Observed Tail Current Systems Associated with Bursty Bulk Flows and Auroral Streamers During a Period of Multiple Substorms

We present a multi-instrument study of a substorm bursty bulk flow (BBF) and auroral streamer. During a substorm on the 25 August 2003, which was one of a series of substorms that occurred between 00:00 and 05:00~UT, the Cluster spacecraft encountered a BBF event travelling Earthwards and duskwards with a velocity of ~500~{km~s-1} some nine minutes after the onset of the substorm. Coincident with this event the IMAGE spacecraft detected an auroral streamer in the substorm auroral bulge in the southern hemisphere near the footpoints of the Cluster spacecraft. Using FluxGate Magnetometer (FGM) data from the four Cluster spacecraft, we determine the field-aligned currents in the BBF, using the curlometer technique, to have been ~5~{mA~km-2}. When projected into the ionosphere, these currents give ionospheric field-aligned currents of ~ 18~{A~km-2}, which is comparable with previously observed ionospheric field-aligned current associated with BBFs and auroral streamers. The observations of the BBF are consistent with the plasma "bubble" model of Chen and Wolf (1993) and with the reconnection of open field-lines Earthward of the substorm associated near-Earth neutral line for the creation of BBFs.