Development of the Auroral Substorm in the Framework of the Double Oval

TL;DRAbstract

The original substorm development was portrayed as the appearance and subsequent development of discrete auroral arcs, forming an auroral bulge in the midnight sector extending into the evening hours. As early as the 1970’s, it became clear that the auroral oval had a finite latitudinal width, and that auroral activations tended to occur in two distinct zones, viz. the poleward and equatorward edges of the oval. This large scale structure which is most evident in the evening and midnight sectors has been termed the double oval, and there is good reason to believe that the development of the auroral substorm must be discussed in the framework of the double oval. It is generally accepted that the onset of the substorm expansion phase occurs on the equatorward branch of the double oval, and that the latter stages of the expansion phase feature significant auroral activations on the poleward branch. In this paper, the significance of poleward boundary intensifications (PBIs) as they pertai

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