[01] Onori E. O., Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [02] Somoye E. O., Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [03] Ogungbe A. S., Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [04] Ogabi C. O., Department of Physics, Lagos State University, Ojo, Lagos, Nigeria. [05] Ogwala A., Department of Physics, Lagos State University, Ojo, Lagos, Nigeria.

Harmonic analysis of the response of the critical frequency of the E and F2 layers to solar activity during year of maximum, moderate and minimum solar activity 1958, 1973 and 1965 respectively at Ibadan (7.400 N, 3.900 E, 60 S dip) are studied. The critical frequencies of the E and F2 layers (foE and foF2) were use as ionospheric parameters for the E and F2 layers while Zurich sunspot number (Rz) was used as index of solar activity in this work. The monthly mean values of the critical frequency of the E and F2 layer were computed and harmonic analysis carried out on the data. The critical frequency of the E layer is found to respond more rapidly to solar activity than that of the F2 layer. The first harmonic of diurnal variation of foE and foF2 always predominate other harmonics for the three years under investigation, confirming diurnal variation.

Critical Frequency of E Layer (foE), Critical Frequency of F2 Layer (foF2), Sunspot Number (Rz), Harmonic Analysis

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