Articles | Volume 16, issue 6
Ann. Geophys., 16, 711–720, 1998

Special issue: Electrojet

Ann. Geophys., 16, 711–720, 1998

  30 Jun 1998

30 Jun 1998

Non-trough foF2 enhancements at near-equatorial dip latitudes

E. Sambou1, P. M. Vila2, and A. T. Kobea3 E. Sambou et al.
  • 1Département de Physique, Université C. Anta Diop, Dakar-Fann, Senegal
  • 2Centre d'Étude des Environnements Terrestres et Planétaires (CETP), 4 Avenue de Neptune, F-94107, Saint-Maur-des-Fossés, France
  • 3Département de Physique de l'Atmosphère, Université de Cocody, 22 BP582, Abidjan 22, Côte d'Ivoire

Abstract. Fine resolution series from three equatorial ionosondes of the IEEY network in West Africa have revealed small-scale daytime peak F2 structures, superposed on the slowly varying minimum or "trough" distribution in the ±5° magnetic latitude zone. We report this new morphology, concentrating on foF2 enhancements of two types: near-equatorial crests (which travel either northwards or southwards) and magnetic field-aligned domes, whose onsets last only tens of minutes. Both types are observed to start at mid-morning or early afternoon hours. We relate their occurrence with the available variations of Vz=E × B upward drift which feeds the equatorial plasma fountain. We suggest the foF2 enhancements to be triggered by brief slow-downs of the Vz velocity near F2 peak altitude in our West African sector. Their short latitude extent differentiates them from the larger-scale tropical crest system. Further analysis of these features should lead to weather-like models of the low latitude ionosphere variations, where unstable local coupling between processes seems to be the trigger.

Key words. Ionosphere (Equatorial ionosphere · Ionosphere-atmosphere interaction · Plasma temperature and density)

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