HR: 08:35h
AN: SM11C-03    [Abstracts]
TI: A Theory of Solar-Wind/Magnetosphere Coupling Derived from First Principles
AU: * Borovsky, J
EM: jborovsky@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop d466, Los Alamos, NM 87545,
AU: Birn, J
EM: jbirn@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop d466, Los Alamos, NM 87545,
AU: Hesse, M
EM: michael.hesse@nasa.gov
AF: NASA/Goddard, CCMC, Greenbelt, MD 20771,
AB: A formula that expresses the dayside reconnection rate in terms of upstream solar wind parameters is derived and tested. The derivation is based on the principle that dayside reconnection is governed by local plasma parameters and that whatever controls those parameters controls the reconnection rate. The starting point of the derivation is the Cassak-Shay formula, which expresses the dayside reconnection rate in terms of four parameters: the magnetic-field strengths in the magnetosphere and magnetosheath and the plasma mass densities in the magnetosphere and magnetosheath. Using the Rankine-Hugoniot relations at the bow shock and an analysis of the magnetosheath flow, three of these parameters are expressed in terms of upstream-solar- wind parameters. These three expressions are then used in the Cassak-Shay formula to obtain the "solar-wind control function". The interpretation of the control function is that solar-wind pressure largely sets the reconnection rate. The solar-wind magnetic field enters into the control function because of a bow-shock Mach-number dependence. The "plasmasphere effect", wherein the magnetosphere begins to exert control over solar-wind/magnetosphere coupling, is captured by the formula. Using the OMNI2 data set and seven geomagnetic indices, the solar-wind control function is tested on its ability to describe the variance in the geomagnetic indices. The control function is found to be very successful, statistically as good as the best "solar-wind driver function" in the literature.
DE: 2784 Solar wind/magnetosphere interactions
DE: 7835 Magnetic reconnection (2723, 7526)
DE: 7924 Forecasting (2722)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting