Field Line Dependence of Mass Density at Geosynchronous Orbit

Using 12 years (1980-1991) of measurements of Alfven wave frequencies by the GOES spacecraft at geosynchronous orbit, we examine the ratios of frequency harmonics in order to determine the field line dependence of mass density. Parameters on which these frequency ratios depend include magnetic local time MLT, the solar radiation as described by the ultraviolet solar index F10.7, the geomagnetic activity as specified by the Kp index, and the wave amplitude. Results to date will be presented.