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Title: First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch

Abstract

Drift and Hall effects on magnetic tearing, island evolution, and relaxation in pinch configurations are investigated using a non-reduced first-order finite-Larmor-radius (FLR) fluid model with the nonideal magnetohydrodynamics (MHD) with rotation, open discussion (NIMROD) code [C.R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)]. An unexpected result with a uniform pressure profile is a drift effect that reduces the growth rate when the ion sound gyroradius ({rho}{sub s}) is smaller than the tearing-layer width. This drift is present only with warm-ion FLR modeling, and analytics show that it arises from {nabla}B and poloidal curvature represented in the Braginskii gyroviscous stress. Nonlinear single-helicity computations with experimentally relevant {rho}{sub s} values show that the warm-ion gyroviscous effects reduce saturated-island widths. Computations with multiple nonlinearly interacting tearing fluctuations find that m = 1 core-resonant-fluctuation amplitudes are reduced by a factor of two relative to single-fluid modeling by the warm-ion effects. These reduced core-resonant-fluctuation amplitudes compare favorably to edge coil measurements in the Madison Symmetric Torus (MST) reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. The computations demonstrate that fluctuations induce both MHD- and Hall-dynamo emfs during relaxation events. The presence of a Hall-dynamo emf implies amore » fluctuation-induced Maxwell stress, and the simulation results show net transport of parallel momentum. The computed magnitude of force densities from the Maxwell and competing Reynolds stresses, and changes in the parallel flow profile, are qualitatively and semi-quantitatively similar to measurements during relaxation in MST.« less

Authors:
 [1];  [2];  [1]
  1. Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706 (United States)
  2. Department of Engineering-Physics, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States)
Publication Date:
OSTI Identifier:
22072375
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMPLITUDES; CALCULATION METHODS; FLOW MODELS; FLUCTUATIONS; IONS; LARMOR RADIUS; MAGNETOHYDRODYNAMICS; MST DEVICE; NIMROD; NONLINEAR PROBLEMS; PLASMA; PLASMA SIMULATION; RELAXATION; REVERSE-FIELD PINCH; REYNOLDS NUMBER; ROTATION; SOUND WAVES; STRESSES

Citation Formats

King, J R, Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303, Sovinec, C R, and Mirnov, V V. First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch. United States: N. p., 2012. Web. doi:10.1063/1.3695346.
King, J R, Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303, Sovinec, C R, & Mirnov, V V. First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch. United States. doi:10.1063/1.3695346.
King, J R, Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303, Sovinec, C R, and Mirnov, V V. Tue . "First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch". United States. doi:10.1063/1.3695346.
@article{osti_22072375,
title = {First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch},
author = {King, J R and Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303 and Sovinec, C R and Mirnov, V V},
abstractNote = {Drift and Hall effects on magnetic tearing, island evolution, and relaxation in pinch configurations are investigated using a non-reduced first-order finite-Larmor-radius (FLR) fluid model with the nonideal magnetohydrodynamics (MHD) with rotation, open discussion (NIMROD) code [C.R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)]. An unexpected result with a uniform pressure profile is a drift effect that reduces the growth rate when the ion sound gyroradius ({rho}{sub s}) is smaller than the tearing-layer width. This drift is present only with warm-ion FLR modeling, and analytics show that it arises from {nabla}B and poloidal curvature represented in the Braginskii gyroviscous stress. Nonlinear single-helicity computations with experimentally relevant {rho}{sub s} values show that the warm-ion gyroviscous effects reduce saturated-island widths. Computations with multiple nonlinearly interacting tearing fluctuations find that m = 1 core-resonant-fluctuation amplitudes are reduced by a factor of two relative to single-fluid modeling by the warm-ion effects. These reduced core-resonant-fluctuation amplitudes compare favorably to edge coil measurements in the Madison Symmetric Torus (MST) reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. The computations demonstrate that fluctuations induce both MHD- and Hall-dynamo emfs during relaxation events. The presence of a Hall-dynamo emf implies a fluctuation-induced Maxwell stress, and the simulation results show net transport of parallel momentum. The computed magnitude of force densities from the Maxwell and competing Reynolds stresses, and changes in the parallel flow profile, are qualitatively and semi-quantitatively similar to measurements during relaxation in MST.},
doi = {10.1063/1.3695346},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 19,
place = {United States},
year = {2012},
month = {5}
}