GLOBAL ANALYSIS OF 3 TRAVELING VORTEX EVENTS DURING THE NOVEMBER 1993STORM USING THE ASSIMILATIVE MAPPING OF IONOSPHERIC ELECTRODYNAMICS TECHNIQUE

We have studied three traveling vortex events during the November 3-11 , 1993, storm period using the assimilative mapping of ionospheric ele ctrodynamics technique to help interpret the ground magnetic response from a global set of stations. When the AMIE potential patterns are hi gh-pass filtered, clear vortex structures are observed. The AMIE outpu t compares reasonably well with the ground magnetic data, although AMI E has a tendency to smooth out the structures. Single vortices are obs erved to form near 1000 MLT and propagate to 1400 MLT, over the Greenl and magnetometers and across noon. The velocity of the vortices is app roximately 4-8 km/s (0.2 degrees - 0.3 degrees s(-1) between 70 degree s and 75 degrees) eastward along a line of invariant latitude. The num ber of vortices, as well as the motion of the vortices, differs from t he classical picture of a traveling convection vortex. We therefore su ggest that these vortex events might have a different generation mecha nism or occur under a different state of the magnetosphere, and thus t hat they should be considered a separate class of events. The AMIE tec hnique offers the possibility to relate the vortices to the large-scal e convection patterns. We note how the vortices can be interpreted as small scale, rapid changes in the large-scale convection pattern, alth ough these changes show many differences to previous studies of changi ng large-scale convection patterns. We speculate that this particular class of traveling vortex event may be generated by a perturbation in the separatric on the dayside magnetopause, caused by an enhancement o r depreciation of the magnetic merging.