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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 25, issue 4
Ann. Geophys., 25, 1001-1009, 2007
https://doi.org/10.5194/angeo-25-1001-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 1001-1009, 2007
https://doi.org/10.5194/angeo-25-1001-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  08 May 2007

08 May 2007

Prelude to THEMIS tail conjunction study

A. T. Y. Lui1, Y. Zheng1, Y. Zhang1, V. Angelopoulos2, G. K. Parks2, F. S. Mozer2, H. Rème3, L. M. Kistler4, M. W. Dunlop5, G. Gustafsson6, and M. G. Henderson7 A. T. Y. Lui et al.
  • 1JHU/APL, Laurel, MD 20723-6099, USA
  • 2Space Sciences Laboratory, UCB, Berkeley, CA, USA
  • 3CESR, BP4346, 31028 Toulouse Cedex 4, Toulouse, France
  • 4University of New Hampshire, Durham, NH, USA
  • 5Space Science and Technology Department, RAL, Chilton, Didcot, Oxfordshire OX11 0QX, UK
  • 6Swedish Institute of Space Physics, Uppsala Division, 755 91 Uppsala, Sweden
  • 7LANL, MS D466, Los Alamos, NM, USA

Abstract. A close conjunction of several satellites (LANL, GOES, Polar, Geotail, and Cluster) distributed from the geostationary altitude to about 16 RE downstream in the tail occurred during substorm activity as indicated by global auroral imaging and ground-based magnetometer data. This constellation of satellites resembles what is planned for the THEMIS (Time History of Events and Macroscopic Interactions during Substorms) mission to resolve the substorm controversy on the location of the substorm expansion onset region. In this article, we show in detail the dipolarization and dynamic changes seen by these satellites associated with two onsets of substorm intensification activity. In particular, we find that dipolarization at ~16 RE downstream in the tail can occur with dawnward electric field and without plasma flow, just like some near-Earth dipolarization events reported previously. The spreading of substorm disturbances in the tail coupled with complementary ground observations indicates that the observed time sequence on the onsets of substorm disturbances favors initiation in the near-Earth region for this THEMIS-like conjunction.

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