Survey of flux transfer events observed with the ISEE 1 spacecraft: Rotational polarity and the source region

We have surveyed transient bipolar perturbations of the magnetic field component normal to the magnetopause, identifiable as flux transfer events (FTEs), from nine seasons during which the ISEE 1 spacecraft completely precessed through the dayside magnetosheath and magnetosphere. Our results indicate that FTEs tend to occur more frequently at postnoon local times, rather than the expected prenoon local times if these events had been associated with pressure pulses generated in the foreshock. The amplitude of both the magnetosheath FTEs and the magnetospheric FTEs tends to decrease, whereas the duration of the FTEs tends to increase, with increasing distance from the magnetopause. The occurrence rate of FTEs tends to increase with decreasing distance from the magnetopause. These features strongly indicate a magnetopause origin for FTEs in both regions. The rotational polarity of the magnetic field perturbations in a plane roughly parallel to the equator reverses across the noon meridian and across the magnetopause. This feature is consistent with an interpretation in which FTEs are generated on the dayside magnetopause and subsequently move antisunward along the magnetopause.