Articles | Volume 27, issue 2
Ann. Geophys., 27, 725–743, 2009
Ann. Geophys., 27, 725–743, 2009

  16 Feb 2009

16 Feb 2009

Cluster and Double Star multipoint observations of a plasma bubble

A. P. Walsh1, A. N. Fazakerley1, A. D. Lahiff1, M. Volwerk2, A. Grocott3, M. W. Dunlop4, A. T. Y. Lui5, L. M. Kistler6, M. Lester3, C. Mouikis6, Z. Pu7, C. Shen8, J. Shi8, M. G. G. T. Taylor9, E. Lucek10, T. L. Zhang2, and I. Dandouras11 A. P. Walsh et al.
  • 1Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
  • 2Space Research Institute, Austrian Academy of Sciences, Schmiedlstra{ß}e 6, 8042 Graz, Austria
  • 3Department of Physics and Astronomy, University of Leicester, University Rd, Leicester, LE1 7RH, UK
  • 4Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon, OX11 0QX, UK
  • 5The Johns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel MD, 20723-6099, USA
  • 6Department of Physics, University of New Hampshire, Durham NH, 03824, USA
  • 7Peking University, Beijing, China
  • 8State Key Laboratory for Space Weather, CSSAR, Chinese Academy of Sciences, Beijing 100080, China
  • 9European Space Technology Centre, Keplerlaan 1, Po Box 299, 2200 AG Noordwijk, The Netherlands
  • 10Blackett Laboratory, Imperial College, London, UK
  • 11Centre d'Etude Spatiale des Rayonnements, Toulouse, France

Abstract. Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005, during a period of southward, but BY-dominated IMF. In particular the first direct observations of return flows around the edges of a plasma bubble, and the first observations of plasma bubble features within 8 RE of the Earth, consistent with MHD simulations (Birn et al., 2004) are presented. The implications of the presence of a strong BY in the IMF and magnetotail on the propagation of the plasma bubble and development of the associated current systems in the magnetotail and ionosphere are discussed. It is suggested that a strong BY can rotate the field aligned current systems at the edges of the plasma bubble away from its duskward and dawnward flanks.