HR: 1340h
AN: SM53B-0417    [Abstracts]
TI: Externally Driven Magnetic Reconnection in the Presence of a Normal Magnetic Field
AU: Coroniti, F V
EM: coroniti@astro.ucla.edu
AF: Department of Physics and Astronomy, University of California, 405 Hilgard Avenue, Los Angeles, CA 90095-1547 United States
AU: * Pritchett, P L
EM: pritchet@physics.ucla.edu
AF: Department of Physics and Astronomy, University of California, 405 Hilgard Avenue, Los Angeles, CA 90095-1547 United States
AB: The possibility that the collisionless tearing instability could explain the sudden onset of magnetic reconnection associated with the expansion phase of substorms in the terrestrial magnetotail has been the subject of extensive investigation. Two-dimensional treatments have generally concluded that such a spontaneous instability is not possible due to the stabilizing compressibility effects associated with the electron response to the tearing perturbation. In the magnetotail, however, reconnection typically occurs in configurations that have evolved under driving by a convection electric field imposed by the solar wind and which may feature structure in the east-west direction. A massively-parallel 3D PIC code is used to study the evolution of a plasma-sheet configuration under the influence of such a driving field. The simulations start from a moderately thick current sheet whose half width is $1.6 c/ \omega_{pi}$ and which is only weakly unstable to the lower hybrid drift and drift kink instabilities. Imposition of the driving electric field leads to thinning of the current sheet as a result of the formation of an embedded electron current structure; the half width is reduced to as little as $\sim 0.4 c/\omega_{pi}$. Once the local $B_z$ field is driven through zero, rapid reconnection ensues, leading to the formation of a large island. No evidence of strong excitation of finite-$k_y$ modes is observed, although the outflow regions do develop an interchange-like structure in the equatorial plane. It appears that the reconnection produced by a continuous external driver in a 2D normal field configuration plasma sheet is basically similar to that in a 1D current sheet.
DE: 7835 Magnetic reconnection
DE: 7843 Numerical simulation studies
DE: 2744 Magnetotail
DE: 2764 Plasma sheet
DE: 2772 Plasma waves and instabilities
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting