Time filter

Source Type

Etobicoke, Canada

In this paper, hourly median value of ionosonde measurements: peak height F2-layer (hmF2), F2-layer critical frequency(fOF2) and propagation factor M (3000) F 2 made at near-equatorial dip latitude, Ouagadougou, Burkina Faso (12°N, 1.5°W; dip: 1.5°N) and relevant F2-layer parameters: thickness parameter (B0), electron temperature (T e), ion temperature (Ti), total electron content (TEC) and electron density (Ne) (at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial electrodynamics on the diurnal structure of F 2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. It is demonstrated that the month-by-month morphological patterns between vertical E × B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-B0. IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Examination of the association between measured f0F2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Oyekola O.S.,307 143 Eighth Street
Advances in Space Research | Year: 2011

Measurements of the critical frequency, foF2 recorded over Ibadan: 7.4°N, 3.9°E (geographic), 6°S (dip angle) have been compared with the International Reference Ionosphere (IRI-2007) model for solar maximum geomagnetically quiet conditions, with a view to determining what modifications might bring about better predictions for the model. Our results reveal that the present version of IRI essentially reproduces diurnal trends and the general features of the experimental observations for all seasons, except for nighttime June solstice periods, which the model seriously overestimated. The model errors ranging from 50% to 125% over the four seasons considered in this study. It is also indicated that the percentage relative deviations between the observed and the modeled values vary approximately from -11% to 12% (March), -34% to 11% (June), -16% to 12% (September), and -10% to 13% (December). An unexpected feature of foF2 is obvious and remarkable reduction in values during nighttime June solstice periods compared to that in other seasons. Relationship between equatorial vertical drift and foF2 is also investigated. However, cross correlation analysis reveals strong anti-correlation between vertical drift and critical frequency during the daytime hours, but exceptionally opposite is the case for the nighttime sector. The discrepancies which are noted, particularly during June solstice season are attributed to processes most likely within the thermosphere and from meteorological influences during quiet magnetic conditions. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

Oyekola O.S.,307 143 Eighth Street | Fagundes P.R.,University of Paraiba Valley
Earth, Planets and Space | Year: 2012

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 (h mF2), F2 layer peak electron density (N mF2/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 R z12 = 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 MioooF2, respectively. The model results have errors ranging from approximately 8-15%, 9-17%, and 3-5%, respectively, for hmF2, N mF2, 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 hmF 2, 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. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Oyekola O.S.,307 143 Eighth Street | Fagundes P.R.,University of Paraiba Valley
Earth, Planets and Space | Year: 2012

Observations of the F2-layer critical frequency (f 0F2), peak height F2-layer (hmF 2) and propagation factor (M3000F2) recorded near dip-equator Ouagadougou, Burkina Faso (12.4°N, 358.5°E; dip latitude: 1.5°N) have been validated against the International Reference Ionosphere (IRI-2007) model during low (1987) and high (1990) solar activity and undisturbed conditions for four different seasons, with a view to enhance the predictability of the IRI. The results illustrated that URSI option for h mF2 and CCIR option for M3000F2 portray remarkably well the morphological trends and replicate mostly the diurnal salient features of the experimental data at low and high solar activity periods. In contrast, both URSI and CCIR models of f0F2 also reproduce diurnal and seasonal patterns and outstanding features of observational data surprisingly well for solar minimum conditions except July; whereas we found considerable disparities between model and data during solar cycle maximum. The total model error ranging from approximately 6-8% (h mF2), 13-38% (fQF2) and 8-29% (hmF2), 12-44% (f0F2), respectively for low and high flux year, but roughly comparable at 3-7% for M 3000F2 at low and high solar activity. Our observations indicate higher values of foF2 deviations compared to prior calculated differences obtained for the low-latitude region over Indian and Asian. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Discover hidden collaborations