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Title: Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field

Abstract

Here, negative compressibility ITG turbulence in a linear plasma device (CSDX) can induce a negative viscosity increment. However, even with this negative increment, we show that the total axial viscosity remains positive definite, i.e. no intrinsic axial flow can be generated by pure ITG turbulence in a straight magnetic field. This differs from the case of electron drift wave (EDW) turbulence, where the total viscosity can turn negative, at least transiently. When the flow gradient is steepened by any drive mechanism, so that the parallel shear flow instability (PSFI) exceeds the ITG drive, the flow profile saturates at a level close to the value above which PSFI becomes dominant. This saturated flow gradient exceeds the PSFI linear threshold, and grows with $$\nabla T_{i0}$$ as $$|\nabla V_\parallel| / |k_\parallel c_s| \sim|\nabla T_{i0}|^{2/3} / (k_\parallel T_{i0})^{2/3}$$. This scaling trend characterizes the effective stiffness of the parallel flow gradient.

Authors:
ORCiD logo;
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1346872
Alternate Identifier(s):
OSTI ID: 1348956
Grant/Contract Number:  
FG02-04ER54738
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 3; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Li, J. C., and Diamond, P. H. Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field. United States: N. p., 2017. Web. doi:10.1063/1.4978956.
Li, J. C., & Diamond, P. H. Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field. United States. doi:10.1063/1.4978956.
Li, J. C., and Diamond, P. H. Thu . "Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field". United States. doi:10.1063/1.4978956. https://www.osti.gov/servlets/purl/1346872.
@article{osti_1346872,
title = {Negative viscosity from negative compressibility and axial flow shear stiffness in a straight magnetic field},
author = {Li, J. C. and Diamond, P. H.},
abstractNote = {Here, negative compressibility ITG turbulence in a linear plasma device (CSDX) can induce a negative viscosity increment. However, even with this negative increment, we show that the total axial viscosity remains positive definite, i.e. no intrinsic axial flow can be generated by pure ITG turbulence in a straight magnetic field. This differs from the case of electron drift wave (EDW) turbulence, where the total viscosity can turn negative, at least transiently. When the flow gradient is steepened by any drive mechanism, so that the parallel shear flow instability (PSFI) exceeds the ITG drive, the flow profile saturates at a level close to the value above which PSFI becomes dominant. This saturated flow gradient exceeds the PSFI linear threshold, and grows with $\nabla T_{i0}$ as $|\nabla V_\parallel| / |k_\parallel c_s| \sim|\nabla T_{i0}|^{2/3} / (k_\parallel T_{i0})^{2/3}$. This scaling trend characterizes the effective stiffness of the parallel flow gradient.},
doi = {10.1063/1.4978956},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 3,
volume = 24,
place = {United States},
year = {2017},
month = {3}
}

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