Browsing by Author "Bello, S.A"

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    Ionospheric Minimum Frequency Variability over Ilorin
    (BAJOPMAS Journal, 2026-02) Bello, S.A; Adeniyi, J.O.; Oladipo, M.O; Shehu J.S.; Sharafa, S.B.; Kazeem, A.K.; Akinyemi,G. A.; Yusuf, K.A
    Using ground-based Digisonde records from the University of Ilorin Ionospheric Observatory (8.5° N, 4.5° E) over the year 2010, this study examined the equatorial ionospheric minimum frequency (𝑓𝑚𝑖𝑛) over Ilorin, Nigeria. We looked at both seasonal and diurnal changes in 𝑓𝑚𝑖𝑛. From a pre-dawn minimum to an afternoon maximum, the diurnal pattern shows a consistent increase, which is followed by a fall after sunset. Seasonal findings reveal significant daytime variability between 1200 and 1400 UT (LT = UT + 1 h), with the highest noon peak observed during the equinoxes and the lowest during the solstices. Midday peak values ranged between 2.05 and 2.7 MHz across the months studied. The increased electron density in the ionospheric D-layer is responsible for these observed peaks.
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    Variations of B0 and B1 with the solar quiet Sq-current system and comparison with IRI-2012 model at Ilorin
    (2017-07-15) Bello, S.A; Abdullah, M.; Hamid, N.S.A; Yoshikawa, A.; Olawepo, A.O.
    The ionospheric thickness (B0) and shape (B1) are bottomside profile parameters introduced by the International Reference Ionosphere (IRI) model. We have validated these parameters with the latest version of the IRI-2012 model and compared them with the solar quiet of geomagnetic H-component (SqH). The B0, B1 and SqH are calculated from the measurements obtained from digisonde DPS-4 sounder and the Magnetic Data Acquisition System (MAGDAS) magnetometer, respectively at Ilorin (geo latitude 8.50°N, geo longitude 4.68°E, and Magnetic dip 4.1°S) an equatorial station in the African sector. The study was for the year 2010, a year of low solar activity (with 27-day averaged solar index, F10.7 = 80 sfu). The results show that B0 for the entire months was higher during the daytime than during the night time. On the other hand, the magnitude of B1during the daytime period is lower than nighttime values and exhibit oscillatory pattern. By comparing the experimental observations of the profile parameters with the IRI-2012 model prediction, we found that B0 was fairly represented by the IRI model options during the nighttime period while discrepancies exist between the model estimates and the experimental values during the morning till midday. A close agreement exists between the observed B1 values and IRI model options. We observed a positive and significant correlation coefficient between B0 and SqH indicating a plausible relationship between these parameters while a weak and negative correlation coefficient between B1 and SqH was observed. We concluded that the difference in the relationship of SqH and the profile parameters B0 and B1 observed can be attributed to their sensitivity to the electric field which is responsible for the E × B drift which in turn modulate the height of the F2.