Department Of Physics
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The Department provides tutorial and/or research courses at undergraduate and postgraduate levels leading to the award of the degrees of Bachelor of Sciences (Honours) (B.Sc.), the Master of Science (M.Sc.), Master of Philosophy (M.Phil.) and Doctor of Philosophy (Ph.D.) in Physics respectively. Physics is one of the basic experimental physical sciences.
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Browsing Department Of Physics by Author "Adeloye, A.B."
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- ItemOpen AccessAn evaluation of the IRI-2007 storm time model at low latitude stations(Elsevier Ltd, 2013) Oyeyemi, E.O.; Adewale, A.B.; Adeloye, A.B.; Olugbon, B.This paper discusses the ability of the International Reference Ionosphere IRI-2007 storm time model to predict foF2 ionospheric parameter during geomagnetic storm periods. Experimental data (based on availability) from two low latitude stations: Vanimo (geographic coordinates, 2.7°S, 141.3°E, magnetic coordinates, 12.3°S, 212.50°E) and Darwin (geographic coordinates, 12.45°S, 130.95°E, magnetic coordinates, 22.9°S, 202.7°E) during nine storms that occurred in 2000 (Rz12 = 119), 2001(Rz12 = 111) and 2003 (Rz12 = 64) are compared with those obtained by the IRI-2007 storm model. The results obtained show that the percentage deviation between the experimental and IRI predicted foF2 values during these storm periods is as high as 100% during the main and recovery phases. Based on the values of “relative deviation module mean” (RDMM) obtained (i.e. between 0.08 and 0.60), it is observed that there is a reasonable to poor agreement between measured foF2 values and the IRI-storm model prediction values during main and recovery phases of the storms under investigation. As a result, in addition to other studies that have been carried out from different sectors, more studies are required to be carried out. This will enable IRI community to improve on the present performance of the model. In general, the IRI-storm model predictions follow normal trend of the foF2 measured values but does not reproduce well the measured values.
- ItemOpen AccessLow solar activity variability and IRI 2007 predictability of equatorial Africa GPS TEC(Elsevier Ltd, 2011) Adewale, A.O.; E.O. Oyeyemi, E.O.; Cilliers, P.J.; McKinnell, L.A.; Adeloye, A.B.Diurnal, seasonal and latitudinal variations of Vertical Total Electron Content (VTEC) over the equatorial region of the African continent and a comparison with IRI-2007 derived TEC (IRI-TEC), using all three options (namely; NeQuick, IRI01-corr and IRI-2001), are presented in this paper. The variability and comparison are presented for 2009, a year of low solar activity, using data from thirteen Global Positioning System (GPS) receivers. VTEC values were grouped into four seasons namely March Equinox (February, March, April), June Solstice (May, June, July), September Equinox (August, September, October), and December Solstice (November, December, January). VTEC generally increases from 06h00 LT and reaches its maximum value at approximately 15h00–17h00 LT during all seasons and at all locations. The NeQuick and IRI01-corr options of the IRI model predict reasonably well the observed diurnal and seasonal variation patterns of VTEC values. However, the IRI-2001 option gave a relatively poor prediction when compared with the other options. The post-midnight and post-sunset deviations between modeled and observed VTEC could arise because NmF2 or the shape of the electron density profile, or both, are not well predicted by the model; hence some improvements are still required in order to obtain improved predictions of TEC over the equatorial region of the Africa sector.
- ItemOpen AccessResponses of equatorial F region to different geomagnetic storms observed by GPS in the African sector(JOURNAL OF GEOPHYSICAL RESEARCH, 2011) Adewale, A.O.; Oyeyemi, E.O.; Adeloye, A.B.; Ngwira, C.M.; Athieno, R.This article presents the first results regarding the investigation of the response of the equatorial ionospheric F region in the African sector during geomagnetic storm periods between April 2000 and November 2007 using GPS‐derived vertical total electron content observed at Libreville, Gabon (0.35°N, 9.67°E, dip latitude −8.05°S). We performed a superposed epoch analysis of the storms by defining the start time of the epoch as the storm onset time. During geomagnetic storms, the altered electric fields contribute significantly to the occurrence of negative and positive ionospheric storm effects. Our results showed that the positive storm effects are more prevalent than the negative storm effects and generally last longer irrespective of storm onset times. Also, the positive storm effects are most pronounced in the daytime than in the premidnight and postmidnight periods.
- ItemOpen AccessA study of L-band scintillations and total electron content at an equatorial station, Lagos, Nigeri(RADIO SCIENCE, 2012) Adewale, A.O.; Oyeyemi, E.O.; Adeloye, A.B.; Mitchell, C.N.; Rose, J.A.R.; Cilliers, P. J.In this paper we present the first results from measurements of scintillation and total electron content (TEC) from an equatorial station, Lagos (Latitude 6.5 N, Longitude 3.4 E, magnetic latitude 3.03 S), Nigeria, using a Novatel GSV4004B GPS ionospheric scintillation and TEC monitor. Details are presented for data collected between February 2010 and August 2010. The results show that the presence of some large scale depletions of TEC or plasma bubbles may be noted during the evening hours and that TEC depletions correspond to increased rate of change of TEC (ROT). This confirms that plasma bubbles are associated with large scale irregularities. It is also established that enhanced amplitude scintillation (S4) corresponds quite well with TEC depletions and increases in ROT. The diurnal and seasonal percentage occurrence for different levels of scintillation activity has peaks in the equinox months (March and April) at 23:00 LT
- ItemOpen AccessVariability of foF2 in the African equatorial ionosphere(Elsevier Ltd, 2010) Adewale, A.O.; Akala, A.O.; Oyeyemi, E.O.; Somoye, E.O.; Adeloye, A.B.This paper presents the impact of diurnal, seasonal and solar activity effects on the variability of ionospheric foF2 in the African equatorial latitude. Three African ionospheric stations; Dakar (14.8°N, 17.4°W, dip: 11.4°N), Ouagadougou (12.4°N, 1.5°W, dip: 2.8°N) and Djibouti (11.5°N, 42.8°E, dip: 7.2°N) were considered for the investigation. The overall aim is to provide African inputs that will be of assistance at improving existing forecasting models. The diurnal analysis revealed that the ionospheric critical frequency (foF2) is more susceptible to variability during the night-time than the day-time, with two peaks in the range; 18–38% during post-sunset hours and 35– 55% during post-midnight hours. The seasonal and solar activity analyses showed a post-sunset September Equinox maximum and June Solstice maximum of foF2 variability in all the stations for all seasons. At all the stations, foF2 variability was high for low solar activity year. Overall, we concluded that equatorial foF2 variability increases with decreasing solar activity during night-time.