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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 13, 1712, doi:10.1029/2003GL017218, 2003

A model of the bifurcated current sheet

M. I. Sitnov

Department of Astronomy, University of Maryland,
College Park, Maryland, USA


Also at Skobeltsyn Institute of Nuclear Physics, Moscow State University,
Moscow, Russia

P. N. Guzdar and M. Swisdak

Institute for Research in Electronics and Applied Physics, University of Maryland,
College Park, Maryland, USA

Abstract

[1]   Recent Geotail and Cluster observations revealed that thin current sheets in the near-Earth tail may have a bifurcated structure. In some cases the electrons are found to dominate the current. We present a generalization of the Harris current sheet equilibrium, which reproduces these features. The model ion distribution contains an additional element, viz. the quasi-adiabatic invariant of the ion motion across the sheet, and assumes ion temperature anisotropy outside the sheet. Bifurcated current sheets appear in the case of small ion anisotropy with Tperpendicular toi > T||i (pancake distributions). In the opposite case (cigar distributions) the model describes a single-peaked ion-dominated current sheet embedded in a thicker Harris sheet, which is more relevant to the outflow region of the collisionless reconnection pattern in the deHoffman-Teller frame.

Received 27 February 2003; revised 28 April 2003; accepted 5 June 2003; published 12 July 2003.

Index Terms: 2744 Magnetospheric Physics: Magnetotail; 7827 Space Plasma Physics: Kinetic and MHD theory; 7835 Space Plasma Physics: Magnetic reconnection.

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Citation: Sitnov, M. I., P. N. Guzdar, and M. Swisdak, A model of the bifurcated current sheet, Geophys. Res. Lett., 30(13), 1712, doi:10.1029/2003GL017218, 2003.