GPS derived TEC and foF2 variability at an equatorial station and the performance of IRI-model

Adebiyi, S.J.; Odeyemi, Olumide Olayinka; Adimula, I. A.; Oladipo, O.A.; Ikubanni, S.O.; Adebesin, B.O.; Joshua, B.W.

doi:10.1016/j.asr.2014.03.026

Cited by 21 publications

(21 citation statements)

References 33 publications

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“…At present, most TEC measurements are retrieved from Global Positioning System (GPS) receivers (Bolaji et al, 2012(Bolaji et al, , 2013Adebiyi et al, 2014). Evidences have shown that similar features observed from these aforementioned older works at low latitudes are as well revealed by GPS obser vations in Africa.…”

Section: Introductionmentioning

confidence: 81%

“…The ionosphere, especially its F2-layer height and its topside, is influenced by several factors, which include but not limited to time of the day, seasons, geographical locations, and the Sun's activity (Adeniyi, 2007). In characterizing the ionosphere, several parameters such as the critical frequency (foF2), maximum electron density of the F2-layer (NmF2) and the height-integrated total electron content (TEC), which factored-in the total column of electron per unit surface area of the ionosphere have been investigated (Bolaji et al, 2013;Ikubanni and Adeniyi, 2014;Adebiyi et al, 2014). These three ionospheric parameters have been reported to share similar features (Gupta and Singh, 2001;Chen et al, 2009;Adewale et al, 2012) due to the couplings of the topside with the bottom side electron density.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of a low and a middle latitude GPS-TEC in Africa during different solar activity levels

Bolaji¹,

Kotoye²,

Ikubanni³

et al. 2018

Ife Journal of Science

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In this work, we compared TEC values at Libreville (a low latitude station) with Sutherland (a middle latitude station) over Africa using Global Positioning System (GPS) receivers during high solar activity (HSA), moderate solar activity (MSA) and low solar activity (LSA). Apart from our confirmation that high, moderate and low values of TEC responded well to HSA, MSA and LSA, respectively at the low and middle latitude, equatorial ionization anomaly (EIA) played significant roles as regard higher values of TEC at Libreville compared to Sutherland. Interestingly, the TEC difference between a low and middle latitude revealed how EIA is majorly responsible for the occurrence of pre-reversal enhancement (PRE) in equinoctial months at Libreville. In addition, TEC difference majorly due to EIA is inactive around pre-sunrise and sunrise hours on some days during HSA and MSA. However, it is always active on all hours in all of the days during LSA. The obliterated semi-annual signature seen during HSA of seasonal difference in TEC magnitude is significantly associated with inactive EIA around 0400 LT-0900 LT during March equinox, September equinox and December solstice.

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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Comparison of a low and a middle latitude GPS-TEC in Africa during different solar activity levels

Bolaji¹,

Kotoye²,

Ikubanni³

et al. 2018

Ife Journal of Science

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“…The equatorial ionization anomaly (EIA) region is a hotspot for validating studies on the IRI-2012 model. Comparison studies with GPS-derived TEC have validated the performance results of the IRI-2012 model over years of varied solar activity in different EIA regions (Bhuyan and Hazarika 2013, Nogueira et al 2013, Arunpold et al 2014, Asmare et al 2014, Adebiyi et al 2014, Karia et al 2015, Leong et al 2015, Panda et al 2015, Rabiu et al 2014. Given the predict ability of the diurnal variation of TEC, deficiencies have varied with local time, season, and latitude.…”

Section: Introductionmentioning

confidence: 88%

Variability of Ionospheric TEC and the Performance of the IRI-2012 Model at the BJFS Station, China

Peng

2016

Acta Geophys.

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A b s t r a c tWe studied variation characteristics of ionospheric total electron contents (TEC) and performance of the International Reference Ionosphere (IRI)-2012 model in predicting TEC at the BJFS (Beijing Fangshan station), China. Diurnal and seasonal variations were analyzed with TEC data derived from dual-frequency global positioning system (GPS) observations along with the solar activity dependence of TEC at the BJFS station. Data interpolated with information from IGS Global Ionosphere Maps (GIMs) were also used in the analysis. Results showed that the IRI-2012 model can reflect the climatic characteristics and solar activity dependence of ionospheric TEC. By using time series decomposition method, ionospheric daily averaged TEC values were divided into the periodic components, geomagnetic activity component, solar activity component and secular trend. Solar activity component and periodic components are supposed to be the main reasons which account for the difference between the GIMs TEC and the TEC from the IRI-2012 model.

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“…In the African equatorial sector, Nigussie et al (2013) noticed that NeQuick 2 was more accurate during epochs with moderate solar activity than dur-ing epochs characterised by low solar activity. Ahoua et al (2014) investigated the performance of NeQuick 1 (NeQuick ITU-R) in modelling the daily TEC over the South African region, taking into account both solar and magnetic conditions. It was reported that NeQuick 1 did not perform well during the epochs of maximum solar activity.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)

et al. 2018

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Abstract. In order to provide a scientific base to the NeQuick characterisation under disturbed conditions, the comparison of its performance for quiet and storm days is investigated in the southern mid-latitude. This investigation was realised using the two versions of the NeQuick model which were adapted to local and storm-specific response by using the critical frequency of the F2 layer (foF2) and the propagation factor (M(3000)F2) derived from three South African ionosonde measurements, Hermanus (34.40∘ S, 19.20∘ E), Grahamstown (33.30∘ S, 26.50∘ E) and Louisvale (28.50∘ S, 21.20∘ E). The number of free electrons contained within a 1 m squared column section known as total electron content (TEC) is a widely used ionospheric parameter to estimate its impact on the radio signal passing through. In this study, the TEC derived from the adapted NeQuick version is compared with observed TEC derived from Global Navigation Satellite System (GNSS) data from co-located or nearby GNSS dual-frequency receivers. The Hermanus K-index is used to select all the disturbed days (K-index ≥ 5) upon moving from low to high solar activity (from 2009 to 2012). For each disturbed day, a quiet reference day of the same month was chosen for the investigation. The study reveals that the NeQuick model shows similar reliability for both magnetic quiet and disturbed conditions, but its accuracy is affected by the solar activity. The model is much better for moderate solar activity epochs (2009 and 2010), while it exhibits a discrepancy with observations during high solar activity epochs. For instance in Hermanus, the difference between GPS TEC and NeQuick TEC (ΔTEC) is generally lower than 10 TECu in 2009, and it sometimes reaches 20 TECu in 2011 and 2012. It is also noticed that NeQuick 2 is more accurate than NeQuick 1, with an improvement in TEC estimation more significant for the high solar activity epochs. The improvement realised in the latest version of NeQuick is more than 15 % and sometimes reaches 50 %. Keywords. Ionosphere (mid-latitude ionosphere; modelling and forecasting)

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GPS derived TEC and foF2 variability at an equatorial station and the performance of IRI-model

Cited by 21 publications

References 33 publications

Comparison of a low and a middle latitude GPS-TEC in Africa during different solar activity levels

Comparison of a low and a middle latitude GPS-TEC in Africa during different solar activity levels

Variability of Ionospheric TEC and the Performance of the IRI-2012 Model at the BJFS Station, China

Evaluation of the NeQuick model performance under different geomagnetic conditions over South Africa during the ascending phase of the solar cycle (2009–2012)

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