This study examines the occurrences rate of geomagnetic storms during the solar cycles (SCs) 20-24. It also investigates the solar sources at SCs 23 and 24. The Disturbed storm time (Dst) and Sunspot Number (SSN) data were used in the study. The study establishes that the magnitude of the rate of occurrences of geomagnetic storms is higher (lower) at the descending phases (minimum phases) of solar cycle. It as well reveals that severe and extreme geomagnetic storms (Dst <-250 nT) seldom occur at low solar activity but at very high solar activity and are mostly associated with coronal mass ejections (CMEs) when occurred. Storms caused by CME + CH-HSSW are more prominent during the descending phase than any other phase of the solar cycle. Solar minimum features more CH-HSSW- asso-ciated storms than any other phase. It was also revealed that all high intensity geomagnetic storms (strong, severe and extreme) are mostly associated with CMEs. However, CH-HSSW can occasionally generate strong storms during solar minimum. The results have proven that CMEs are the leading cause of geomagnetic storms at the ascending, maximum and the descending phases of the cycles 23 and 24 followed by CME + CH-HSSW. The results from this study indicate that the rate of occurrence of geomagnetic storms could be predicted in SC phases. (c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Broadband access drives the global digital economy and has triggered the emergence of newer radio access technologies to meet data-driven consumers' expectations. In the period 2019-2025, it is estimated that the Compound Annual Growth Rate (CARG) of Sub-Sahara Africa will be above 28 % though ranked lowest amongst other regions. The Covid-19 pandemic has occasioned an unprecedented global demand for broadband internet access. Nigeria's broadband access is 42.02 %, which needs an advanced radio communication network infrastructure upgrade in order to bridge the current gap. Consequently, satellite-cellular convergence is a game-changer for increased rural and urban broadband connectivity penetration. The emergence of the fifth-generation (5G) network is expected to break new market share grounds and increase internet penetration. This paper focuses on the frequency range 1 (FR1: 450 – 7125 MHz) band due to their advantages, including broader coverage, better capacity, and low-cost deployment in sub-Saharan Africa. This paper presents the current usage of Nigeria spectrum bands allocated for mobile communication in the sub-7 GHz band. Potential spectrum bands such as 450-470 MHz, 1427-1518 MHz, 2300-2400 MHz, 3600-4200 MHz, 4400-5000 MHz, 5480-5710 MHz 5900-7125 MHz are suggested to add to the already recommended bands due to their low utilization (i.e., below 10 % average duty cycle). In addition, it is suggested to deploy carrier aggregation methodology to meet gigabit speed for 5G in Nigeria. Copyright © 2022 Praise Worthy Prize S.r.l.-All rights reserved. © 2022 Praise Worthy Prize S.r.l. All rights reserved

We performed a diagnostic study of geomagnetic storm-induced disturbances that are coupled to the mid-latitude D region by quantifying the propagation characteristics of very low-frequency (VLF) radio signals from transmitters located in Cumbria, UK (call sign GQD), and Rhauderfehn, Germany (DHO), and received in southern France (A118). We characterised the diurnal VLF amplitudes from two propagation paths into five metrics, namely the mean amplitude before sunrise (MBSR), the midday amplitude peak (MDP), the mean amplitude after sunset (MASS), the sunrise terminator (SRT) and the sunset terminator (SST). We analysed and monitored trends in the variation of signal metrics for up to 20 storms to relate the deviations in the signal amplitudes that were attributable to the storms. Five storms and their effects on the signals were examined in further detail. Our results indicate that relative to pre-storm levels the storm day MDP exhibited characteristic decreases in about 80 % (67 %) of the events for the DHO-A118 (GQD-A118) propagation path. The MBSR showed decreases of about 60 % (77 %), whereas the MASS decreased by 67 % (58 %). Conversely, the SRT and SST showed amplitude decreases of 33 % (25 %) and 47 % (42 %), respectively. Of the two propagation paths, the amplitude decreases for the DHO-A118 propagation path signal were greater, as previously noted by Nwankwo et al. (2016). To better understand the state of the ionosphere over the signal propagation paths and how it might have affected the VLF amplitudes, we further analysed the virtual heights (h'E, h'F1 and h'F2) and critical frequencies (foE, foF1 and foF2) from ionosondes located near the transmitters. The results of this analysis showed significant increases and fluctuations in both the F-region critical frequencies and virtual heights during the geomagnetic storms. The largest increases in the virtual heights occurred near the DHO transmitter in Rhauderfehn (Germany), suggesting a strong storm response over the region which might account for the larger MDP decrease along the DHO-A118 propagation path.

