Browsing by Author "Baki, Paul"

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African Equatorial GPS Scintillations during the Minimum and Ascending Phases of Solar Cycle 24
(2014) Andrew, Akala; Groves, KM; Amaeshi, Larry; Idolor, Raphael; Okoro, Ekemini; Carrano, Charles; Bridgwood, Christopher; Baki, Paul; Dujanga, Florence; Doherty, Patricia
This study characterizes African equatorial scintillations at L-band frequency during the minimum and ascending phases of solar cycle 24. Three years' (2009-2011) of amplitude scintillation data from three African equatorial GPS stations namely; Lagos (3.48oN, 3.27oE, mag. lat: 3.04oS), Nigeria; Nairobi (1.30oS, 36.80oE, mag. lat: 8.03oS), Kenya; and Kampala (0.30oN, 32.50oE, mag. lat: 9.26oS), Uganda were used for the investigation. We grouped the data on daily, monthly, seasonal, and yearly scales at three levels of scintillation (weak (0.3<=S4<0.4), moderate (0.4<=S4<0.7), and intense (S4>=0.7)), and adopted three data cut-off criteria. Scintillations exhibit daily trend of occurrence during the hours of 1900 LT-0200 LT, with higher levels being localized within the hours of 2000-2300 LT. Generally, highest scintillation occurrences were recorded during the equinoxes, and the trend increased with solar activity. Specifically, scintillations were almost absent during June Solstices of the period under investigation, and it appears as if January is a non-scintillation month over equatorial Africa. On a scintillation active day, the number of satellites available to the receiver's view reduces as the duration of observation reduces. These results may support the development of future models that could provide real-time predictability of African equatorial scintillations, with a view to supporting the implementation of GNSS-based navigation in Africa.
Astronomy in the cultural heritage of African societies
(2006) Baki, Paul
The African perspectives of astronomy are explored from the point of view of using indigenous knowledge of the night sky for purposes of addressing local challenges such as food insecurity and periodic natural weather phenomena such as droughts and floods. The local ethnic groups use stellar positions, and plant and animal behaviour changes for purposes of forecasting the weather and climate for the coming seasons. These traditional indicators give rise to an interdisciplinary discourse that could benefit the community in environmental protection measures and boost the tourism industry in some countries in Africa
eGY-Africa: addressing the digital divide for science in Africa
(2013) Baki, Paul; Nguno, Anna; Barton, Charles; Amaeshi, Larry; Tenthani, Chifundo; Petitdidier, Monique; Cottrell, Les
Adoption of information and communication technologies and access to the Internet is expanding in Africa, but because of the rapid growth elsewhere, a Digital Divide between Africa and the rest of the world exists. In many sub-Saharan African countries, education and research sector suffers some of the worst deficiencies in access to the Internet, despite progress in the development of NRENs - National Research and Education (cyber) Networks. By contrast, it is widely acknowledged in policy statements from the African Union, the UN, and others that strength in this very sector provides the key to meeting and sustaining Millennium Development Goals. Developed countries with effective cyber-capabilities proclaim the benefits to rich and poor alike arising from the Information Revolution. This is still a dream for many scientists in African institutions. As the world of science becomes increasingly Internet-dependent, so they become increasingly isolated. eGY-Africa is a bottom-up initiative by African scientists and their collaborators to try to reduce this digital divide by a campaign of advocacy for better institutional facilities. Four approaches are being taken. The present status of Internet services, problems, and plans are being mapped via a combination of direct measurement of Internet performance (the PingER Project) and a questionnaire-based survey. Information is being gathered on policy statements and initiatives aimed at reducing the digital divide, which can be used for arguing the case for better Internet facilities. Groups of concerned scientists are being formed at the national, regional levels in Africa, building on existing networks as much as possible. Opinion in the international science community is being mobilized. Finally, and perhaps most important of all, eGY-Africa is seeking to engage with the many other programs, initiatives, and bodies that share the goal of reducing the digital divide - either as a direct policy objective, or indirectly as a means to an end, such as the development of an indigenous capability in science and technology for national development. The expectation is that informed opinion from the scientific community at the institutional, national, and international levels can be used to influence the decision makers and donors who are in a position to deliver better Internet capabilities. eGYAfrica workshops have been held approximately bi annually, the last of which was in Nairobi Kenya.
Features of the Night-Time F-Region Currents Over Equatorial Africa (August, 2001)
(2014) Adero, Awuor Ochieng; Baki, Paul; Kotze, Peter; Mito, Collins
In this paper, we present the features of the equatorial F-region current systems over equatorial Africa during nighttime on 05thAugust, 2001 observed at midnight. The observations have inferred from in situ CHAMP satellite measurements of the vector magnetic field. The magnitudes of the current along all the three magnetic field components of the Earth’s magnetic field varied considerably. The Bx-component recorded a diamagnetic effect of about 8nT, By-component recorded a current density of 5mA/m, and Bz-component reached a value of 3mA/m. The F-region dynamo, gravity dynamo and plasmapressure gradients are the possible mechanisms for the occurrence of these currents. The signatures confined to the equatorial region bounded by the Appleton anomaly.
