Westward traveling surge dynamics and the local structure of an isolated substorm Original Research Article

We present a case study of a simple isolated substorm. We compare magnetic field and optical observations at Kola Peninsula with POLAR UVI, POLAR/PIXIE and LANL satellite data to examine the relationshipships between global and local auroral structures and their dynamics. In addition to the active phase of the substorm with a main onset, there are two additional Westward Traveling Surge (WTS) intensifications accompanied by energetic particle acceleration and magnetic field dipolarization in associated local sectors of the magnetosphere. The longitudinal dimensions of the main auroral bulge and the WTS were restricted and in neighboring sectors quite different types of activity were observed. The effects of the fragmentation of the night side auroral magnetosphere into sectors with simultaneous auroral bulge expansion and local growth phase may help explain the temporal structure of multiple-onset substorms. Related problems of the substorm geometry are briefly discussed.