This paper presents a design of a centre-fed Rectangular Microstrip Patch Antenna (RMSA) that resonates at exactly 3.8 GHz. The effect of the dielectric material’s choice, substrate height, dielectric constant, and the substrate material is on the RMSA for a constant resonant frequency while maintaining signal integrity and reducing signal loss. The antenna’s gain and input return loss are improved by adjusting the upper and lower bounds of the height of the dielectric substrate. Results show that a maximum bandwidth of 350 MHz, a gain of 7.77 dBi, and input return loss (S11) of below–33 dB were obtained. Furthermore, a smaller dielectric constant below 2.5 and a Voltage Standing Wave Ratio (VSWR) below 2 dB will conveniently provide a wider bandwidth (BW) of over 250 MHz which is convenient to meet frequency range 1 (FR1) bandwidth expectation.

Research on longitudinal discrepancies in local ionospheric variability, especially in equatorial and low-latitude regions, is a focal point of interest for the space weather modeling community. The ionosphere over these regions is influenced by complex electrodynamics, wind, and temperature dynamics that can seriously impact dynamic technological systems such as satellite tracking and positioning, satellite radio communication, and navigation control systems. Here, we researched the longitudinal variability in the ionospheric total electron content (TEC) by analyzing observed global positioning system (GPS)-derived TEC values along with those extracted from the most reliable global ionospheric maps (GIMs) and the International Reference Ionosphere (IRI-2016) model at selected stations in the vicinity of the magnetic equator along the American, African, and Asian longitude sectors. The period of study covered the descending (2016–2017) and deep solar minimum (2018–2019) years in the 24th solar cycle. Apart from the decreasing trend of the TEC from the descending to deep solar minimum period irrespective of season and longitude sector, the results showed a relatively higher magnitude of TEC in the African longitude than the other two longitude sectors. Despite evident overestimation and underestimations of TEC in both models, GIM predictions generally looked better in terms of observed variation patterns, especially in the African longitude. The study also highlights the seasonal and semiannual effects of longitudinal variations in TEC, manifesting in local time offsets and some peculiar anomalies, which seemed to be different from previously reported results, especially during the solar minimum years at the three longitude sectors. The insignificant effects of longitudinal variations on the equinoctial asymmetry are attributed to the diverse electron density distribution and ionospheric morphology at the three longitude sectors that will prompt further investigations in the future. The outcomes from this study may augment the past efforts of scientists to understand the seasonal effects of the longitudinal variations in TEC, thereby complementing the improvements of ionospheric representations in global ionosphere models and maps.

This paper examines the accuracy of the Global Positioning System (GPS) within the African low-latitude sector. We evaluated the vertical and horizontal of the single-point positioning (SPP) accuracy of GPS and critically analysed the effects of the equatorial ionospheric anomaly (EIA) over the region of study. Our results imply that using single-frequency GPS for any application could give a positioning error up to 45.00 m vertically and similar to 25.00 m horizontally. The study revealed that 54% of GNSS positioning errors during the night-time could be linked to ionospheric plasma irregularities. Also, positioning errors are higher in western Africa than in the eastern region. The influence of geomagnetic activities is not consistent with GPS positioning accuracy. However, positioning errors are lower during geomagnetically disturbed conditions in comparison to quiet conditions. The unique phenomena of the EIA can severely limit GPS services at night-time for positioning in the study area.

