Examples of data from DE-2 satellite instruments are presented. These illustrate the behaviour of plasma parameters in the F-region and adjacent topside ionosphere during rapid sub-auroral ion drift (SAID) events. In particular, a variety of behaviours of the electron temperature e is demonstrated, both within and equatorward of the SAID region. The Sheeld University plasmasphere-ionosphere model (SUPIM) is used to perform calculations in which a model SAID is applied to a plasma¯ux tube. The

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... del results indicate that strongly elevated ion temperature (a recognised signature of SAID events) is on occasion sucient to raise e to observed values by ion-electron heat transfer. On other occasions, an additional heat source is required. It is suggested that such a source for the electron gas may be due to interaction between the ring current and the plasmasphere at high altitudes. The magnitude of the downward heat¯ux is consistent with that necessary to produce sub-auroral red arcs. The resulting strongly heated electron gas causes vibrational excitation of molecular nitrogen in the thermosphere.