Dynamics of the Inner Magnetosphere Eestimated From Geosynchronous Observation

We have examined the characteristics of magnetic field variations at geosynchronous orbit using magnetic field data from GOES satellites located at different geomagnetic latitudes and solar wind data from Wind and ACE satellites for the period from 1996 to 1999. We binned the data on the magnetic field data for every 5 degrees range of the dipole tilt angle, since the trend of magnetic field variations at geosynchronous orbit changes depending on the dipole tilt angle. The results of our data analysis suggests that the magnetic field variations at geosynchronous orbit strongly depend on the variations of dynamic presure of solar wind and those of pressure corrected Dst index (Dst*). The dependence of solar wind electric field is not significant rather than the dependence of Dst*. And magnetic field variations at dayside has a weak dependence of dipole tilt angle on VDH coordinate system but those at nightside has a strong dependence. This difference corresponds to the origin and location of the current system in the inner magnetosphere. However, the Dst* dependences of magnetic field variations derived from two different magnetic latidudes suggest that these magnetic field variations can be explained by the existence of equivalent westward current beyond the geosynchronous orbit. This suggests that westward current grobally dominates in the inner magnetosphere during storm time.