The ionosphere model is essential to satellite-based systems to accurately correct the ionospheric error encountered by satellite signals en route. The Levenberg–Marquardt backpropagation (LMBP) algorithm in the artificial neural network (ANN) was used in this work to predict the total electron content (TEC) within the trough of equatorial ionization anomaly (EIA) over Nigeria. Two sets of data were used over the period of three consecutive years (2011–2013) of high solar activity. The first set was used as an input to the ANN model and the second set of data was used as a target. Seventy percent of the data sets were used to train the network, 15% of the data were used for validation, and 15% used for testing. The performance of the model was assessed during specific quiet and disturbed geomagnetic conditions. The regression analysis of the model output was optimized by minimizing a cost function of the mean square error (MSE). The results of the errors, regression, and comparative analyses have revealed that the ANN model is able to predict accurate and reliable TEC that compares well with the actual experimental data at any geophysical conditions. Hence, this model would be useful to forecast TEC over Nigeria to a reliable threshold.

We analysed variations in signal metrics and the diurnal amplitude of VLF radiowaves from four propagation paths during intervals of 4 geomagnetic storms on 17, 26 September, 25 October and 1 Novem...

Energetic charged particle precipitation associated with solar wind perturbations causes enhanced high-frequency radiowave absorption in the high-latitude ionosphere. This study models 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjarvi, Finland obtained during solar cycle 23 (1996-2009) associated with the passage of interplanetary coronal mass ejections (ICMEs) past Earth; ICMEs are a major driver of enhanced geomagnetic activity. Superposed epoch analysis suggests that the r6absorption vs. time profile depends on whether ICME arrival occurs in the day-time (10-14 MLT) or night-time (22-02 MLT) for IRIS, with peak absorption occurring similar to 2-3 h ahead of ICME arrival or similar to 4 h after ICME arrival, respectively. We determine which combinations of solar wind and IMF parameters show the best correlation with the absorption associated with day-time or night-time arriving ICMEs using superposed epoch analysis and the least squares estimation method. Various combinations of solar wind parameters (including bulk velocity v, density n, and the interplanetary magnetic field north and south components Bz and the SYMH geomagnetic index), have been ranked to obtain the best coupling function for the absorption associated with day- and night-time arriving ICMEs. The absorption for day-time events is found to correlate closely with the solar wind dynamic pressure, SYMH, and the northward direction of the Bz while the absorption for night-time events is most closely related to the direction of the Bz and SYMH. The coupling functions are found to model the observed absorption successfully, with correlation coefficients of similar to 0.7-0.8 between the observed and modelled absorption.

