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AGU: Journal of Geophysical Research, Space Physics

 

Keywords

  • Equatorial ionosphere
  • solar cycle
  • vertical drifts
  • F region

Index Terms

  • Ionosphere: Equatorial ionosphere
  • Ionosphere: Electric fields
  • Ionosphere: Ionospheric dynamics
  • Ionosphere: Ionospheric irregularities
  • Ionosphere: Instruments and techniques
Abstract
Cited By (5)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, A12306, 12 PP., 2007
doi:10.1029/2007JA012560

Seasonal and solar cycle variability in F-region vertical plasma drifts over Ouagadougou

O. S. Oyekola

Department of Physics, University of Ibadan, Ibadan, Nigeria

Akin Ojo

Department of Physics, Lagos State University, Ojo, Lagos, Nigeria

J. Akinrimisi

Department of Physics, University of Lagos, Lagos, Nigeria

E. R. dePaula

Institute de Pesquisas Espaciasis-INPE, Sao Paulo, Brazil

F-region vertical drifts were made using ionosonde for the Africa equatorial station Ouagadougou (12°N, 1.5°W; 5.9°N dip) from 3 a of data during January 1987 to December 1989 for solar cycle minimum, medium, and maximum conditions (F10.7 = 85, 141, and 214, respectively) under geomagnetic quiet-time. The variations are found to be dominated by the characteristics morning peak and evening prereversal enhancement (PRE) velocities. Seasonal and solar cycle effects are prominent near the dusk sector with an increase of PRE from solar minimum to maximum. The average equinoctial evening prereversal enhancement increases by almost a factor of three from low to high flux. On the average, the values of daytime and nighttime ionosonde-derived vertical drifts are smaller by about a factor of four than the magnitude often mentioned in publication for equatorial regions from other experimental techniques. In addition, the morning peak velocities maximize between about 0830–0930 LT with typical values of 12–18 m/s. In contrast, PRE have largest amplitude between about 1700–2200 LT with typical values of 5–10 m/s. The morning reversal times do not reveal any dependence on season and solar cycle; but the most probable time of occurrence is around 0530 LT. The evening reversal times are in excellent agreements for the three levels of solar activity periods apart from June solstice that exhibit considerable variations. The most likely time of occurrence is near 2000 LT. Of importance, the link between the onset / inhibition parameters of postsunset irregularities over Ouagadougou indicate anti-correlations with solar variability.

Received 25 May 2007; accepted 10 October 2007; published 29 December 2007.

Citation: Oyekola, O. S., A. Ojo, J. Akinrimisi, and E. R. dePaula (2007), Seasonal and solar cycle variability in F-region vertical plasma drifts over Ouagadougou, J. Geophys. Res., 112, A12306, doi:10.1029/2007JA012560.

Cited By

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