Solar wind ion injections in the morning auroral oval

Energy versus time dispersion of precipitating ion bursts was observed during two rocket flights in the morning auroral oval. Individual bursts lasted about 20 seconds and repeated on a time scale of 100 seconds. The dispersion is interpreted as energy‐dependent time‐of‐flight delay which provides identification of ion charge‐to‐mass ratio as well as injection source distance. The data are consistent with injections of magnetosheath ions with injection distances ranging from 7 to 19 earth radii. Individual events extended over a region of at least several degrees of magnetic longitude and 0.3 degrees of invariant latitude. It is suggested that these events are associated with turbulent plasma entry into the magnetospheric entry layer.