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Title: The substorm current wedge and field-aligned currents in MHD simulations of magnetotail reconnection

Abstract

The authors present results of a three-dimensional MHD simulation of magnetotail reconnection, which, in contrast to earlier ones, starts from an equilibrium configuration that contains a region 1 type field-aligned current system at the plasma sheet/lobe boundary. As in earlier simulations, the dynamic evolution develops from a slow diffusion to the fast growth of a three-dimensional tearing mode, initiated by the sudden occurrence or increase of resistivity, leading again to the formation and subsequent tailward ejection of a plasmoid, associated with fast plasma flows. In addition, they find changes of the electric current system which are consistent with the substorm current wedge picture inferred from observations, i.e., a deviation of cross-tail current from a near-Earth tail region toward the Earth on the dawn side and away on the dusk side, associated with field-aligned currents of the same signature. While the total cross-tail current is reduced at the location of the near-Earth reconnection site, the local current density at the near-Earth X line actually increases, consistent with the strong plasma sheet thinning in that region. The source regions of the field-aligned currents. indicated by strong peaks of {nabla}{center dot} j {parallel}, are identified as regions of strong plasma flow vorticity nearmore » the boundaries of the fast earthward flow earthward of the reconnection site. This flow shear increases preexisting magnetic shear resulting in an increased twist of magnetic flux tubes connected with these regions and thus a generation or increase of the field-aligned currents. They note that the current diversion in their simulation is not caused by a locally enhanced resistivity (although in reality this might be the case) but by the localization of reconnection in a three-dimensional tail configuration.« less

Authors:
;  [1]
  1. Los Alamos National Lab., NM (USA)
Publication Date:
OSTI Identifier:
5257633
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research; (United States)
Additional Journal Information:
Journal Volume: 96:A2; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MAGNETIC RECONNECTION; COMPUTERIZED SIMULATION; MAGNETOTAIL; CURRENT DENSITY; DIFFUSION; ELECTRIC CURRENTS; IONOSPHERE; MAGNETIC BAYS; PLASMA SHEET; PLASMOIDS; SOLAR WIND; TEARING INSTABILITY; THREE-DIMENSIONAL CALCULATIONS; CURRENTS; EARTH ATMOSPHERE; EARTH MAGNETOSPHERE; INSTABILITY; PLANETARY IONOSPHERES; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; SIMULATION; SOLAR ACTIVITY; 640201* - Atmospheric Physics- Auroral, Ionospheric, & Magetospheric Phenomena

Citation Formats

Birn, J, and Hesse, M. The substorm current wedge and field-aligned currents in MHD simulations of magnetotail reconnection. United States: N. p., 1991. Web. doi:10.1029/90JA01762.
Birn, J, & Hesse, M. The substorm current wedge and field-aligned currents in MHD simulations of magnetotail reconnection. United States. https://doi.org/10.1029/90JA01762
Birn, J, and Hesse, M. 1991. "The substorm current wedge and field-aligned currents in MHD simulations of magnetotail reconnection". United States. https://doi.org/10.1029/90JA01762.
@article{osti_5257633,
title = {The substorm current wedge and field-aligned currents in MHD simulations of magnetotail reconnection},
author = {Birn, J and Hesse, M},
abstractNote = {The authors present results of a three-dimensional MHD simulation of magnetotail reconnection, which, in contrast to earlier ones, starts from an equilibrium configuration that contains a region 1 type field-aligned current system at the plasma sheet/lobe boundary. As in earlier simulations, the dynamic evolution develops from a slow diffusion to the fast growth of a three-dimensional tearing mode, initiated by the sudden occurrence or increase of resistivity, leading again to the formation and subsequent tailward ejection of a plasmoid, associated with fast plasma flows. In addition, they find changes of the electric current system which are consistent with the substorm current wedge picture inferred from observations, i.e., a deviation of cross-tail current from a near-Earth tail region toward the Earth on the dawn side and away on the dusk side, associated with field-aligned currents of the same signature. While the total cross-tail current is reduced at the location of the near-Earth reconnection site, the local current density at the near-Earth X line actually increases, consistent with the strong plasma sheet thinning in that region. The source regions of the field-aligned currents. indicated by strong peaks of {nabla}{center dot} j {parallel}, are identified as regions of strong plasma flow vorticity near the boundaries of the fast earthward flow earthward of the reconnection site. This flow shear increases preexisting magnetic shear resulting in an increased twist of magnetic flux tubes connected with these regions and thus a generation or increase of the field-aligned currents. They note that the current diversion in their simulation is not caused by a locally enhanced resistivity (although in reality this might be the case) but by the localization of reconnection in a three-dimensional tail configuration.},
doi = {10.1029/90JA01762},
url = {https://www.osti.gov/biblio/5257633}, journal = {Journal of Geophysical Research; (United States)},
issn = {0148-0227},
number = ,
volume = 96:A2,
place = {United States},
year = {1991},
month = {2}
}