Survey of flux transfer events observed with the ISEE 1 spacecraft: Dependence on the interplanetary magnetic field

We have surveyed the interplanetary magnetic field (IMF) dependence of isolated 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. The majority of subsolar FTEs are associated with southward IMF, consistent with previous studies. The ratio of the number of FTEs during spiral IMF orientation to that during ortho-spiral IMF is roughly the same at any MLT, an unfavorable finding for the foreshock being the source of our FTEs. The curvature force controlled by IMF B_y tends to affect significantly the motion of FTEs near noon, causing sunward moving FTEs. This behavior is consistent with reconnection being the source of our events. The totality of these results suggest that the foreshock is not the source of FTEs on the dayside magnetopause but that reconnection at the magnetopause is the source.