Electric fields and convection velocities associated with flux transfer events

Abstract

The electric field and E × B/B² velocities associated with 23 flux transfer events in the magnetosheath and magnetosphere have been examined using data from the University of California, Berkeley double probe experiment on ISEE 1. Twelve‐second averaged electric field data show perturbations in the component of the electric field perpendicular to the magnetopause with an average magnitude of 3.5 mV/m associated with the FTE's. Direct flux transfer events (those with an outward perturbation in B followed by an inward one) were found to have a northward component of the E × B velocity, while reverse flux transfer events were found to have a southward E × B velocity component, in agreement with the current FTE model. The flux tubes moved across the magnetopause plane at an average E × B speed of 125 km/s with respect to the ambient E × B flow, with events located on the dawn (dusk) side tending to move dawnward (duskward). Study of higher time resolution electric field data showed no large spiky electric fields of the type observed elsewhere in the magnetosphere (bow shock, plasmasheet boundary). Examination of the three electric field filters during FTE's showed average enhancements in the power at frequencies between 3 and 250 Hz by factors of 4–20, with maximum enhancements by two orders of magnitude.