Ionosphere plays crucial role in satellite communication as well as the modern space-based positioning, navigation and timing appli-cations. Progressive exploitation of ground and space-based observations across the African region has relatively strengthened the under -standing and modeling of spatiotemporal ionospheric variations over the territory. However, it is also equally important to understand the latitudinal behaviour of ionosphere over the African longitude that would reinforce the ionospheric delay error modelling practices for an improved radio communication along the satellite pass. Hence, the aim of this research is to investigate the diurnal, seasonal and latitudinal variations of global positioning system derived total electron content (GPS-TEC) and to assess the performance of the recent version of empirical international reference ionosphere (IRI-2016) and plasmaspheric IRI (IRI-PLAS 2017) models during the ascending phase of solar cycle 24 (2012). The study is also supported by the integrated ionospheric TEC (IONO-TEC) extracted from the Digisonde observations in the vicinity of GPS receiver locations. The 3 GPS stations considered in this study are at a) an equatorial/ low-latitude location Federal University of Technology, Yola (FUTY; 9.35 degrees N, 12.50 degrees E, 4.91 degrees S dip), b) a mid-latitude location Ankara (ANKR; 39.89 degrees N, 32.76 degrees E, 57.62 degrees N dip), and a high-latitude location Tromso (TRO1; 69.66 degrees N, 18.94 degrees E, 78.17 degrees N dip) in the northern hemi-sphere. Observations show the magnitude of TEC generally decreases with increasing latitude. While the average diurnal maximum of GPS-TEC at equatorial and low-latitude follow an almost equal level of magnitude during March and September equinoxes, the observations at middle and high latitude stations presents the highest magnitudes during the September equinox. Moreover, we noticed obvious higher magnitude of GPS-TEC than IONO-TEC at the three stations suggesting the discrepancies could be corresponding to the topside modeling and plasmaspheric contributions. The other prominent feature is the pattern of diurnal TEC being dome shaped at middle and high latitude locations whereas the equatorial and low latitude location manifested a noon bite-out characteristic in the IONO-TEC, IRI-2016, and IRI-PLAS outcomes. The comparative analysis of IRI-2016 and IRI-PLAS 2017 estimated TEC with the GPS-TEC show a clear overestimation of IRI-PLAS 2017 outcomes irrespective of seasons and latitudinal locations whereas the IRI2016 outcomes either overestimated or underestimated the GPS-TEC. Hence, this study reveals that IRI-2016 performs better predictions compared to IRI-PLAS 2017 at all the three latitudinal locations. Such a latitudinal comparison across the African-European longitudinal sector may complement towards the efforts for improving the regional as well as global ionospheric model performances. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved.

The ionosphere is the major error source for the signals of global positioning system (GPS) satellites. In the analysis of GPS measurements, ionospheric error is assumed to be somewhat of a nuisance. The error induced by the ionosphere is proportional to the number of electrons along the line of sight (LOS) from the satellite to receiver and can be determined in order to study the diurnal, seasonal, solar cycle and spatial variations in the ionosphere during quiet and disturbed conditions. In this study, we characterize the diurnal, seasonal and solar cycle variation in observed total electron content (OBS-TEC) and compare the results with the International Reference Ionosphere (IRI-2016) model. We obtained TEC from a dual-frequency GPS receiver located at Birnin Kebbi Federal Polytechnic (BKFP) in northern Nigeria (geographic location: 12.64∘ N, 4.22∘ E; 2.68∘ N dip) for the period 2011–2014. We observed differences between the diurnal variation in OBS-TEC and the IRI-2016 model for all hours of the day except during the post-midnight hours. Slight post-noon peaks in the daytime maximum and post-sunset decrease and enhancement are observed in the diurnal variation in OBS-TEC during the equinoxes. On a seasonal scale, we observed that OBS-TEC values were higher in the equinoxes than the solstices only in 2012. However, in 2011, the September equinox and December solstice recorded a higher magnitude, followed by the March equinox, and the magnitude was lowest in the June solstice. In 2013, the December solstice magnitude was highest, followed by the equinoxes, and it was lowest in the June solstice. In 2014, the March equinox and December solstice magnitudes were higher than the September equinox and June solstice magnitude. The June solstice consistently recorded the lowest values for all the years. OBS-TEC is found to increase from 2011 to 2014, thus revealing solar cycle dependence.

Solar flare events are a major observing emphasis for space weather because they affect the ionosphere and can eject high-energy particles that can adversely affect Earth's technologies. In this study we model 38.2 MHz cosmic noise absorption (CNA) by utilising measurements from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi, Finland obtained during solar cycle 23 (1996–2009). We utilised X-ray archive for the same period from the Geostationary Operational Environmental Satellite (GOES) to study solar flare induced cosmic noise absorption. We identified the threshold of flare (M4 class) that could bear significant influence on CNA. Through epoch analysis, we show the magnitude of absorption that each class of flare could produce. Using the parameters of flare and absorption we present a model that could provide the basis for nowcast of CNA induced by M and X-class solar flares.

