Which magnetic storms produce relativistic electrons at geosynchronous orbit?

Relativistic electrons appear in the geosynchronous environment following s ome, but not all, geomagnetic storms. The ability to identify which storms produce these electrons would bring us much closer to explaining the mechan ism responsible for their appearance, and it would provide the space weathe r community with a means to anticipate the electron hazard to geosynchronou s spacecraft. We apply a recently developed statistical technique to produc e an hourly time series of relativistic electron conditions at local noon a long geosynchronous orbit using several geosynchronous monitors. We use a c ross-correlation analysts to determine what parameters in the solar wind an d magnetosphere might influence the Aux of relativistic electrons. We then perform a superposed epoch analysis to compare storms with and storms witho ut the appearance of these electrons. We investigate a number of solar wind and magnetospheric parameters for these two sets of storms at 1-hour resol ution, In particular, sustained solar wind velocity in excess of 450 km s(- 1) is a strong external indicator of the subsequent appearance of relativis tic electrons, :ln the magnetosphere, long-duration elevated Pc 5 ULF wave power during the recovery phase of magnetic storms appears to discriminate best between those storms that do and do not produce relativistic electrons .