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Volume 35, issue 3
Ann. Geophys., 35, 535–545, 2017
https://doi.org/10.5194/angeo-35-535-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: The 14th International Symposium on Equatorial Aeronomy

Ann. Geophys., 35, 535–545, 2017
https://doi.org/10.5194/angeo-35-535-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 07 Apr 2017

Regular paper | 07 Apr 2017

Longitudinal variation of equatorial electrojet and the occurrence of its counter electrojet

A. Babatunde Rabiu1, Olanike Olufunmilayo Folarin1,2, Teiji Uozumi3, Nurul Shazana Abdul Hamid4, and Akimasa Yoshikawa3 A. Babatunde Rabiu et al.
  • 1Centre for Atmospheric Research, National Space Research and Development Agency, Anyigba, Nigeria
  • 2Ionospheric and Space Physics Laboratory, Department of Physics, University of Lagos, Akoka, Lagos State, Nigeria
  • 3International Center for Space Weather Science and Education ICSWSE, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
  • 4National University of Malaysia, Faculty of Science & Technology, Selangor, Malaysia

Abstract. We examined the longitudinal variability of the equatorial electrojet (EEJ) and the occurrence of its counter electrojet (CEJ) using the available records of the horizontal component H of the geomagnetic field simultaneously recorded in the year 2009 (mean annual sunspot number Rz  =  3.1) along the magnetic equator in the South American, African, and Philippine sectors. Our results indicate that the EEJ undergoes variability from one longitudinal representative station to another, with the strongest EEJ of about 192.5 nT at the South American axis at Huancayo and a minimum peak of 40.7 nT at Ilorin in western Africa. Obtained longitudinal inequality in the EEJ was explicable in terms of the effects of local winds, dynamics of migratory tides, propagating diurnal tide, and meridional winds. The African stations of Ilorin and Addis Ababa registered the greatest % of CEJ occurrence. Huancayo in South America, with the strongest electrojet strength, was found to have the least occurrence of the CEJ. It is suggested that activities that support strong EEJ inhibits the occurrence of the CEJ. Percentage of occurrence of the CEJ varied with seasons across the longitudes. The order of seasonal variation of morning occurrence does not tally with the evening occurrence order at any station. A semiannual equinoctial maximum in percentage of morning occurrence of the CEJ was obtained at Huancayo and Addis Ababa. Only Addis Ababa recorded equal equinoctial maxima in percentage of evening occurrence of the CEJ. The seasonal distribution of the occurrences of the CEJ at different time regimes implies a seasonal variability of causative mechanisms responsible for the occurrence of the CEJ.

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This work examined the longitudinal variability of the equatorial electrojet (EEJ) and the occurrence of its counter electrojet (CEJ) using the available records of the horizontal component H of the geomagnetic field simultaneously recorded in the year 2009 along the magnetic equator in South American, African, and Philippine sectors. Our results indicate that the EEJ and CEJ undergo longitudinal variability. More ground observation data points are required in the African equatorial zone.
This work examined the longitudinal variability of the equatorial electrojet (EEJ) and the...
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