[01] Emmanuel O. Somoye, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [02] Eugene O. Onori, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [03] Abiola S. Ogungbe, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [04] Cornelius O. Ogabi, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [05] Aghogho Ogwala, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [06] Oluwafunmi O. Ometan, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [07] Rasaq A. Adeniji-Adele, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [08] Enerst E. Iheonu, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [09] Kayode S. Oluyo, Department of Physics and Electronics, Yaba Technical College, Yaba, Lagos, Nigeria. [10] Adesina T. Sode, Department of Physics, Lagos State University, Ojo, Lagos, Nigeria.

The characterization of the day – to – day variability (VR) of the critical frequency of F1 (foF1) layer on diurnal and seasonal scale is undertaken at Ibadan (7.4°N, 3.9°E, 6°S dip) in the African sector during low solar activity (LSA) and moderate solar activity (MSA). The latitudinal effect on foF1 VR is also investigated by combining data from Singapore (1.3°N, 103.8°E, 17.6°S dip) in the East Asian sector and Slough (51.5°N, 359.4°E, 66.5°N dip) in the European sector. The variability of foF1 is found to be of order (1-3.8%) during LSA and (2-9%) during MSA. On the seasonal scale foF1 VR is greater during March Equinox for both epochs. Comparison of foF1 VR with foE VR and foF2 VR shows that foF1 VR is of the same order of magnitude (0.5 to 4%) during LSA and slightly greater than foE VR (1.5 - 6%) during MSA, in general. It is less than foF2 VR (2 – 15%) during both epochs. Daytime (10:00 h -16:00 h) foF1 VR is greater at Singapore (1.8 – 5.8%) and at Ibadan (1.8 – 5.8%) than at Slough (2.2 – 4.0%), on a general note. While pre-sunrise and post-sunset peaks are apparent at Slough, they are not at Singapore and Ibadan.

foF1 Variability, Solar Activity, F1 Layer, Latitude

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