Solar wind excitation of Pc5 fluctuations in the magnetosphere and on the ground

The primary purpose of this paper is to show the strong link between solar wind compressional fluctuations in the 1-8 mHz frequency range and Pc5 fluctuations in the magnetosphere near the magnetopause, at geosynchronous orbit, over the poles, and on the ground. We show events in March and April 2002 using the S3C Great Observatory: specifically, ACE and Wind in the solar wind, Geotail near the magnetopause, GOES 8 and 10 at geosynchronous orbit and Cluster over the poles. Near the leading edge of high speed streams where dynamic pressure fluctuations increase dramatically, the magnetosphere responds with increased compressional fluctuations. Using four examples we show that these magnetospheric compressional fluctuations exist regardless of IMF orientation and for a wide range of speeds and dynamic pressures; the amplitude of fluctuations depends primarily on the amplitude of solar wind dynamic pressure fluctuations. Magnetospheric fluctuations are also seen during quiet solar wind conditions; there are always solar wind dynamic pressure fluctuations of some amplitude. The compressional fluctuations are strongest on the ground near footpoints of magnetic field lines attached to the magnetopause. Enhanced fluctuation levels are also seen at ground stations near footpoints of geostationary orbiting satellites. Ground fluctuations are stronger than magnetospheric fluctuations. Solar wind driven compressional fluctuations are stronger on the dayside compared with the flanks or magnetotail. This may be explained by the direction of the Poynting Flux at the magnetopause determined using Geotail data. The Poynting Flux is primarily directed inward (and outward due to the oscillating nature of the waves) so that more flux is focused on the dayside.