HR: 15:10h
AN: SH43A-07    [Abstracts]
TI: Collisionless Magnetic Reconnection in an Asymmetric Current Sheet: Implications for Magnetopause Reconnection
AU: * Pritchett, P L
EM: pritchet@physics.ucla.edu
AF: Department of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1547, United States
AB: Reconnection at the magnetopause probes several aspects of basic reconnection physics that are not duplicated elsewhere in the magnetosphere. At the magnetopause, reconnection occurs between two topologically distinct regions, the shocked solar wind and the magnetosphere, which have quite different properties (plasma density, plasma temperature, and magnetic field strength). Thus the standard symmetric Harris current sheet equilibrium is not well-suited for investigating magnetopause reconnection. Two-dimensional particle-in-cell simulations are used to probe reconnection in an asymmetric current sheet with a strong density gradient and unequal asymptotic magnetic field strengths. The starting configuration is a fluid equilibrium with overall pressure balance. This basic configuration is well maintained on average in the kinetic treatment, but the detailed structure at the center of the sheet is altered: a relatively strong E_x electric field forms on the high-field side of the layer to help confine the ions, the electron and ion drifts are not simply related by the temperature ratio, and the electrons dominate the current density in a thin region near the center of the current layer where the density gradient is strongest. Initial-value simulations of reconnection in this asymmetric layer produce smaller reconnection rates and lower saturation levels than for the symmetric case. If the asymmetric layer is subject to driving by an externally-imposed electric field, then an extended interval of quasi-steady reconnection is observed, which leads to larger islands. The effects of varying the magnetic shear angle across the layer will be reported.
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2724 Magnetopause and boundary layers
DE: 7833 Mathematical and numerical techniques (0500, 3200)
DE: 7835 Magnetic reconnection (2723, 7526)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting