HR: 11:05h
AN: SM12A-04    [Abstracts]
TI: On the IMF clock angle dependence of the dayside magnetopause reconnection rate
AU: * Dorelli, J C
EM: john.dorelli@unh.edu
AF: University of New Hampshire, Morse Hall 245E, Durham, NH 03801
AU: Raeder, J
EM: J.Raeder@unh.edu
AF: University of New Hampshire, Morse Hall 245E, Durham, NH 03801
AB: We investigate the IMF clock angle dependence of steady magnetic reconnection at Earth's dayside magnetopause. We present results from a series of high resolution global resistive magnetohydrodynamics simulations (64 million computational cells, giving a magnetopause cell size of a couple hundred kilometers in the GSE X coordinate and about five hundred kilometers in the GSE Y and Z coordinates) in which the IMF clock angle is varied between 0 and 180 degrees. In order to make contact with analytic solutions of the resistive MHD equations (Sonnerup and Priest, J. Plasma Phys., 14, 283, 1975), constant plasma resistivity was used in all of the simulations. Although the reconnection topology has a global structure comprising magnetic nulls and associated separatrix surfaces, and involving the entire Chapman-Ferraro current sheet (we argue that this global current sheet is the 3D analogue of the 2D Sweet-Parker current sheet which results from the collapse of an X-type separator line), we focus our attention on the reconnection electric field at the subsolar point. We demonstrate that the reconnection rate is nonvanishing for all nonvanishing clock angles, in contrast to the predictions of the Sonnerup (JGR, 79, 1546, 1974) component reconnection model, in which there is a critical IMF clock angle below which reconnection is geometrically precluded). Further, and also in contrast to the Sonnerup (JGR, 79, 1546, 1974) model, the direction of the subsolar X line is not, in general, parallel to the local current density. Instead, reconnection occurs at the subsolar point via a magnetic flux pileup process, in which magnetic energy accumulates upstream of the current sheet as the IMF rotates to align itself with the X line. The dependence of the subsolar parallel electric field agrees well with the analytic resistive MHD solutions obtained by Sonnerup and Priest (J. Plasma Phys., 14, 183, 1975).
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2724 Magnetopause and boundary layers
DE: 2753 Numerical modeling
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005