Analysis of ATS-5 particle spectrograms and simultaneous meridian-scanning photometer data (keograms) obtained at the base of the ATS field line has revealed systematic relationships between temporal and spatial auroral morphology and particle injection events. The details of these relationships depend on previous injection events, and the extent and magnitude of current injections.

A persistent zone of weak aurora is related to steady plasma-sheet drizzle, and the equatorward edge of this aurora delineates field lines threading the inner edge of the plasma sheet. Auroras associated with injection events superimpose on this pre-existing pattern, with the lowest latitude of new precipitation (the injection boundary) depending on local time.

In general, plasma energization is not required between the equatorial plane and the ionosphere to account for observed auroral intensities, although there are examples when such energization probably occurs. The data also indicate occasional occurrence of enhanced loss-cone fluxes, suggesting low-latitude field-aligned acceleration.

A summary figure shows how various characteristic auroral precipitation regions are related to the shape, extent and orientation of the substorm injection boundary, and to subsequent drift paths of injected plasma.