Observed tail current systems associated with bursty bulk flows and auroral streamers during a period of multiple substorms
1Dept. Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
2CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346, 31028, Toulouse Cedex 4, France
3Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
4Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
5National Institute of Polar Research, 9-10-1 Kaga, Itabashi, Tokyo 173-8515, Japan
6Blackett Laboratory, Imperial College, London, SW7 2BZ, UK
7Atmosphere Space Research Division, Danish Meteorological Institute, Copenhagen, Denmark
Abstract. We present a multi-instrument study of a substorm bursty bulk flow (BBF) and auroral streamer. During a substorm on 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 currents associated with BBFs and auroral streamers. The observations of the BBF are consistent with the plasma "bubble" model of Chen and Wolf (1993). Furthermore, we show that the observations of the BBF are consistent with the creation of the BBF by the reconnection of open field lines Earthward of a substorm associated near-Earth neutral line.
Citation: Forsyth, C., Lester, M., Cowley, S. W. H., Dandouras, I., Fazakerley, A. N., Fear, R. C., Frey, H. U., Grocott, A., Kadokura, A., Lucek, E., Rème, H., Milan, S. E., and Watermann, J.: Observed tail current systems associated with bursty bulk flows and auroral streamers during a period of multiple substorms, Ann. Geophys., 26, 167-184, doi:10.5194/angeo-26-167-2008, 2008.