Identification of Night-Time F- Region Currents from CHAMP Satellite Observations over Equatorial Africa
(2013) Ochieng, Adero Awuor; Baki, Paul; Kotze, Peter; Mito, Collins
The F-region currents are generally weak and difficult to detect. However, their contributions to the earth’s magnetic field variations are significant and cannot be ignored by the field modelers. CHAMP satellite has therefore provided a perfect opportunity to investigate the in-situ F-region currents on the night side of the equatorial region. The magnitudes of the current along all the three components of the earth’s magnetic field (X, Y, Z) are investigated. However in this paper, we present only the results on the Y-component where interesting magnetic residuals were observed. The X and Z-components were rather masked in much noise and would require further filtering. The currents appear in both the pre-midnight and postmidnight sectors and are spatially confined to the equatorial region bounded by the Appleton anomaly. The magnetic residuals are generally observed in the northern hemisphere of an order of 0.8nT, which gives a height-integrated current density of about 1.3mA/m.
The inverse problem of acoustic wave scattering by an air-saturated poroelastic cylinder
(2013) Ogam, Erick; Fellah, ZEA; Baki, Paul
The efficient use of plastic foams in a diverse range of structural applications like in noise reduction, cushioning, and sleeping mattresses requires detailed characterization of their permeability and deformation (load-bearing) behavior. The elastic moduli and airflow resistance properties of foams are often measured using two separate techniques, one employing mechanical vibration methods and the other, flow rates of fluids based on fluid mechanics technology, respectively. A multi-parameter inverse acoustic scattering problem to recover airflow resistivity (AR) and mechanical properties of an air-saturated foam cylinder is solved. A wave-fluid saturated poroelastic structure interaction model based on the modified Biot theory and plane-wave decomposition using orthogonal cylindrical functions is employed to solve the inverse problem. The solutions to the inverse problem are obtained by constructing the objective functional given by the total square of the difference between predictions from the model and scattered acoustic field data acquired in an anechoic chamber. The value of the recovered AR is in good agreement with that of a slab sample cut from the cylinder and characterized using a method employing low frequency transmitted and reflected acoustic waves in a long waveguide developed by Fellah et al. [Rev. Sci. Instrum. 78(11), 114902 (2007)].
Kenyan women in physics: Overcoming cultural, economic, and professional challenges
(2011) Baki, Paul; Kasina, Angeline; Nyamwandha, Cecilia; Kawira, Millien; Mburu, Jane; King'ori, Gladys; Kahonge, Teresia; Gichana, Zubeda
Efforts to attract, retain, and improve the status of girls and women in Kenya to the sciences, in particular physics, are outlined. Areas in which positive change has been observed are noted. Issues that still need to be addressed to realize the full potential of women undertaking physics are discussed.
A Study of the Equatorial Ionosphere Over Nairobi During Selected Magnetically Disturbed and Quiet Times for the Year 2009 Using Co-Located Instruments
(2014) Omondi, George; Ndinya, Boniface; Baki, Paul
Investigation of the behavior of the Equatorial Ionosphere over Nairobi-Kenya within the East Africa region is done using co-located instruments, that is, SCINDA-GPS system and a Magnetometer ( MAGDAS). This was done for magnetically disturbed days, 22 and 23 July,2009, as well as for quiet days before and after the geomagnetic disturbances. TEC depletions were observed and amplitude Scintillation indices plots were made and an attempt made to correlate these with modelled surface electric fields computed from magnetic field variations. The results show that most geoelectric field enhancements occured between 0700 LT and 1300 LT mostly in the east-west component and in the post-midnight local time while scintillations and TEC enhancements and depletions occurred mostly between 0900 LT and 1100 LT during geomagnetic disturbances and between 1300 LT and 1400 LT during quiet times.This may be attributed to the development of the Equatorial Ionization Anomaly or an extension of of the neutral wind dynamo driven by the E-region neutral wind and gravity waves generated by convection. Moreover, geoelectric field enhancements were accompanied by scintillations and TEC enhancements or depletions since pre-reversal enhancement in drift controls the occurence of scintillations.
A study on the response of the Equatorial Ionization Anomaly over the East Africa sector during the geomagnetic storm of November 13, 2012
(Elsevier, 2015) Olwendo, Ouko Joseph; Yosuke, Yamazak; Cilliers, Pierre; Baki, Paul; Ngwira, Chigomezyo M; Mito, Collins
Using a set of up to 12 International GNSS Services (IGS) receivers around the East African region, we present the formation of the peak of ionospheric Equatorial Ionization Anomaly during the geomagnetic storm of 13th November 2012. The diurnal pattern of total electron content (TEC) shows a strong negative storm during the main phase of the storm. Latitudinal variation of TEC shows development of strong Equatorial Ionization Anomaly (EIA) on the recovery phase. Evidence in terms of magnetic variations during the storm period, indicates that the penetration of interplanetary electric fields is the main cause of the negative ionospheric effect during the main phase of the storm. Observation shows the occurrence of very strong westward electric fields arising from the IMF Bz turning southward a few hours after sunset local time. TEC enhancement during the recovery phase on the 16th are attributed to the increased ionospheric disturbance dynamo electric fields. In addition the EIA crest was found to intensify in amplitude as well as expand in latitudinal extent.