Mathematics – Logic
Scientific paper
Jun 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997angeo..15..671t&link_type=abstract
Annales Geophysicae, vol. 15, Issue 6, pp.671-684
Mathematics
Logic
2
Scientific paper
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. Acknowledgements. We would like to thank the world-wide providers of ground magnetometer data, both for the stations shown explicitly in this study, and for stations that provided estimates of the AMIE-derived convection patterns, AL index, and Dst index. The AMIE convection patterns also owe thanks to DMSP satellite measurements of elctron precipitation and ion drift, as well as measurements from digisondes, HF radars, and incoherent scatter radars. Some of these data were taken from the CEDAR Data base, which is supported by the National Science Foundation. The Greenland magnetometer data were provided by E. Friis-Christensen, Danish Meteorological Institute. The CANOPUS instrument array was constructed and is maintained and operated by the Canadian Space Agency for the Canadian scientific community. We would also like to thank Dr. E.P. Karin of WDC-B2 in Moscow for invaluable analogue Russian magnetometer plots. We thank the IMP-8 magnetometer team at the Laboratory for Extraterrestrial Physics/GSFC for providing the IMF data, the MIT Solar Wind Group for providing the solar wind plasma data and G.D. Reeves for providing Los Alamos National Laboratory spacecraft data. J.R.T. was supported by PPARC grant GR/J 88937. Topical Editor K. -H. Glaßmeier thanks K. Kauristie and R. L. McPherron for their help in evaluating this paper.-->
Emery Barbara A.
Hughes Terrence J.
Knipp Delores J.
Lester Mark
Lühr Hermann
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