Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD

M. T. Beidler; J. D. Callen; C. C. Hegna; C. R. Sovinec

doi:10.1063/1.4982814

Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD

M. T. Beidler, J. D. Callen, C. C. Hegna, C. R. Sovinec

Research output: Contribution to journal › Article › peer-review

17 Scopus citations

Abstract

The nonlinear, extended-magnetohydrodynamic (MHD) code NIMROD is benchmarked with the theory of time-dependent forced magnetic reconnection induced by small resonant fields in slab geometry in the context of visco-resistive MHD modeling. Linear computations agree with time-asymptotic, linear theory of flow screening of externally applied fields. The inclusion of flow in nonlinear computations can result in mode penetration due to the balance between electromagnetic and viscous forces in the time-asymptotic state, which produces bifurcations from a high-slip state to a low-slip state as the external field is slowly increased. We reproduce mode penetration and unlocking transitions by employing time-dependent externally applied magnetic fields. Mode penetration and unlocking exhibit hysteresis and occur at different magnitudes of applied field. We also establish how nonlinearly determined flow screening of the resonant field is affected by the square of the magnitude of the externally applied field. These results emphasize that the inclusion of nonlinear physics is essential for accurate prediction of the reconnected field in a flowing plasma.

Original language	English
Article number	052508
Journal	Physics of Plasmas
Volume	24
Issue number	5
DOIs	https://doi.org/10.1063/1.4982814
State	Published - May 1 2017
Externally published	Yes

Funding

The first author would like to thank E. Howell, K. Bunkers, B. Cornille, and T. Bechtel for helpful discussions related to computation and visualization with NIMROD, and A. Becerra and D. Brennan for insightful discussion on underlying FMR physics. All the authors thank R. Nazikian for his experimentalist's perspective and motivation for these FMR studies. This research was supported in part by the U.S. Department of Energy (DOE), Office of Science, Office of Fusion Energy Sciences under Grant Nos. DE-FG02-92ER54139 and DE-FG02-86ER53218. The first author was also supported in part by the U.S. DOE Fusion Energy Sciences Postdoctoral Research Program administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by Oak Ridge Associated Universities (ORAU) under DOE Contract No. DE-SC0014664. All opinions expressed in this paper are the authors' and do not necessarily reflect the policies and views of DOE, ORAU, or ORISE.

Funders	Funder number
NIMROD
U.S. DOE Fusion Energy Sciences
U.S. Department of Energy
Office of Science
Fusion Energy Sciences	DE-FG02-92ER54139, DE-FG02-86ER53218
Oak Ridge Associated Universities	DE-SC0014664
Oak Ridge Institute for Science and Education

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title = "Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD",

abstract = "The nonlinear, extended-magnetohydrodynamic (MHD) code NIMROD is benchmarked with the theory of time-dependent forced magnetic reconnection induced by small resonant fields in slab geometry in the context of visco-resistive MHD modeling. Linear computations agree with time-asymptotic, linear theory of flow screening of externally applied fields. The inclusion of flow in nonlinear computations can result in mode penetration due to the balance between electromagnetic and viscous forces in the time-asymptotic state, which produces bifurcations from a high-slip state to a low-slip state as the external field is slowly increased. We reproduce mode penetration and unlocking transitions by employing time-dependent externally applied magnetic fields. Mode penetration and unlocking exhibit hysteresis and occur at different magnitudes of applied field. We also establish how nonlinearly determined flow screening of the resonant field is affected by the square of the magnitude of the externally applied field. These results emphasize that the inclusion of nonlinear physics is essential for accurate prediction of the reconnected field in a flowing plasma.",

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Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD

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