On equatorial geophysics studies: A review on the IGRGEA results during the last decade

Christine Amory-Mazaudier, A. Kobea, P. Vila, A. Achy-Séka, E. Blanc, K. Boka, J. Bouvet, J. F. Cécile, Y. Cohen, J. J. Curto, M. Dukhan, V. Doumouya, O. Fambitakoye, T. Farges, C. Goutelard, E. Guisso, R. Hanbaba, E. Houngninou, E. Kone, P. Lassudrie-DuchesneC. Lathuillere, Y. Leroux, M. Menvielle, E. Obrou, M. Petitdidier, S. O. Ogunade, C. A. Onwumechili, D. Rees, E. Sambou, M. Sow, J. Vassal

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During the years 1993-1994, a continuous campaign of measurements has been held in the frame of the International Equatorial Electrojet Year (IEEY) with a network of 10 magneto-telluric stations and a network of three ionosondes. Other instruments have participated during shorter periods, HF radar and optical Fabry-Perot 630 nm interferometer. After the IEEY campaigns, the International Group of Research in Geophysics in Europe Africa (IGRGEA created in January 1995), has organized the research in geophysics. This paper report the main results of the IGRGEA during the last decade at local, regional and planetary scales. At a local scale, the HF radar data highlighted the complex structure of echoes in the equatorial zone and allowed to explain the "necklace" echoes as due to oblique propagation into the type I instability levels. This radar observed atmospheric storm electric field discharges at Es layer for the daytime and Equatorial Spread F at night-time. A series of original results concern Doppler spectra and the electric field change on plasma drifts across the ionosphere, gravity waves effects as well the ESF multi-process sources. At a regional scale, magnetic data were used to parametrize the Equatorial Electrojet (EEJ). Ionospheric data, magnetic data and UARS satellite were brought together as input parameters of the Richmond's EEJ model to reproduce the EEJ and the magnetic field variations associated to EEJ. The comparisons between magnetic data, and the magnetic field computed from the physical model and from the parametrization of the EEJ are all in good agreement. Ionosonde data were included in the IRI. Ionosonde data revealed the field aligned f0F2 crests of ionization at mid morning and early afternoon hours. Measurements of equatorial night-time wind variations, obtained for the first time over African equatorial zone with the Fabry-Perot interferometer, shown the strong variability of atmospheric winds. At a planetary scale, the parametrization of the EEJ was done using the magnetometers chain involved during IEEY in the three longitude sectors. Finally, we present the results on electrodynamic coupling between high and low latitudes with overshielding or shielding events.

Idioma originalAnglès
Pàgines (de-a)301-313
Nombre de pàgines13
RevistaJournal of Atmospheric and Solar-Terrestrial Physics
Estat de la publicacióPublicada - de març 2005
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