HR: 16:15h
AN: SM54A-02    [Abstracts]
TI: Estimates of the influence of solar wind drivers on the semiannual variation in geomagnetic activity
AU: * Weigel, R S
EM: Robert.Weigel@lasp.colorado.edu
AB: A common explanation for the semiannual variation in geomagnetic activity is that it results from a semiannual variation in the strength of solar wind drivers of geomagnetic activity. Using epoch analysis and impulse response functions, we estimate the influence of various solar wind drivers of activity, including variations in reconnection amplitude, reconnection efficiency, and solar wind density variations. The data set analyzed includes the am, ap, and AE indices along with at least a full solar cycle of hourly measurements from 4 ground magnetometer stations. Using these methods we find that the solar wind influence is generally less than 20% of the total semiannual variation and this influence depends on geomagnetic latitude. The results of this analysis are used to develop constraints on a theory of the semiannual variation that cannot be explained by changes in solar wind driving.
DE: 2407 Auroral ionosphere (2704)
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005