Abstract. Satellite radio signals are affected by the presence of electrons in the earth’s upper atmosphere (ionosphere). The more electrons in the path of the satellite radio signals, the more the impact on the accuracy of satellite navigation systems such as the Global Positioning System (GPS)/ Global Navigation Satellite System (GNSS) and GLONASS. These electrons introduce several meters of error in position calculation. Total Electron Content (TEC) is used to monitor possible space weather impacts on satellite to ground communication and satellite navigation. TEC is modified in the ionosphere by changing solar Extreme Ultra-Violet (EUV) radiation, geomagnetic storms, and the atmospheric waves that propagate up from the lower atmosphere. Therefore, TEC depends on local time, latitude, longitude, season, geomagnetic conditions, solar cycle activity, and condition of the troposphere. A dual frequency GPS receiver located at an equatorial station, Birnin-Kebbi in Northern Nigeria (geographic location: 12.64° N; 4.22° E), has been used to investigate variation of TEC during the period of 2011 to 2014. We investigate the diurnal, seasonal and solar cycle dependence of GPS-TEC. The result shows that TEC increases from a minimum at 0400 local time (LT) to maximum daytime peak between 1300–1600 LT and then decreases to a minimum value after sunset for all the years. Slight post-noon peaks in the daytime maximum and post-sunset decrease and enhancement is observed in some months. We observed that TEC were higher in the equinoxes than the solstices only in 2012. Where as in 2011, September equinox and December solstice recorded higher magnitude followed by March equinox and lowest in June solstice. In 2013, December solstice magnitude was highest, followed by the equinoxes and lowest in June solstice. In 2014, March equinox and December solstice magnitude were higher than September equinox and June solstice magnitude. June solstice consistently recorded the lowest values for all the years.

As climate change could affect energy production, it can also undermine telecommunications development which requires increased energy consumption to drive improvement in network penetration, coverage and capacity. Employing secondary data analysis and simulation, this paper presents a study on climate change effect on energy consumption of telecommunication base stations. The impact of climate change on energy consumption was examined by introducing a climate factor,, into validated Base Transceivers Stations (BTS) power consumption models. The BTS energy demand was found to increase with increase in temperature due to cooling requirement. The result shows that, with 1oC increase in outdoor temperature, heat flow through BTS shelter increases by 6.25%. This increase effect, manifests on cooling system with above 1 kW power. The result presented shows the importance of taking climate change variables into consideration when planning next generation cellular networks for sustainable deployment.Key Words: Climate change, renewable energy, cellular systems, base stations, mmWave communication, sustainability

During the geomagnetic disturbances, the geomagnetically induced current (GIC) are influenced by the geoelectric field flowing in conductive Earth. In this paper, we studied the variability of GICs, the time derivatives of the geomagnetic field (dB/dt), geomagnetic indices: Symmetric disturbance field in H (SYM-H) index, AU (eastward electrojet) and AL (westward electrojet) indices, Interplanetary parameters such as solar wind speed (v), and interplanetary magnetic field (Bz) during the geomagnetic storms on 31 March 2001, 21 October 2001, 6 November 2001, 29 October 2003, 31 October 2003 and 9 November 2004 with high solar wind speed due to a coronal mass ejection. Wavelet spectrum based approach was employed to analyze the GIC time series in a sequence of time scales of one to twenty four hours. It was observed that there are more concentration of power between the 14–24h on 31 March 2001, 17–24h on 21 October 2001, 1–7h on 6 November 2001, two peaks were observed between 5–8h and 21–24h on 29 October 2003, 1–3h on 31 October 2003 and 18–22h on 9 November 2004. Bootstrap method was used to obtain regression correlations between the time derivative of the geomagnetic field (dB/dt) and the observed values of the geomagnetic induced current on 31 March 2001, 21 October 2001, 6 November 2001, 29 October 2003, 31 October 2003 and 9 November 2004 which shows a distributed cluster of correlation coefficients at around r=−0.567, −0.717, −0.477, −0.419, −0.210 and r=−0.488 respectively. We observed that high energy wavelet coefficient correlated well with bootstrap correlation, while low energy wavelet coefficient gives low bootstrap correlation. It was noticed that the geomagnetic storm has a influence on GIC and geomagnetic field derivatives (dB/dt). This might be ascribed to the coronal mass ejection with solar wind due to particle acceleration processes in the solar atmosphere.

