Browsing by Author "Amabayo, Emirant Bertillas"

Now showing 1 - 7 of 7
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    Climatology of ionospheric scintillations and TEC trend over the Ugandan region
    (Advances in Space Research, 2014) Amabayo, Emirant Bertillas; Jurua, Edward; Cilliers, Pierre J.; Habarulema, John Bosco
    This study presents results on the investigation of the diurnal, monthly and seasonal variability of Total Electron Content (TEC), phase (rU) and amplitude (S4) scintillation indices over Ugandan (Low latitude) region. Scintillation Network Decision Aid (SCINDA) data was obtained from Makerere (0.34 N, 32.57 E) station, Uganda for two years (2011 and 2012). Data from two dual frequency GPS receivers at Mbarara (0.60 S, 30.74 E) and Entebbe (0.04 N, 32.44 E) was used to study TEC climatology during the same period of scintillation study. The results show that peak TEC values were recorded during the months of October–November, and the lowest values during the months of July–August. The diurnal peak of TEC occurs between 10:00 and 14:00 UT hours. Seasonally, the ascending and descending phases of TEC were observed during the equinoxes (March and September) and solstice (June and December), respectively. The scintillations observed during the study were classified as weak (0.1 S4,rU 0.3) and strong (0.3
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    Concentrations and human health risk assessment of selected heavy metals in soils and food crops around Osukuru phosphate mine, Tororo District, Uganda
    (Toxicology Reports, 2022) Tagumira, Abudallah; Biira, Saphina; Amabayo, Emirant Bertillas
    This study investigated the concentrations of heavy metals, particularly chromium (Cr), cadmium (Cd); lead (Pb), copper (Cu), and iron (Fe) in the soil and crops. The accumulation of heavy metals in the crop system, the probable daily intake of heavy metals, and the assessment of potential health threats associated with the uptake of metals by the residents around the Osukuru phosphate mine in Tororo, Uganda. The concentrations were assessed with the assistance of an Atomic Absorption Spectrometer (AAS). The crops studied were amaranthus (Amaranthus hybridus) leaves, pumpkin (Cucurbita pepo) leaves, maize (Zea mays) grains, and cowpeas (Vigna unguiculata) leaves. A total of 200 samples were collected from five villages of Osukuru Sub County. The findings of this study showed that elemental concentrations of heavy metals in the soil were within the standard recognized limit for agriculture as documented by World Health Organization (WHO) and European Union (EU). While more noticeable levels of these elements were detected in crop samples, especially amaranthus. Chromium composition was lower than the detection level in all samples. The transfer factor results showed elemental intake by the crops in the sequence; Fe > Cu > Cd > Pb. The probable daily intakes of the elements were below the daily threshold values endorsed by WHO/FAO. The health threat index showed high values for Pb and Cd from maize but low values of Cu and Fe in all samples and therefore these crops may not be very safe for human intake.
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    Instantaneous Ionospheric Scintillation Mapping over the East African Region by use of GPS Derived Amplitude Scintillation Proxy
    (Asian Journal of Research and Reviews in Physics, 2021) Amabayo, Emirant Bertillas; Andima, Geoffrey; Ssenyunzi, Richard Cliffe
    Ionospheric scintillation activity over the East African region is often monitored using measurements from the SCIntillation Network Decision Aid (SCINDA) receivers. Many of the SCINDA receivers over East Africa are currently not archiving data and therefore a large part of the region remain un sampled. We investigated the possibility to use dual frequency receivers of the Global Navigation Satellite System (GNSS) network for scintillation mapping. A proxy for amplitude scintillation was first derived by scaling the rate of change of total electron content index (ROTI). The proxy was validated against S4 derived from nearly collocated SCINDA receivers over the region. A good correlation was observed between the proxy and S4. The proxy was then used to map the occurrence of amplitude scintillation over East Africa based on semivariogram modeling and Kriging interpolation technique. The results indicate that the S4 values had a good positive correlation with the simulated S4p from the Kriging interpolation. This observation suggests that data from the dual frequency receivers of GNSS may be used to map scintillation over East Africa. These maps can in turn be used to study the evolution of ionospheric scintillation patterns over the region.
