Influence on AE index of substorms appearing north of Cambridge Bay

An analysis of Canadian data for the interval 1972-1978 suggests that the AE index may be in error at times by 150 nT or more. It is shown that the AE index could be improved (1) by including stations at the northern boundary of the auroral oval, such as Cambridge Bay, in the AE network of observatories and (2) by using an interval of digitization less than 2.5 min and preferably equal to 1 min (as has been the case since January 1976), as large peaks occurring at intervals less than 2.5 min have been lost in the scaling procedure.