-H transition, energy transfer via Reynolds stress must therefore drain enough energy to significantly reduce the sum of the free energy in nonzonal velocities and electron pressure fluctuations. At low k, the electron thermal free energy is much larger than the energy in nonzonal velocities, posing a stark challenge for this model of the L-H transition.},
doi = {10.11578/1562067},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2016},
month = {5}
}

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