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Title: Global axisymmetric simulations of two-fluid reconnection in an experimentally relevant geometry

Abstract

To address the interplay between local and global effects in magnetic reconnection, axisymmetric numerical simulations for the Magnetic Reconnection Experiment [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)] are performed using the NIMROD code [C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. The 'pull' and 'push' modes of the device are simulated both with and without two-fluid effects in the generalized Ohm's law. As in experiment, the pull reconnection rate is slowed due to the presence of downstream pressure associated with the outflow. Effects induced by toroidicity include a radially inward drift of the current sheet during pull reconnection and a radially outward displacement of the X-point during push reconnection. These effects result from the inboard side of the current sheet having less volume than the outboard side, facilitating the formation of large scale pressure gradients since the inboard side is more susceptible to a buildup or depletion of density. Toroidicity also leads to asymmetry of the quadrupole field during two-fluid simulations. During pull reconnection, the outboard lobes of the quadrupole typically peak close to the X-point, whereas the inboard quadrupole lobes peak near the flux core surfaces. At experimentally relevant parameters, the reconnection rate ismore » found to depend more on the mode of operation than on the inclusion of two-fluid effects. The current sheet in two-fluid co-helicity simulations tilts due to a Lorentz force associated with the guide field and the outflowing electrons, resulting in asymmetric flow patterns for both ions and electrons. In two-fluid counter-helicity simulations, the Hall effect leads to a radial shift in position of the X-point and an asymmetric outflow pattern, which is examined in terms of separate force-density contributions. In general, asymmetry due to toroidicity or the Hall effect often leads to uneven outflow, which then feeds back on the reconnection process through large scale pressure gradients.« less

Authors:
 [1];  [2]
  1. Department of Astronomy, University of Wisconsin, Madison, Wisconsin 53706 (United States)
  2. Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, Wisconsin 53706 (United States)
Publication Date:
OSTI Identifier:
21120245
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 15; Journal Issue: 4; Other Information: DOI: 10.1063/1.2904600; (c) 2008 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:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASYMMETRY; AXIAL SYMMETRY; CURRENTS; ELECTRONS; FLUIDS; GEOMETRY; HALL EFFECT; HELICITY; LORENTZ FORCE; MAGNETIC RECONNECTION; MAGNETOHYDRODYNAMICS; OHM LAW; PLASMA; PLASMA SIMULATION; PRESSURE GRADIENTS; QUADRUPOLES

Citation Formats

Murphy, N A, Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, Wisconsin 53706, Sovinec, C R, and Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706. Global axisymmetric simulations of two-fluid reconnection in an experimentally relevant geometry. United States: N. p., 2008. Web. doi:10.1063/1.2904600.
Murphy, N A, Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, Wisconsin 53706, Sovinec, C R, & Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706. Global axisymmetric simulations of two-fluid reconnection in an experimentally relevant geometry. United States. https://doi.org/10.1063/1.2904600
Murphy, N A, Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, Wisconsin 53706, Sovinec, C R, and Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706. 2008. "Global axisymmetric simulations of two-fluid reconnection in an experimentally relevant geometry". United States. https://doi.org/10.1063/1.2904600.
@article{osti_21120245,
title = {Global axisymmetric simulations of two-fluid reconnection in an experimentally relevant geometry},
author = {Murphy, N A and Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, Wisconsin 53706 and Sovinec, C R and Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706},
abstractNote = {To address the interplay between local and global effects in magnetic reconnection, axisymmetric numerical simulations for the Magnetic Reconnection Experiment [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)] are performed using the NIMROD code [C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. The 'pull' and 'push' modes of the device are simulated both with and without two-fluid effects in the generalized Ohm's law. As in experiment, the pull reconnection rate is slowed due to the presence of downstream pressure associated with the outflow. Effects induced by toroidicity include a radially inward drift of the current sheet during pull reconnection and a radially outward displacement of the X-point during push reconnection. These effects result from the inboard side of the current sheet having less volume than the outboard side, facilitating the formation of large scale pressure gradients since the inboard side is more susceptible to a buildup or depletion of density. Toroidicity also leads to asymmetry of the quadrupole field during two-fluid simulations. During pull reconnection, the outboard lobes of the quadrupole typically peak close to the X-point, whereas the inboard quadrupole lobes peak near the flux core surfaces. At experimentally relevant parameters, the reconnection rate is found to depend more on the mode of operation than on the inclusion of two-fluid effects. The current sheet in two-fluid co-helicity simulations tilts due to a Lorentz force associated with the guide field and the outflowing electrons, resulting in asymmetric flow patterns for both ions and electrons. In two-fluid counter-helicity simulations, the Hall effect leads to a radial shift in position of the X-point and an asymmetric outflow pattern, which is examined in terms of separate force-density contributions. In general, asymmetry due to toroidicity or the Hall effect often leads to uneven outflow, which then feeds back on the reconnection process through large scale pressure gradients.},
doi = {10.1063/1.2904600},
url = {https://www.osti.gov/biblio/21120245}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 4,
volume = 15,
place = {United States},
year = {Tue Apr 15 00:00:00 EDT 2008},
month = {Tue Apr 15 00:00:00 EDT 2008}
}