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    Multi-station observation of ionospheric irregularities over South Africa during strong geomagnetic storms
    (Advances in Space Research, 2013) Amabayo, Emirant Bertillas; Pierre, J. Cilliers
    This paper presents results pertaining to the response of the mid-latitude ionosphere to strong geomagnetic storms that occurred from 31 March to 02 April 2001 and 07–09 September 2002. The results are based on (i) Global Positioning Systems (GPSs) derived total electron content (TEC) variations accompanying the storm, (ii) ionosonde measurements of the ionospheric electrodynamic response towards the storms and (iii) effect of storm induced travelling ionospheric disturbances (TIDs) on GPS derived TEC. Ionospheric data comprising of ionospheric TEC obtained from GPS measurements, ionograms, solar wind data obtained from Advanced Composition Explorer (ACE) and magnetic data from ground based magnetometers were used in this study. Storm induced features in vertical TEC (VTEC) have been obtained and compared with the mean VTEC of quiet days. The response of the mid-latitude ionosphere during the two storm periods examined may be characterised in terms of increased or decreased level of VTEC, wave-like structures in VTEC perturbation and sudden enhancement in hmF2 and h0F. The study reveals both positive and negative ionospheric storm effects on the ionosphere over South Africa during the two strong storm conditions. These ionospheric features have been mainly attributed to the travelling ionospheric disturbances (TIDs) as the driving mechanism for the irregularities causing the perturbations observed. TEC perturbations due to the irregularities encountered by the satellites were observed on satellites with pseudo random numbers (PRNs) 15, 17, 18 and 23 between 17:00 and 23:00 UT on 07 September 2002.
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    Statistical analysis of TEC perturbations over a low latitude region during 2009–2013 ascending solar activity phase
    (Advances in Space Research, 2015) Andima, Geoffrey; Jurua, Edward; Amabayo, Emirant Bertillas; Habarulema, John Bosco
    Total Electron Content (TEC) perturbations are manifestations of ionospheric irregularities which induce fluctuations in the amplitude and phase of trans-ionospheric radio signals. TEC data derived from Global Positioning System (GPS) receivers at Mbarara (Geogra. 0.60 N, 30.74 E and Geomag. 10.22 N, 102.36 E) and Entebbe (Geogra. 0.04 N, 32.44 E and Geomag. 9.53 N, 104.10 E) from 2009 to 2013 were used to study TEC perturbations over the low latitude region of Uganda. The results show that the frequency of occurrence of TEC perturbations of >4 TECU increased steadily from 2009 to 2013. TEC perturbations with amplitude <4 TECU occurred at all times. The likelihood of TEC perturbations exceeding 6 TECU was higher during the equinoxes than during the solstices in most of the years. Comparison of TEC perturbations with 10.7 cm solar radio flux (F10.7) data showed a weak positive correlation with this solar proxy. Wavelet analysis performed on the TEC perturbations revealed wave-like oscillations with periods typical of Traveling Ionospheric Disturbances (TID). These wave-like structures (WLS) dominated from 13:00 to 19:00 LT for most of the years analyzed.
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    Statistical characterisation of spread F over South Africa
    (2011) Amabayo, Emirant Bertillas; McKinnell, Lee-Anne; Cilliers, Pierre J.
    The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4 digisondes in 1996 and 2000 at Grahamstown (33.32 S, 26.50 E) and Madimbo (22.38 S, 30.88 E) respectively. This study is intended to quantify the probability of occurrence of F region disturbances associated with SF over South Africa. A study was conducted using data for 8 years (2001–2008) over Madimbo (with a time resolution of 30 min) and Grahamstown (with a variable time resolution of 15 and 30 min). In this study, SF has been classified into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The SF events were identified by manually identifying ionograms showing SF and tabulating them according to type for further statistical analysis. The results show that the diurnal pattern of SF peaks strongly between 01:00 and 02:00 local time, LT (LT = UT + 2 h), where UT is the universal time. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown in 2001 and 2005, except for RSF which had peaks during autumn and spring in 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing solar activity, with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during winter months at both Madimbo and Grahamstown. In this study, SF was evident in 0.03% and 0.06% of the available ionograms at Madimbo and Grahamstown respectively during the 8 years.
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    Tracking the Ionospheric Response to the Solar Eclipse of November 03, 2013
    (International Journal of Atmospheric Sciences, 2014) Amabayo, Emirant Bertillas; Anguma, Simon Katrini; Jurua, Edward
    The ionospheric dynamics is highly influenced by the solar radiation. During a solar eclipse, the moon occults the solar radiation fromreaching the ionosphere, whichmay drastically affect the variability of the ionosphere. The variability of total electron content (TEC) observed by dual frequency Global Positioning System (GPS) receivers has made it possible to study effects of solar eclipse on the ionosphere. Total eclipse occurred on November 03, 2013, and the maximum amplitude was visible at Owiny in northern Uganda. Ionospheric behavior during this eclipse was analysed by using TEC data archived at Mbarara (MBAR),Malindi (MAL2), Eldoret (MOIU), and Kigali University (NURK) International GPS Satellite (IGS) stations. TEC variations of four consecutive days were used to study instantaneous changes of TEC during the eclipse event. The results generally show TEC decrease at the four stations. However, a maximum perturbation amplitude of ≥20 TECU was observed at MAL2 (18:00–20:00UT) which is further south of the equator than the other stations. TEC enhancement and depletion were observed during the totality of the eclipse at MOIU,MBAR, NURK, and MAL2 (13:00–15:00UT). This study found out that the ionospheric TEC over East Africa was modified by wave-like energy and momentum transport and obscuration of the solar disc due to the total solar eclipse.