Wednesday

We present a detailed case study of high-latitude aurora observed in the dayside northern hemisphere polar cap, under particularly strong and sustained northward interplanetary field conditions, perhaps associated with an interplanetary magnetic cloud. The entire magnetopause is likely to be compressed, even under these northward conditions. The aurora are accompanied by well-defined NBZ currents, that dominate the nominal R1-R2 field-aligned current system. We track the evolution of the cusp spot, observing aurora resulting from both electron and proton precipitation, over a 12 hour period, as these emissions respond quickly to changes in the By component of the interplanetary magnetic field. Fast sunward flows are observed that often align with the eastern side of the cusp spot emission. This cusp spot occurs immediately prior to an occurrence of region 2 currents that bifurcate on the dusk side, and that appear to be associated with substorms.