TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 6), pp. 567-575, 2012

On the variations of ionospheric parameters made at a near equatorial station in the African longitude sector: IRI validation with the experimental observations

O. S. Oyekola1 and P. R. Fagundes2

1307-143 Eighth Street, Etobicoke, Ontario, M8V 3C8, Canada
2Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, Sao Paulo, Brazil

(Received July 21, 2011; Revised October 10, 2011; Accepted October 15, 2011; Online published July 27, 2012)

Abstract: We examine the main morphological patterns and climatological behaviour of equatorial F2 region over African sector using hourly observational values of F2 peak height of maximum electron density (hmF2), F2 layer peak electron density (NmF2/foF2), and propagation factor (M3000F2) hitherto made by the Ibadan ionosonde at 7.4°N, 3.9°E, dip latitude 2.3°S, in Nigeria; between January to December 1958, during a period of high solar activity (yearly averaged Rz12 = 190 units) and magnetically quiet conditions (Kp ≤ 3). A direct comparison between these measurements and the International Reference Ionosphere 2007 (IRI-2007) model-predictions are also made. The results of comparisons illustrate that good advancement has been made but reveal some important discrepancies. The trends in the experimental data are found to be in excellent agreement with the trends in the simulation results for maximum electron density and propagation factor, but fair-to-good for F2 layer peak altitude. The model is unable to capture the sharp postsunset and predawn enhancements in hmF2 and M3000F2, respectively. The model results have errors ranging from approximately 8-15%, 9-17%, and 3-5%, respectively, for hmF2, NmF2, and M3000F2. On average, the percent absolute relative difference of the model from the experimental observations varies from about 0-20%, 0-30%, and 0-10% for hmF2, NmF2, and M3000F2, in that order. Our results are essentially consistent with other equatorial and low-latitude ground-based measurements over South America, India, and Southeast Asia.
Key words: Equatorial-ionosphere, ionosonde-data, IRI-2007, modeling and forecasting, ionospheric-parameter.

Corresponding author E-mail: oyedemio@yahoo.com

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