HR: 14:45h
AN: SM33A-06    [Abstracts]
TI: Reconnection via Thin Current Sheets in Earth's Magnetotail: Theory, Simulations and Cluster Observations
AU: * Sitnov, M I
EM: sitnov@umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, Energy Research Facility (Bldg. #223), Paint Branch Drive, College Park, MD 20742-35 United States
AU: Guzdar, P N
EM: guzdar@umd.edu
AF: Institute for Research in Electronics and Applied Physics, University of Maryland, Energy Research Facility (Bldg. #223), Paint Branch Drive, College Park, MD 20742-35 United States
AU: Swisdak, M M
AF: Naval Research Laboratory, 4555 Overlook Ave SW, Code 6794, Washington, DC 20375 United States
AB: Boundary perturbations of the magnetic field reversal region in plasma result in either the classical X-line reconnection or the formation of tangential discontinuities [Kulsrud and Hahm, 1982]. According to recent Geotail and Cluster observations, the latter scenario is likely to occur in the region earthward of X=-24Re due to the formation of the extended thin current sheet with the thickness comparable to a few thermal ion gyroradii. Within the framework of fluid theory, magnetic reconnection via current sheet is known to be very slow as compared to the X-line case. However, the structure and dynamics of thin current sheets in collisionless plasmas of the geomagnetotail is strongly influenced by the kinetic and nonlocal effects because the ion gyroradius is comparable to the current sheet thickness. Another important factor, which was not considered earlier in the theory, are large-scale flapping motions of the tail current sheet with the amplitude comparable to the current sheet thickness. We present the kinetic theory of thin current sheets, taking explicitly into account the kinetic effects arising from the complicated nonguiding center ion motion near the magnetic field reversal. It is shown, that, in contrast to the fluid theory, the kinetic effects allow fast reconnection even for very long current sheets. The predictions of the theory as well as particle simulations based on the new class of thin current sheets equilibria are compared with Cluster observations of atypical current sheets and their flapping motions as well as with other models predictions. The new theory and simulations are shown to explain the effect of flankward propagation of flapping waves as well as the north-south asymmetry of flapping sheets. Reference: R. M. Kulsrud and T. S. Hahm, Forced magnetic reconnection. Phys. Scripta, v. T2/2, p.525, 1982.
DE: 2744 Magnetotail
DE: 7827 Kinetic and MHD theory
DE: 7835 Magnetic reconnection
SC: SPA-Magnetospheric Physics [SM]
MN: 2005 Joint Assembly