ADENIJI-ADELE RASAQ ADEWEMIMO

Physics

At the Physics department office

Appointment on Visitation important

Topic: A COMPARATIVE ANALYSIS OF MAXIMUM USABLE FREQUENCY LEADING TO A SINGLE-STATION MODEL FOR THE AFRICAN EQUATORIAL IONOSPHERE

Description:

The maximum usable frequency (MUF) is an important parameter in the design and operation of radio systems operating within the high frequency (HF) band (3-30 MHz) for long-distance communications. 

This study presents a station specific MUF model for the Dakar station. Leading to this aim, a comparative analysis of MUF at three African equatorial stations [Dakar (14.8oN, 17.4oW, dip: 11.4oN); Djibouti (11.5oN, 42.8oE, dip: 7.2oN) and Ouagadougou (12.4oN, 1.5oW, dip: 5.4oN)] and two mid-latitude stations [Johannesburg (26.17oS, 28.03oE, dip: 64oS) and Slough (54.5oN, 0.6oW, dip: 68.8oN)] was carried out. In this work, 22 to 33 years of hourly values of the critical frequency of F2-layer (foF2) and the propagation factor of F2-layer (M(3000)F2) were used to determine the corresponding basic MUF {MUF = foF2*M(3000)F2} data.

The primary data-sets were scaled at the five ionosonde stations over a period spanning the interval between peaks of solar cycles 19 and 22. Other data used in this study include mean monthly sunspot numbers (SSN) {1957-1989} and yearly magnetic inclination values {1957-1989}.

Solar-cycle periodicity and MUF build-up-rate as functions of diurnal variation were investigated using hourly means MUF values. Fourier analysis was used to determine which of the temporal variations predominates at different epochs of the solar cycle and hence critical to HF radio propagation. Curve-fitting by a Sum of Gaussians was used to determine the minimum number of Gaussians that approximate given MUF data sets for the Dakar station (r = 0.75). Results showed that characterisation of MUF on the diurnal scale revealed the presence of pre- and post-dawn peaks with a depression occurring between 0700 and 0800 hours during December solstice. During June solstice, MUF peaks at post-dawn and post-noon. Longitudinal differences in MUF variability were observed between the equatorial stations. Latitudinal differences in MUF variability were observed between the equatorial and the mid-latitude stations. Build-up-rate of MUF is found to follow the trend of solar zenith angle on daily basis and also showed solar-cycle dependence at all seasons for the stations. Intervals between successive maxima of annual hourly mean MUF showed that the mean periodicity of the solar-cycle ranges from 9 to 13 years. Fourier analyses of diurnal MUF indicated that the 24-hourly (diurnal) component is the most important at all the stations while the analysis of monthly MUF revealed the importance of the annual (12-monthly) component. The analytically developed MUF empirical model (with 95% confidence bounds) compares well with International Reference Ionosphere (IRI) (PropLab Pro) and Voice of America Coverage Analysis Program (VOACAP) MUF models. The results obtained in this study will enhance understanding of MUF variability leading to improved HF broadcasting, advance MUF prediction and augment MUF data base in the African equatorial region.

#	Certificate	School	Year
1.	Ph.D (IONOSPHERIC AND RADIO PROPAGATION PHYSICS.)	PHYSICS, LAGOS STATE UNIVERSITY, OJO.	2017

ADENIJI-ADELE RASAQ is a Lecturer II at the Department of Physics

ADENIJI-ADELE has a Ph.D in IONOSPHERIC AND RADIO PROPAGATION PHYSICS. from PHYSICS, LAGOS STATE UNIVERSITY, OJO.