scholarly journals Variation in total electron content with sunspot number during the ascending and maximum phases of solar cycle 24 at Birnin Kebbi

2018 ◽  
Author(s):  
Aghogho Ogwala ◽  
Emmanuel Olufemi Somoye ◽  
Olugbenga Ogunmodimu ◽  
Rasaq Adewemimo Adeniji-Adele ◽  
Eugene Oghenakpobo Onori ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Total Electron Content ◽  
Local Time ◽  
Satellite Navigation ◽  
Electron Content ◽  
Total Electron ◽  
June Solstice ◽  
December Solstice ◽  
Radio Signals ◽  
The Impact

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.

scholarly journals Diurnal, seasonal and solar cycle variation of total electron content and comparison with the IRI-2016 model at Birnin Kebbi

2019 ◽  
Author(s):  
Aghogho Ogwala ◽  
Emmanuel Olufemi Somoye ◽  
Olugbenga Ogunmudimu ◽  
Rasaq Adewemimo Adeniji-Adele ◽  
Eugene Ogheneakpobor Onori ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Diurnal Variation ◽  
Total Electron Content ◽  
Electron Content ◽  
Total Electron ◽  
Equatorial Station ◽  
Solar Cycle Variation ◽  
June Solstice ◽  
December Solstice ◽  
Cycle Dependence

Abstract. Total Electron Content (TEC) is an important ionospheric parameter used to monitor possible space weather impacts on satellite to ground communication and satellite navigation system. 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 observed (OBS) TEC and comparison with latest version of International Reference Ionosphere (IRI-2016) model. On a general note, diurnal variation reveals discrepancies between OBS-TEC and 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 of OBS-TEC of some months. On a seasonal scale, we observed that OBS-TEC values 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. OBS-TEC is found to increase from 2011 to 2014, thus revealing solar cycle dependence.

scholarly journals Diurnal, seasonal and solar cycle variation in total electron content and comparison with IRI-2016 model at Birnin Kebbi

2019 ◽  
Vol 37 (5) ◽  
pp. 775-789 ◽  
Author(s):  
Aghogho Ogwala ◽  
Emmanuel Olufemi Somoye ◽  
Olugbenga Ogunmodimu ◽  
Rasaq Adewemimo Adeniji-Adele ◽  
Eugene Oghenakpobor Onori ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Diurnal Variation ◽  
Total Electron Content ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
June Solstice ◽  
December Solstice

Abstract. 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.

scholarly journals Studying the variability in the diurnal and seasonal variations in GPS total electron content over Nigeria

2017 ◽  
Vol 35 (3) ◽  
pp. 701-710 ◽  
Author(s):  
Victor Adetayo Eyelade ◽  
Adekola Olajide Adewale ◽  
Andrew Ovie Akala ◽  
Olawale Segun Bolaji ◽  
A. Babatunde Rabiu
Keyword(s):  
Seasonal Variation ◽  
Total Electron Content ◽  
Seasonal Variations ◽  
Gps Data ◽  
Electron Content ◽  
Total Electron ◽  
Gps Tec ◽  
June Solstice ◽  
December Solstice ◽  
Annual Distribution

Abstract. The study of diurnal and seasonal variations in total electron content (TEC) over Nigeria has been prompted by the recent increase in the number of GPS continuously operating reference stations (CORSs) across Nigeria as well as the reduced costs of microcomputing. The GPS data engaged in this study were recorded in the year 2012 at nine stations in Nigeria located between geomagnetic latitudes – 4.33 and 0.72° N. The GPS data were used to derive GPS TEC, which was analysed for diurnal and seasonal variations. The results obtained were used to produce local GPS TEC maps and bar charts. The derived GPS TEC across all the stations demonstrates consistent minimum diurnal variations during the pre-sunrise hours 04:00 to 06:00 LT, increases with sharp gradient during the sunrise period (∼ 07:00 to 09:00 LT), attains postnoon maximum at about 14:00 LT, and then falls to a minimum just before sunset. Generally, daytime variations are found to be greater than nighttime variations, which range between 0 and 5 TECU. The seasonal variation depicts a semi-annual distribution with higher values (∼ 25–30 TECU) around equinoxes and lower values (∼ 20–25 TECU) around solstices. The December Solstice magnitude is slightly higher than the June Solstice magnitude at all stations, while March Equinox magnitude is also slightly higher than September Equinox magnitude at all stations. Thus, the seasonal variation shows an asymmetry in equinoxes and solstices, with the month of October displaying the highest values of GPS TEC across the latitudes.

scholarly journals ANALYSES OF TOTAL ELECTRON CONTENT VARIATIONS OVER NORTHERN AND SOUTHERN NIGERIA

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Aghogho Ogwala
Keyword(s):  
Total Electron Content ◽  
Seasonal Variations ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Dual Frequency ◽  
The South ◽  
Total Electron ◽  
The North ◽  
December Solstice ◽  
Latitudinal Difference

