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Ann. Geophys., 23, 693-706, 2005
www.ann-geophys.net/23/693/2005/
© European Geosciences Union 2005
Responses of equatorial anomaly to the October-November 2003 superstorms
B. Zhao1,2,3, W. Wan1, and L. Liu1
1Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2Wuhan Institute of Physics and Mathematics, CAS, Wuhan 430071, China
3Graduate School of Chinese Academy of Sciences, Beijing, China
Abstract. The responses of Equatorial Ionization Anomaly (EIA) to
the superstorms of October-November 2003 were investigated using the total
electron content (TEC) measured with global positioning system (GPS)
receivers in China, Southeast Asia, Australian (CSAA), and the American regions.
Enhanced EIA was seen to be correlated with the southward turning of the
interplanetary magnetic field Bz. In both the CSAA and American regions, EIA
was intensified, corresponding to a large increase in the F-layer peak height
(hmF2) measured by ionosonde and digisonde at middle and equatorial
latitudes. However, the enhanced EIA was shown to be more significant during the
daytime in the American region, which was associated with a series of large
substorms when Bz was stable southward. The prompt penetration electric field
and the wind disturbances dynamo electric field are suggested to be responsible
for this observation according to current theory, although some features cannot
be totally decipherable. Both the ionogram and magnetometer data show
the existence of a weak shielding effect whose effect still needs further
study. A clear asymmetric ionospheric response was shown in our TEC
observations, even though it was only one month after autumnal equinox. The
southern EIA crest was totally obliterated on 29 and 30 October in the CSAA
region and on 31 October in the American region. Ion temperatures from the
Defense Meteorological Satellite Program (DMSP) spacecraft revealed that
the unequal energy injection at the polar region might be the reason for this
effect. It is concluded that different physical processes have varying
degrees of importance on the evolution of EIA in the CSAA and American regions.
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