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Title: Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

Abstract

Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux—$$\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $$ is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux $$\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $$ in strong electrostatic turbulence is calculated using the Hasegawa–Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.

Authors:
 [1];  [1];  [2]
  1. Huazhong University of Science and Technology, Wuhan (China). State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engneering
  2. University of California at San Diego, La Jolla, CA (United States). Center for Momentum Transport and Flow Organization and Center for Astrophysics and Space Sciences
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1290304
Alternate Identifier(s):
OSTI ID: 1290305; OSTI ID: 1429884
Grant/Contract Number:
FG02-04ER54738; 2013GB112002
Resource Type:
Journal Article: Published Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 10; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; poloidal rotation; nonlinear poloidal momentum flux; strong turbulence; Reynolds stress

Citation Formats

Wang, Lu, Wen, Tiliang, and Diamond, P. H. Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence. United States: N. p., 2016. Web. doi:10.1088/0029-5515/56/10/106017.
Wang, Lu, Wen, Tiliang, & Diamond, P. H. Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence. United States. doi:10.1088/0029-5515/56/10/106017.
Wang, Lu, Wen, Tiliang, and Diamond, P. H. Thu . "Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence". United States. doi:10.1088/0029-5515/56/10/106017.
@article{osti_1290304,
title = {Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence},
author = {Wang, Lu and Wen, Tiliang and Diamond, P. H.},
abstractNote = {Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux—$\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $ is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux $\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $ in strong electrostatic turbulence is calculated using the Hasegawa–Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.},
doi = {10.1088/0029-5515/56/10/106017},
journal = {Nuclear Fusion},
number = 10,
volume = 56,
place = {United States},
year = {Thu Aug 11 00:00:00 EDT 2016},
month = {Thu Aug 11 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1088/0029-5515/56/10/106017

Citation Metrics:
Cited by: 1work
Citation information provided by
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  • Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux—more » $$\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $$ is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux $$\langle {{\tilde{v}}_{r}}\tilde{n}{{\tilde{v}}_{\theta}}\rangle $$ in strong electrostatic turbulence is calculated using the Hasegawa–Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.« less
  • Most existing theoretical studies of momentum transport focus on calculating the Reynolds stress based on quasilinear theory, without considering the nonlinear momentum flux-〈v{sup ~}{sub r}n{sup ~}u{sup ~}{sub ∥}〉. However, a recent experiment on TORPEX found that the nonlinear toroidal momentum flux induced by blobs makes a significant contribution as compared to the Reynolds stress [Labit et al., Phys. Plasmas 18, 032308 (2011)]. In this work, the nonlinear parallel momentum flux in strong electrostatic turbulence is calculated by using a three dimensional Hasegawa-Mima equation, which is relevant for tokamak edge turbulence. It is shown that the nonlinear diffusivity is smaller thanmore » the quasilinear diffusivity from Reynolds stress. However, the leading order nonlinear residual stress can be comparable to the quasilinear residual stress, and so may be important to intrinsic rotation in tokamak edge plasmas. A key difference from the quasilinear residual stress is that parallel fluctuation spectrum asymmetry is not required for nonlinear residual stress.« less
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  • A significant inward flux of toroidal momentum is found in global gyrokinetic simulations of ion temperature gradient turbulence, leading to core plasma rotation spin-up. The underlying mechanism is identified to be the generation of residual stress due to the k{sub parallel} symmetry breaking induced by global quasistationary zonal flow shear. Simulations also show a significant off-diagonal element associated with the ion temperature gradient in the neoclassical momentum flux, while the overall neoclassical flux is small. In addition, the residual turbulence found in the presence of strong ExB flow shear may account for neoclassical-level ion heat and anomalous momentum transport widelymore » observed in experiments.« less