Total electron content (TEC) is a parameter of the ionosphere that produces great effect on radio signals. We present the diurnal and seasonal variations of vertical total electron content (vTEC) during the ascending phase of solar cycle 24. A moderate solar activity year (2011) with sunspot number, Rz = 55.7 is used in this study. Total electron content (TEC) deduced from the dual frequency GPS measurements obtained at two ground stations namely: ABUZ (Zaria) with longitude 7.39oE in the north and UNEC (Enugu) with longitude 7.30oE in the south are considered. Both stations are located within the same longitude and has a latitudinal difference of 4.74o in the Nigerian equatorial ionosphere (NEI). Comparison of diurnal and seasonal variations of TEC is carried out for both stations. The diurnal variation of TEC shows a steep increase starting from sunrise, reaching daytime maximum between 13 – 15 LT at UNEC and 14 – 16 LT at ABUZ, then falls to a minimum at sunset. Dawn depression occurred at the same local time of 04 LT at both stations. On a seasonal scale, Pre- and post-midnight values were highest during the Equinoxes, followed by December solstice and least in June Solstice season at ABUZ. Pre- and post-midnight values were also higher during the Equinoxes than the Solstice season at UNEC, although they are about the same range. Also, TEC values are observed to be slightly higher for all hours and seasons at Enugu in the south than Zaria in the north except during March equinox at Zaria where TEC values were higher during the daytime. This implies that there could be little variations in TEC even within the same latitudinal zone.

scholarly journals Spatial, Seasonal, and Solar Cycle Variations of the Martian Total Electron Content (TEC): Is the TEC a Good Tracer for Atmospheric Cycles?

2018 ◽  
Vol 123 (7) ◽  
pp. 1746-1759 ◽  
Author(s):  
Beatriz Sánchez-Cano ◽  
Mark Lester ◽  
Olivier Witasse ◽  
Pierre-Louis Blelly ◽  
Mikel Indurain ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Total Electron Content ◽  
Electron Content ◽  
Total Electron ◽  
Good Tracer

scholarly journals Modeling Total Electron Content derived from radio occultation measurements by COSMIC satellites over the African Region

2019 ◽  
Author(s):  
Patrick Mungufeni ◽  
Claudia Stolle ◽  
Sripathi Samireddipalle ◽  
Yenca Migoya-Orué ◽  
Yong Ha Kim
Keyword(s):  
Total Electron Content ◽  
Local Time ◽  
Radio Occultation ◽  
Mean Squared Error ◽  
Electron Content ◽  
Quiet Time ◽  
African Region ◽  
Total Electron ◽  
Flux Level ◽  
Binned Data

Abstract. This study developed a model of Total Electron Content (TEC) over the African region. The TEC data were derived from radio occultation measurements done by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. Geomagnetically quiet time (Kp  −20 nT) data during the years 2008–2011, and 2013–2017 were binned according to local time, seasons, solar flux level, geographic longitude, and dip latitude. Cubic B splines were fitted to the binned data to obtain the model. The model was validated using TEC data of the years 2012 and 2018. The validation exercise revealed that, approximation of observed TEC data by our model produces root mean squared error of 4.8 TECU. Moreover, the modeled TEC data correlated highly with the observed TEC data (r = 0.93). Our model is the first attempt to predict TECs over the entire African region by using extensive COSMIC TEC measurements. Due to the extensive input data and the good modeling technique, we were able to reproduce the well-known features such as local time, seasonal, solar activity, and spatial variations of TEC over the African region.

scholarly journals Improved characterization and modeling of equatorial plasma depletions

2018 ◽  
Vol 8 ◽  
pp. A38 ◽  
Author(s):  
Estefania Blanch ◽  
David Altadill ◽  
Jose Miguel Juan ◽  
Adriano Camps ◽  
José Barbosa ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Local Time ◽  
Satellite System ◽  
Global Scale ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Time Duration ◽  
Total Electron ◽  
Latitude Belt ◽  
Independent Observations

This manuscript presents a method to identify the occurrence of Equatorial Plasma Bubbles (EPBs) with data gathered from receivers of Global Navigation Satellite System (GNSS). This method adapts a previously existing technique to detect Medium Scale Travelling Ionospheric Disturbances (MSTIDs), which focus on the 2nd time derivatives of total electron content estimated from GNSS signals (2DTEC). Results from this tool made possible to develop a comprehensive analysis of the characteristics of EPBs. Analyses of the probability of occurrence, effective time duration, depth of the depletion and total disturbance of the EPBs show their dependence on local time and season of the year at global scale within the latitude belt from 35°N to 35°S for the descending phase of solar cycle 23 and ascending phase of solar cycle 24, 2002–2014. These results made possible to build an EPBs model, bounded with the Solar Flux index, that simulates the probability of the number of EPBs and their characteristics expected for a representative day at given season and local time (LT). The model results provided insight into different important aspects: the maximum occurrence of bubbles take place near the equatorial anomaly crests, asymmetry between hemispheres and preferred longitudes with enhanced EPBs activity. Model output comparisons with independent observations confirmed its soundness.

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