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Ann. Geophys., 16, 721-730, 1998
www.ann-geophys.net/16/721/1998/
© European Geosciences Union 1998
Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar
E. Blanc1 and E. Houngninou2
1Laboratoire de Detection et de Géophysique, Commissariat à l'Energie Atomique, Bruyères le Chatel, France
Fax: + 01 69 26 70 23; e-mail: blanc@ldg. bruyeres.cea.fr
2Département de physique, Université d'Abidjan, Ivory Coast
Abstract. HF radar measurements were performed near the
magnetic equator in Africa (Korhogo 9°24'63''N–5°37'38''W) during the
International Equatorial Electrojet Year (1993–1994). The HF radar is a
high-resolution zenithal radar. It gives ionograms, Doppler spectra and echo
parameters at several frequencies simultaneously. This paper presents a
comparative study of the daytime ionospheric structures observed during 3 days
selected as representative of different magnetic conditions, given by
magnetometer measurements. Broad Doppler spectra, large echo width, and
amplitude fluctuations revealed small-scale instability processes up to the
F-region peak. The height variations measured at different altitudes showed
gravity waves and larger-scale disturbances related to solar daytime influence
and equatorial electric fields. The possibility of retrieving the ionospheric
electric fields from these Doppler or height variation measurements in the
presence of the other possible equatorial ionospheric disturbances is discussed.
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