Global analysis of three traveling vortex events during the November 1993 storm using the assimilative mapping of ionospheric electrodynamics technique

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Abstract
We have studied three traveling vortex events during the November 3–11, 1993, storm period using the assimilative mapping of ionospheric electrodynamics technique to help interpret the ground magnetic response from a global set of stations. When the AMIE potential patterns are high‐pass filtered, clear vortex structures are observed. The AMIE output compares reasonably well with the ground magnetic data, although AMIE has a tendency to smooth out the structures. Single vortices are observed to form near 1000 MLT and propagate to 1400 MLT, over the Greenland magnetometers and across noon. The velocity of the vortices is approximately 4–8 km/s (0.2° – 0.3° s−1 between 70° and 75°) eastward along a line of invariant latitude. The number of vortices, as well as the motion of the vortices, differs from the classical picture of a traveling convection vortex. We therefore suggest that these vortex events might have a different generation mechanism or occur under a different state of the magnetosphere, and thus that they should be considered a separate class of events. The AMIE technique offers the possibility to relate the vortices to the large‐scale convection patterns. We note how the vortices can be interpreted as small scale, rapid changes in the large‐scale convection pattern, although these changes show many differences to previous studies of changing 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 or depreciation of the magnetic merging.

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