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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 10
Ann. Geophys., 27, 3861–3873, 2009
https://doi.org/10.5194/angeo-27-3861-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 3861–3873, 2009
https://doi.org/10.5194/angeo-27-3861-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  12 Oct 2009

12 Oct 2009

Characteristics of the ionospheric total electron content of the equatorial ionization anomaly in the Asian-Australian region during 1996–2004

Biqiang Zhao1, Weixing Wan1, Libo Liu1, and Zhipeng Ren1,2,3 Biqiang Zhao et al.
  • 1Beijing National Observatory of Space Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
  • 2Wuhan Institute of Physics and Mathematics, CAS, Wuhan, China
  • 3Graduate School of Chinese Academy of Sciences, Beijing, China

Abstract. Ionospheric total electron content (TEC) of the equatorial ionization anomaly (EIA) is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a network of receivers around the Asian-Australian region during 1996–2004. The latitude, occurrence time, strength of the most developed EIA crest, and crest-to-trough ratio (CTR) for both the noon and post-sunset sector obtained from a daily TEC contour map have been used to study the solar cycle variations of EIA in the Asian-Australian region. The results reveal that semiannual and seasonal variations were the dominant factor that controls the morphology of the EIA structure which can be identified in the past studies (e.g. Wu et al., 2008). It is also found that the latitude and local time position of the anomaly crest show a hemispheric asymmetry because (a) The northern crest of EIA is expanded during the equinox indicating a weak semiannual variation while the southern crest is inhibited during June–August presenting a strong seasonal variation, and (b) The local time of the northern crest appears ~1.3 h earlier than that of the southern crest in June while showing no difference at December. Solar activity dependence is more evident in the EIA crest region than in the EIA trough region and least in the post-sunset sector at equinox. A seasonal linear relationship is derived between the post-sunset CTR and solar flux, which should be caused by the solar-dependant equatorial E×B vertical drift.

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