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Ann. Geophys., 16, 658-666, 1998
www.ann-geophys.net/16/658/1998/
© European Geosciences Union 1998
Equatorial electrojet at African longitudes: first results from magnetic measurements
V. Doumouya1, J. Vassal2, Y. Cohen3, O. Fambitakoye2, and M. Menvielle4
1Laboratoire de Physique de l'Atmosphère, Université d'Abidjan, Abidjan, Ivory Coast
2Laboratoire de Géophysique, ORSTOM, 32 av. Henri-Varagnat, F-93143 Bondy Cedex, France
3Laboratoire de Géomagnétisme, IPGP, B89, 4 Place Jussieu, F-75252 Paris Cedex 05, France
4CETP CNRS, 4 Avenue de Neptune, F-94107 Saint-Maur Des Fossés Cedex,France
Abstract. In the framework of the French participation
in the International Equatorial Electrojet Year (IEEY), ten magnetotelluric
stations were installed between November 1992 and November 1994 along a
1200-km-long meridian profile, between Lamto (latitude 6.2°N, Côte d'Ivoire)
to the south and Tombouctou (latitude 16.7°N, Mali) to the north. These
stations measured digitally the three components of the magnetic field and the
two components of the telluric electric field, and operated over a period of 20
months. The magnetic data is used to study the features of the equatorial
electrojet (EEJ) in West African longitude. The measurement of the telluric
electric field variations will be presented elsewhere. Hourly mean values are
used to study the morphological structure of the regular diurnal variation SR
of the three components (H, D, and Z) of the earth magnetic
field and to characterize the EEJ during magnetically quiet days. The
occurrences of the counter-electrojet (CEJ) are set forth, emphasizing its
seasonal variability. Assumed to be a current ribbon, the EEJ main parameters
(the position of its center, its width, and the amplitude of its current density
at the center) are determined. A preliminary analysis of the time variations of
these parameters is presented over period of 20 months (from January 1993 to
August 1994). Results are compared with those obtained during previous
experiments of the same kind.
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