We have used chains of Magnetic Data Acquisition System (MAGDAS) magnetometer records of the horizontal (H) and vertical (Z) magnetic field intensities during September 2008 to August 2009 (year of deep minimum) across Africa to study their variability during the quietest international days, which coincidently associated with the sudden stratospheric warming (SSW) event in January 2009. This selection of the most international quiet days is indicative of 80% that are strongly associated with days when unusually strong and prolonged sudden SSW event occurs in January 2009. Interestingly, in January, a significant magnitude depletion of solar quiet (S-q) equivalent current was observed near noon hours around the magnetic equator (Addis Ababa, ABB) compared to any other months along with a consistent significantly reduced value across the Northern Hemisphere and moderate decrease at the Southern Hemisphere. Also, we found that Nairobi and Dar es Salaam at the Southern Hemisphere, which are close to ABB (dip equator), are strongly prone to westward electric field compared to the magnetic equator and Khartoum at the Northern Hemisphere. Significant negative values of MSq(Z) magnitudes observed near noon hours at Hermanus indicate the presence of induced currents that suggest ocean effects along with reversal to significant positive values in the afternoon, which subsided before 1800 LT in almost all the months, indicate stronger influence of ionospheric currents. On seasonal variability of S-q(H), a slight depression at ABB during September equinox is one of the evidences of seasonal S-q focus shift. Latitudinal variability of Sq near-noon hours was also investigated.

The amplitude and phase of VLF/LF radio signals are sensitive to changes in electrical conductivity of the lower ionosphere which imprints its signature on the Earth–ionosphere waveguide. This characteristic makes it useful in studying sudden ionospheric disturbances, especially those related to prompt X-ray flux output from solar flares and gamma ray bursts (GRBs). However, strong geomagnetic disturbance and storm conditions are known to produce large and global ionospheric disturbances, which can significantly affect VLF radio propagation in the D region of the ionosphere. In this paper, using the data of three propagation paths at mid-latitudes (40–54°), we analyse the trend in variation of aspects of VLF diurnal signal under varying solar and geomagnetic space environmental conditions in order to identify possible geomagnetic footprints on the D region characteristics. We found that the trend of variations generally reflected the prevailing space weather conditions in various time scales. In particular, the 'dipping' of mid-day signal amplitude peak (MDP) occurs after significant geomagnetic perturbed or storm conditions in the time scale of 1–2 days. The mean signal amplitude before sunrise (MBSR) and mean signal amplitude after sunset (MASS) also exhibit storm-induced dipping, but they appear to be influenced by event's exact occurrence time and the highly variable conditions of dusk-to-dawn ionosphere. We also observed few cases of the signals rise (e.g., MDP, MBSR or MASS) following a significant geomagnetic event. This effect may be related to storms associated phenomena or effects arising from sources other than solar origin. The magnitude of induced dipping (or rise) significantly depends on the intensity and duration of event(s), as well as the propagation path of the signal. The post-storm day signal (following a main event, with lesser or significantly reduced geomagnetic activity) exhibited a tendency of recovery to pre-storm day level. In the present analysis, we do not see a well-defined trend in the variation of the post-storm sunrise amplitude terminator (SRT) and sunset terminator (SST). The SRT and SST signals show more dipping in GQD-A118 propagation path but generally an increase along DHO-A118 propagation path. Thus the result could be propagation path dependent and detailed modelling is required to understand these phenomena.