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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 6
Ann. Geophys., 15, 671–684, 1997
https://doi.org/10.1007/s00585-997-0671-4
© European Geosciences Union 1997
Ann. Geophys., 15, 671–684, 1997
https://doi.org/10.1007/s00585-997-0671-4
© European Geosciences Union 1997

  30 Jun 1997

30 Jun 1997

The response of the magnetosphere to the passage of a coronal mass ejection on March 20−21 1990

J. R. Taylor1, M. Lester1, T. K. Yeoman1, B. A. Emery2, D. J. Knipp3, D. Orr4, S. I. Solovyev5, T. J. Hughes6, and H. Lühr7 J. R. Taylor et al.
  • 1Department of Physics and Astronomy, University of Leicester, University Road, Leicester UK
  • 2High Altitude observatory, NCAR, POB 3000, Boulder, Colorado, USA
  • 3Department of Physics, US Airforce Academy, Colorado, USA
  • 4Department of Physics, University of York, York, UK
  • 5Institute of Cosmophysical Research and Aeronomy, 31 Lenin Avenue., 677891, Yakutsk, Russia
  • 6Herzberg Institute of Astrophysics, National Research Council of Canada, Ottawa, Ontario, Canada
  • 7Institut für Geophysik und Meteorologie, Technische Universität, Braunschweig, D-38106 Braunschweig, Germany

Abstract. The geomagnetic response to the passage of a coronal mass ejection (CME) is studied. The passage of the CME resulted in a storm sudden commencement (SSC) at 2243 UT on March 20 1990 with disturbed magnetic activity during the following 24 h. The auroral, sub-auroral and equatorial magnetic response to the southward turning at 1314 (±5) UT on March 21 and the equatorial response to the southward turning associated with the SSC on 20 March are discussed in terms of existing models. It is found that the auroral and sub-auroral response to the southward turning associated with the SSC is a factor 2 or more quicker than normal due to the shock in the solar wind dynamic pressure. The low-latitude response time to the southward turning, characterised by Dst and the magnetopause current corrected Dst*, is unaffected by the shock. Dst and Dst*, characteristic of the equatorial magnetic field, responded to the 1314 (±5) UT southward turning prior to the first observed substorm expansion phase onset, suggesting that a dayside loading process was responsible for the initial enhancement in the ring current rather than nightside particle injection. The response time of the auroral and sub-auroral magnetic field to the southward turning at 1314 (±5) UT on March 21 is measured at a variety of longitudes and latitudes. The azimuthal propagation velocity of the response to the southward turning varied considerably with latitude, ranging from ~8 km s–1 at 67°N to ~4 km s–1 at 55°N. The southward velocity of the equatorward boundary of the northern polar convection pattern has been measured. This velocity was ~1.2 km s–1 at 1600 MLT, although there was evidence that this may vary at different local times.

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