Flux transfer events at the magnetopause and in the ionosphere

On December 1, 1986 the ISEE 1 and 2 spacecraft pair passed through the dayside magnetopause at a location which mapped approximately to ionospheric field‐line foot‐points near the fields of view of the EISCAT radar and photometers and an all‐sky camera on Svalbard. The magnetosheath magnetic field was southward and duskward at the time, and flux transfer events (FTEs) were observed at the ISEE location. At the same time, the EISCAT radar observed ionospheric flow bursts of up to 1 km s −1 . The peak of each burst followed an FTE observation at ISEE by a few minutes. The bursts, each lasting ten or fifteen minutes, were comprised of first a westward then a poleward flow. An all‐sky camera at Ny Ålesund observed dayside auroral breakup forms during or shortly after the flow bursts, moving westward then poleward. While these flow bursts and associated dayside auroral forms have been previously reported in association with southward IMF orientations, this is the first observation of a direct link to FTEs at the magnetopause. On this occasion, the lower limit on the inferred potential associated with the FTEs is roughly 10 kV. Their inferred east‐west extent in the ionosphere ranges between 700 and 1000 km, corresponding to a 3 – 5 R E local time extent at the average magnetopause.