Interball and Geotail Observations of Flux Transfer Events

Abstract

We present preliminary results from case and statistical studies of flux trans-fer events (FTEs) observed by the Geotail and Interball spacecraft on the dayside and flank magnetopause. At 1530 universal time (UT) on January 29, 1996, Geotail was located just inside the prenoon magnetopause, where it observed a series of transient events marked by bipolar flow signatures normal to the nominal magnetopause. There were no significant magnetic field signatures normal to the magnetopause. We interpret the observations as evidence indicating that the events were nearly aligned with the northward magnetospheric magnetic field. On October 18, 1995, Interball-1 was located outside the northern flank magnetopause, where it observed a series of northward-moving magnetosheath FTEs marked by bursts of energetic particles, depressed plasma densities, and bipolar magnetic field signatures normal to the nominal magnetopause during a period of strongly northward interplanetary magnetic field orientation. IMP-8, located near the other flank magnetopause did not observe any F1’Es. Geotail served as a solar wind monitor but observed no significant solar wind pressure variations. Finally, we present initial statistical results from a survey of several hundred dayside Fibs observed by Geotail. The events show a marked tendency to occur for southward magnetosheath magnetic field orientations. We present statistics concerning their amplitudes and direction of motion.