Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

Oryema, Bosco; Jurua, Edward; D’ujanga, Florence Mutonyi; Ssebiyonga, N.

doi:10.1016/j.asr.2015.05.037

Cited by 27 publications

(6 citation statements)

References 57 publications

(72 reference statements)

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“…The concentration reaches a maximum at autumnal equinox and a minimum at summer solstice. Similar results have been found in previous study ( [10], [11]).…”

Section: Seasonalsupporting

confidence: 93%

Equatorial Ionosphere Characterization for Sub-Saharan Africa SBAS

Foucault¹,

Blelly²,

Marchaudon³

et al. 2018

Proceedings of the 31st International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS+ 201

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He is a specialist in numerical modelling of terrestrial ionosphere and developed numerous models, the TRANSCAR/IPIM family models, which are now acknowledged as reference models for the study of the high latitude ionosphere. Dr. Aurélie Marchaudon is a permanent CNRS researcher at IRAP (Toulouse, France). Her work has been dedicated to a better understanding of the magnetosphere-ionosphere coupling by combining ground-based instrumentation like SuperDARN radars and space-borne instruments and simulation from ionosphere models (TRANSCAR, IPIM). Since 2008, she is the SuperDARN PI of the French Kerguelen radar.

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“…The concentration reaches a maximum at autumnal equinox and a minimum at summer solstice. Similar results have been found in previous study ( [10], [11]).…”

Section: Seasonalsupporting

confidence: 93%

Equatorial Ionosphere Characterization for Sub-Saharan Africa SBAS

Foucault¹,

Blelly²,

Marchaudon³

et al. 2018

Proceedings of the 31st International Technical Meeting of the Satellite Division of the Institute of Navigation (ION GNSS+ 201

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“…Consequently, this may delay the decay time of the plasma, thus resulting in the abnormally slightly higher VTEC values recorded at the UUMK station. Similarly, Oryema observed the variations in VTEC data obtained in 2012 at different stations over African regions [42]. They found that the Addis Ababa station located near the magnetic equator recorded the highest VTEC values as compared to other stations.…”

Section: Resultsmentioning

confidence: 85%

Evaluating the Performance of IRI-2016 Using GPS-TEC Measurements over the Equatorial Region

2021

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Total electron content (TEC) is an important parameter in the ionosphere that is extensively used to study the variability of the ionosphere as it significantly affects radio wave propagations, causing delays on GPS signals. Therefore, evaluating the performance of ionospheric models is crucial to reveal the variety of ionospheric behaviour in different solar activity periods during geomagnetically quiet and disturbed periods for further improvements of the IRI model performance over the equatorial region. This research aimed to investigate the variations of ionospheric VTEC and observe the improvement in the performance of the IRI-2016 (IRI-2001, IRI01-corr, and NeQuick). The IRI-2016 was evaluated with the IRI-2012 using NeQuick, IRI-2001, and IRI01-corr topside electron density options. The data were obtained using a dual-frequency GPS receiver installed at the Universiti Utara Malaysia Kedah (UUMK) (geographic coordinates 4.62° N–103.21° E, geomagnetic coordinates 5.64° N–174.98° E), Mukhtafibillah (MUKH) (geographic coordinates 6.46° N–100.50° E, geomagnetic coordinates 3.32° S–172.99° E), and Tanjung Pengerang (TGPG) (geographic coordinates 1.36° N–104.10°E, geomagnetic coordinates 8.43° S–176.53° E) stations, during ascending to high solar activity at the geomagnetically quiet and disturbed periods in October 2011, March 2012, and March 2013. The maximum hourly ionospheric VTEC was observed during the post-noon time, while the minimum was during the early morning time. The ionospheric VTEC modelled by IRI-2016 had a slight improvement from the IRI-2012. However, the differences were observed during the post-noon and night-time, while the modelled VTEC from both IRI models were almost similar during the early morning time. Regarding the daily quiet and disturbed period’s prediction capability of the IRI-2016 and IRI-2012, IRI-2016 gave better agreement with the measured VTEC. The overall results showed that the model’s prediction performance during the high solar activity period in 2013 was better than the one during the ascending solar activity period. The results of the comparison between IRI-2016 and IRI-2012 in high solar activity exhibited that during quiet periods, all the IRI models showed better agreement with the measured VTEC compared to the disturbed periods.

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“…Reference TEC began to increase from 05:00 LT in all latitudes, and reached their peaks at 12:40 LT–13:18 LT from

63 °

33 °

N, as shown by the dotted line in the panel. They decreased and remained at a small value after sunset when the solar radiation disappeared (Oryema et al., 2015).…”

Section: Resultsmentioning

confidence: 99%

Characteristics of Ionospheric Storm on October 13, 2016 at the Greenwich Meridian

Wan

Maruyama

et al. 2021

JGR Space Physics

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The geomagnetic storms are the disturbances of the Earth's magnetic field, and the impact of solar wind particles enhancement (Buonsanto, 1999;Gonzalez et al., 1994;Kumar & Kumar, 2019). Following geomagnetic storms, the ionosphere also has obvious disturbance. It shows the critical frequency of F2-layer (foF2) or total electron content (TEC) changes obviously. The large decrease of foF2 or TEC is the ionospheric negative storm, and the significant increase of foF2 or TEC is referred to as positive storms (Fagundes et al., 2016;Maruyama et al., 2004). In general, 𝐴𝐴 𝐴𝐴 region ionization is positively correlated to the density ratio of atomic oxygen [O] to the molecular nitrogen 𝐴𝐴 [N2] . Prölss (1987) showed that the negative storm was caused by the change of neutral gas composition. The enhanced ratio of 𝐴𝐴 [N2] /[O] would lead to the chemical loss rate increase, so the ionospheric electron density decreased.There are two main physical mechanisms of ionospheric positive storms. The first is the equatorward wind surge or disturbance wind (Fuller-Rowell et al., 1994). Joule heating raises the temperature of the upper thermosphere and ion drag drives high velocity neutral winds. The heat source drives a global disturbance wind. It propagates to low latitudes and even into the opposite hemisphere. The equatorward wind pushes the ionosphere up to high altitudes where the recombination is ineffective. As a result, the electron density increases under sunlit conditions (Maruyama et al., 2004;Zhao et al., 2008). Because the equatorward wind surge blows from high to low latitudes, the ionospheric disturbance has time delay. During quiet days, the neutral winds (or background winds) are poleward in daytime and turn equatorward after sunset. During storms, the neutral winds are the combination of background and disturbance winds. The daytime neutral wind, which is caused by Joule heating in the auroral region, even turns to equatorward (Fuller-Rowell et al., 1994). Different storms have different intensity, local time, and latitude coverage. de Jesus et al. ( 2016) studied a positive ionospheric storm at equatorial, low and middle latitudes in African sector. The factor was the equatorward disturbance winds and huge wind circulations.

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Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

Cited by 27 publications

References 57 publications

Equatorial Ionosphere Characterization for Sub-Saharan Africa SBAS

Equatorial Ionosphere Characterization for Sub-Saharan Africa SBAS

Evaluating the Performance of IRI-2016 Using GPS-TEC Measurements over the Equatorial Region

Characteristics of Ionospheric Storm on October 13, 2016 at the Greenwich Meridian

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