FREJA OBSERVATIONS OF NARROW INVERTED-V ELECTRON-PRECIPITATION BY THE 2-DIMENSIONAL ELECTRON SPECTROMETER

Observations of several steady, approximately 1-5 km scale inverted-V's by the Freja F7 Two-dimensional Electron Spectrometer (TESP) are described. Such narrow structures are not common, but provide an opportunity for observing edge precipitation and the movement of arcs through the plasma. Velocities of inverted-V potential structures in the plasma frame can be derived from the observed time delay between precipitating and mirrored electrons. These velocities determine whether horizontal plasma flow into a potential structure can provide the source population for arc edge precipitation. It is found that the intensity of the arc edge precipitation is not associated in any expected way with this velocity, indicating another source of plasma for arc edge precipitation is required.