Articles | Volume 23, issue 8
Ann. Geophys., 23, 2915–2920, 2005

Special issue: Double Star - First Results

Ann. Geophys., 23, 2915–2920, 2005

  08 Nov 2005

08 Nov 2005

Cluster and Double Star observations of dipolarization

R. Nakamura1, W. Baumjohann1, T. L. Zhang1, C. M. Carr2, A. Balogh2, K-H. Fornacon3, E. Georgescu4, H. Rème5, I. Dandouras5, T. Takada1, M. Volwerk1,4, Y. Asano1, A. Runov1, H. Eichelberger1, B. Klecker4, C. Mouikis6, L. M. Kistler6, and O. Amm7 R. Nakamura et al.
  • 1Space Research Institute, Austrian Academy of Sciences, 8042 Graz, Austria
  • 2Space and Atmospheric Phys. Group, Blackett Lab., Imperial College, London SW72BZ, UK
  • 3Inst. für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, 38 106 Braunschweig, Germany
  • 4Max-Planck Inst. für extraterrestrische Physik, 85 748 Garching, Germany
  • 5Centre d’Etude Spatiale des Rayonnements, 31 028 Toulouse, Cedex 4, France
  • 6Space Science Center, Science and Engineering Research Center, University of New Hampshire, Durham, NH 03824, USA
  • 7Finnish Meteorological Institute, Space Research, 00 101 Helsinki, Finland

Abstract. We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but this was not the case for TC-1. For both events the satellites crossed near the conjugate location of the MIRACLE stations. By using multi-point analysis techniques, the direction/speed of the propagation is determined using Cluster and is then compared with the disturbances at TC-1 to discuss its spatial/temporal scale. The propagation direction of the BZ disturbance at Cluster was mainly dawnward with a tailward component for 7 August and with a significant Earthward component for 14 August associated with fast flows. We suggest that the role of the midtail fast flows can be quite different in the dissipation process depending on the condition of the IMF and resultant configuration of the tail.