A review of riometer data from the south pole (74.2¿ invariant latitude) for a 7-year period (1967--1973) indicates the occurrence of sc-triggered poleward expansions of auroral absorption regions. For 15 such events the average AE index in the hour before the sc's was twice as large as that for 30 sc's that did not trigger substorm events at auroral latitudes. This result indicates that the triggering of substorms involves the enhancement of processes already in progress by the compression of the magnetosphere.