SHORT-DURATION CONVECTION BAYS AND LOCALIZED INTERPLANETARY MAGNETIC-FIELD STRUCTURES ON NOVEMBER 28, 1995

We present ground-based, plasma sheet, and magnetosheath observations of two subsequent short-duration (10-20 min) increases of the postmidn ight westward electrojet on November 28, 1995. Appearing: as though sm all (150-200 nT) substorms, they were not accompanied by any substorm expansion onset signatures. Auroral breakup, worldwide Pi2 pulsations, and the corresponding plasma sheet activity, such as fast flows, curr ent disruption, and plasmoid generation, were all observed only at the recovery of the second electrojet increase. These convection bays wer e associated with the equatorward expansion of the auroras and simulta neous magnetic variations in the polar cap and middle latitudes. Growt h phase signatures of the lobe field increase and tailward stretching of magnetic field were also observed in the plasma sheet. Bursty bulk flows in the plasma sheet seem to be quenched at the onset of first co nvection bay and did not resume until the auroral breakup which conclu ded the second convection bay, A point of interest of this event was t he ''incomplete'' convection/current system with a well-developed dawn vortex in the absence of well-defined dusk vortex; instead, a complic ated transient activity dominated over the afternoon-dusk local time s ector. We interpret this asymmetry either in terms of the magnetopause encounter with the edge of the solar wind driver, i.e., strong southw ard IMF, which hits only the dawn part of the magnetosphere, or with a n extremely slant interplanetary discontinuity. This unique configurat ion was inferred from observations of uncorrelated strong southward B- z events by the Wind and IMP 8 spacecraft in the dusk and dawn magneto sheath, respectively, as well as from the directional analysis of the interplanetary discontinuities which form the edges of these structure s, We suggest that interaction of the magnetosphere with very slant so lar wind discontinuities may bring various specific features to magnet ospheric and ionospheric dynamics that have not been reported.