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

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01762· OSTI ID:5257633

Birn, J; Hesse, M ^[1]

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1. Los Alamos National Lab., NM (USA)

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.

• OSTI ID: 5257633
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A2; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMPUTERIZED SIMULATION
CURRENT DENSITY
CURRENTS
DIFFUSION
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
INSTABILITY
IONOSPHERE
MAGNETIC BAYS
MAGNETIC RECONNECTION
MAGNETOTAIL
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA SHEET
PLASMOIDS
SIMULATION
SOLAR ACTIVITY
SOLAR WIND
TEARING INSTABILITY
THREE-DIMENSIONAL CALCULATIONS