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Title: Extended MHD modeling of tearing-driven magnetic relaxation

Discrete relaxation events in reversed-field pinch relevant configurations are investigated numerically with nonlinear extended magnetohydrodynamic modeling, including the Hall term in Ohm’s law and first-order ion finite Larmor radius effects. Our results show variability among relaxation events, where the Hall dynamo effect may help or impede the MHD dynamo effect in relaxing the parallel current density profile. The competitive behavior arises from multi-helicity conditions where the dominant magnetic fluctuation is relatively small. The resulting changes in parallel current density and parallel flow are aligned in the core, consistent with experimental observations. Analysis of simulation results also confirms that force density from fluctuation-induced Reynolds stress arises subsequent to the drive from fluctuation-induced Lorentz force density. Transport of momentum density is found to be dominated by the fluctuation-induced Maxwell stress over most of the cross section with viscous and gyroviscous contributions being large in the edge region. The findings resolve a discrepancy with respect to the relative orientation of current density and flow relaxation, which had not been realized or investigated in Ref. [King et. al. Phys. Plasmas 19, 055905 (2012)], where only the magnitude of flow relaxation is actually consistent with experimental results.
Authors:
ORCiD logo [1] ;  [2]
  1. Univ. of Wisconsin, Madison, WI (United States). Center for Plasma Theory and Computation and Dept. of Physics; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Wisconsin, Madison, WI (United States). Center for Plasma Theory and Dept. of Engineering-Physics
Publication Date:
Grant/Contract Number:
FG02-06ER54850; PHY-0821899; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Wisconsin, Madison, WI (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Lorentz group; plasma flows; reversed field pinch; magnetohydrodynamics; current density; viscosity; Reynolds stress modeling; parallel processing; electric fields; magnetic fields
OSTI Identifier:
1461732
Alternate Identifier(s):
OSTI ID: 1348031

Sauppe, J. P., and Sovinec, C. R.. Extended MHD modeling of tearing-driven magnetic relaxation. United States: N. p., Web. doi:10.1063/1.4977540.
Sauppe, J. P., & Sovinec, C. R.. Extended MHD modeling of tearing-driven magnetic relaxation. United States. doi:10.1063/1.4977540.
Sauppe, J. P., and Sovinec, C. R.. 2017. "Extended MHD modeling of tearing-driven magnetic relaxation". United States. doi:10.1063/1.4977540. https://www.osti.gov/servlets/purl/1461732.
@article{osti_1461732,
title = {Extended MHD modeling of tearing-driven magnetic relaxation},
author = {Sauppe, J. P. and Sovinec, C. R.},
abstractNote = {Discrete relaxation events in reversed-field pinch relevant configurations are investigated numerically with nonlinear extended magnetohydrodynamic modeling, including the Hall term in Ohm’s law and first-order ion finite Larmor radius effects. Our results show variability among relaxation events, where the Hall dynamo effect may help or impede the MHD dynamo effect in relaxing the parallel current density profile. The competitive behavior arises from multi-helicity conditions where the dominant magnetic fluctuation is relatively small. The resulting changes in parallel current density and parallel flow are aligned in the core, consistent with experimental observations. Analysis of simulation results also confirms that force density from fluctuation-induced Reynolds stress arises subsequent to the drive from fluctuation-induced Lorentz force density. Transport of momentum density is found to be dominated by the fluctuation-induced Maxwell stress over most of the cross section with viscous and gyroviscous contributions being large in the edge region. The findings resolve a discrepancy with respect to the relative orientation of current density and flow relaxation, which had not been realized or investigated in Ref. [King et. al. Phys. Plasmas 19, 055905 (2012)], where only the magnitude of flow relaxation is actually consistent with experimental results.},
doi = {10.1063/1.4977540},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {2017},
month = {3}
}

Works referenced in this record:

Time-Resolved Observation of Discrete and Continuous Magnetohydrodynamic Dynamo in the Reversed-Field Pinch Edge
journal, August 1994