HR: 1340h
AN: SM43A-1138    [Abstracts]
TI: Impulse Response of the Polar Cap Index ({\it PC}) to Interplanetary Coupling Using a Revised Weimer Solar Wind Propagation Method
AU: * Bargatze, L F
EM: lfb@coast.ucsd.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90095-1567 United States
AU: McPherron, R L
EM: rmcpherron@igpp.ucla.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90095-1567 United States
AU: McPherron, R L
EM: rmcpherron@igpp.ucla.edu
AF: Department of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567 United States
AB: Currently, the methods used to model solar wind propagation delay from an upstream monitor to the subsolar bow shock are receiving a great deal of renewed interest. A new generation of delay correction techniques, such as that presented by {\it Weimer et al.} [2003], have been proposed to correct for timing differences between the arrivals of IMF features at the fleet of monitoring satellites situated in the interplanetary medium upstream of the Earth. The new techniques, which rely on the use of ``phase plane'' whose tilts vary continuously with time, can be used to match the IMF time series observed at different upstream monitors with a high degree of accuracy. This recent advance motivates a reassessment of our ability to model the solar wind impulse response of geomagnetic activity indices such as the {\it PC} index, which is based on horizontal magnetic field deviations from quiet levels as observed at a ground station located near either the northern or southern magnetic pole. With this goal in mind, results will be presented characterizing the effect of the choice of propagation delay technique on the empirical response of {\it PC} to solar wind-magnetosphere coupling. Preliminary results utilizing data from July 1999 indicate that the modeling efficiency, as measured using the ratio of the modeled variance to the original variance for the {\it PC} index time series, shows a modest increase from 47% to 48.5% when using the revised Weimer propagation delay technique in place of older techniques ({\it i.e.} the ballistic {\it X/V}, corotation, or "half-way" methods) that are based on fixed phase plane tilts. The small 1.5% increase in modeling efficiency obtained for the July 1999 data set is still at least an order of magnitude larger than the differences in modeling efficiencies obtained using the various older propagation delay techniques. Effects of the choice of propagation delay model on the temporal details of the {\it PC} index impulse response filter specifically related to causality and bimodal character will also be addressed.
DE: 2134 Interplanetary magnetic fields
DE: 2409 Current systems (2708)
DE: 2776 Polar cap phenomena
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting