DAYSIDE AURORAL CONFIGURATIONS - RESPONSES TO SOUTHWARD AND NORTHWARDROTATIONS OF THE INTERPLANETARY MAGNETIC-FIELD

We report specific types of daytime auroral activities occurring in re sponse to certain rotations of the interplanetary magnetic field (IMF) . The IMF rotations we focus on consist of a sharp southward turning f rom an initial northward orientation, followed by slower rotations bac k to an intermediate state, which is dominated by the B-y component (s mall B-z). When the IMF turned from north to south, the dayside aurora l configuration changed from one typical of northward conditions to on e typical of southward conditions. The type 2 cusp aurora in the north (similar to 78 degrees-79 degrees magnetic latitude) was replaced by activation of a sequence of moving auroral forms (type 1 cusp aurora) at lower latitudes, each form appearing at the equatorward boundary of the previous one, resulting in similar to 100-to 200-km total displac ements of the auroral equatorward boundary in the cusp region during i ntervals of similar to 5- to 10-min duration. This auroral activity is accompanied by enhancement of ionospheric convection and onset of mag netic bays on the ground. Since southward rotations of the IMF are exp ected to give rise to enhancements of the magnetopause reconnection ra te, we conclude that these auroral/convection events represent distinc t ionospheric signatures of such reconnection rate enhancements. When the, IMF turned partially northward again, into an intermediate state, the aurora responded as expected, i.e., the equatorward auroral displ acement was halted or reversed, and the type 2 aurora reappeared. The coexistence of the types 1 and 2 cusp auroras in the intermediate stat e is interpreted in terms of the simultaneous occurrence of reconnecti ons at low and high magnetopause latitudes. The dynamical configuratio ns of particle precipitation and ionospheric convection in the cusp re gion in such cases are discussed.