SOLAR-WIND PROPERTIES OBSERVED DURING HIGH-LATITUDE IMPULSIVE PERTURBATION EVENTS

The data base from the 1985–86 Balloon Campaign at South Pole Station, Antarctica, has been searched for impulsive magnetic and electric field events that occurred when IMP 8 was in the solar wind and data were acquired. Two events are shown that appear to be similar to published examples of high latitude “twin vortex” current systems. Neither event was preceded by a dynamic pressure pulse in the solar wind. These examples disprove the hypothesis that all such high‐latitude impulses arise solely from dynamic pressure pulses produced by the solar wind. Further, on a statistical basis, a total of 42 events were found for which IMP 8 data are available. Of these events, 12 occurred when the ZGSM component (BZ) of the interplanetary magnetic field (IMF) was northward and 30 occurred when BZ was southward. Only 3 of the BZ north cases and only 5 of the BZ south cases were preceded by pressure pulses greater than 0.4 nPa in amplitude. Copyright 1990 by the American Geophysical Union.