Auroral and Geomagnetic Signatures of Flux Transfer Events and Associated Current Systems for Positive and Negative IMF BY

We interpret certain characteristic sequences of ionospheric poleward moving events near the cusp, seen simultaneously in dayside aurora and ground magnetometer observations, as flux transfer event (FTE) signatures and propose associated FTE current systems. This current system consists of a central filament or sheet-like field-aligned current, located on newly opened field lines with oppositely directed return currents on the poleward and equatorward sides. The propagation speed is found to be 1–2 km/s, and the size of the current system 2–300 km in the north-south direction. The FTE current system has opposite polarities corresponding to positive and negative IMF B y component. The events are typically observed in the prenoon sector for positive B y and postnoon during negative B y conditions. In this study we present two case examples, one of each category.