Flux transfer events: Scale size and interior structure

We report the first direct investigation of the spatial properties of flux transfer events (FTEs) at the Earth's dayside magnetopause. Simultaneous magnetometer and plasma data from the ISEE 1 and 2 satellites are combined to show that magnetosheath FTEs can have a scale size of order an Earth radius in the magnetopause normal direction. We confirm that the magnetic field within the events appears to be twisted, this twisting corresponding to a core field‐aligned current of magnitude a few × 105 A. We also show evidence for plasma vorticity in FTEs. The transverse flow and field perturbations accompanying the three events studied obey approximately the Walén relation for a propagating Alfvén wave