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Ann. Geophys., 23, 2915-2920, 2005
www.ann-geophys.net/23/2915/2005/
© European Geosciences Union 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
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.
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