Cluster and Double Star observations of dipolarization

R. Nakamura (1) , W. Baumjohann (1) , T. L. Zhang (1) , Chris M. Carr (2) , A. Balogh (2) , K.-H. Fornacon (3) , E. Georgescu (4) , H. Rème (5) , I. Dandouras (5) , T. Takada (1) , M. Volwerk (1, 4) , Y. Asano (1) , A. Runov (1) , H. Eichelberger (1) , B. Klecker (4) , C. Mouikis (6) , L. M. Kistler (6) , O. Amm (7)

1 IWF - Space Research Institute of Austrian Academy of Sciences
2 Space and Atmospheric Physics Group [London]
3 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
4 MPE - Max-Planck-Institut für Extraterrestrische Physik
5 CESR - Centre d'étude spatiale des rayonnements
6 SSC - UNH Space Science Center [Durham]
7 FMI - Finnish Meteorological Institute

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 B_Z 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

R. Nakamura, W. Baumjohann, T. L. Zhang, Chris M. Carr, A. Balogh, et al.. Cluster and Double Star observations of dipolarization. Annales Geophysicae, 2005, 23 (8), pp.2915-2920. ⟨hal-00330040⟩