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European Journal of Applied Sciences – Vol. 11, No. 3
Publication Date: June 25, 2023
DOI:10.14738/aivp.113.14513.
Dinga, J. B., Okolandzaud, O. P., Poaty, J. F.-P. B., & Biona, C. B. (2023). Estimated Impacts Induced by The Magnetic Activity Index
(Dst) on the Local Total Electronic Content (TEC) in Africa Equatorial Zone. European Journal of Applied Sciences, Vol - 11(3). 291-
309.
Services for Science and Education – United Kingdom
Estimated Impacts Induced by The Magnetic Activity Index (Dst)
on the Local Total Electronic Content (TEC) in Africa Equatorial
Zone
Jean Bienvenu Dinga
Institut National de Recherche en Sciences Exactes et Naturelles(IRSEN),
Ministère de la Recherche Scientifique et de l’innovation Technologique,
Avenue de l’Auberge Gascogne, Cité Scientifique (ex-ORSTOM), Château d’eau,
Brazzaville, République du Congo and Faculté des Sciences et techniques,
Université Marien Ngouabi, République du Congo
Oba Péa Okolandzaud
Faculté des Sciences et techniques, Université Marien Ngouabi,
République du Congo
Jocelyn Franck-Patient Boungou Poaty
Institut National de Recherche en Sciences Exactes et Naturelles(IRSEN),
Ministère de la Recherche Scientifique et de l’innovation Technologique,
Avenue de l’Auberge Gascogne, Cité Scientifique (ex-ORSTOM), Château d’eau,
Brazzaville, République du Congo and Faculté des Sciences et techniques,
Université Marien Ngouabi, République du Congo
Clobite Bouka Biona
Institut National de Recherche en Sciences Exactes et Naturelles(IRSEN),
Ministère de la Recherche Scientifique et de l’innovation Technologique,
Avenue de l’Auberge Gascogne, Cité Scientifique (ex-ORSTOM), Château d’eau,
Brazzaville, République du Congo and Faculté des Sciences et techniques,
Université Marien Ngouabi, République du Congo
ABSTRACT
The state of equatorial ionosphere has been studied from the determination of the
Total Electron Content (TEC) based on the correction of errors propagation of GPS
signals due to ionospheric disturbances using the dual frequency method. In our
study, we considered tree stations of the equatorial area (adis, bjco and nklg) in
January 2012. Firstly, the monthly survey of the TEC has revealed that the magnetic
storm days coincide with the days that the TEC Rinex around 70 UCET. Secondly, the
daily survey of the TEC reveals two TEC (TEC/RINEX and the TEC/CODG) has
revealed that during magnetics storms days, the interval between curves of TEC
observed between 10: 00PM to 16:00PM (UT) is more important (around 10 UCET)
when the Dst is strongly negative whatever the nature of the magnetic storm, and
the interval between curves of TEC observed between 17:00 to 20:00PM (UT) is
function of the nature of the magnetic storm.
Keywords: Total Electron Content, magnetic storm, Ionosphere and equatorial zone.
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Services for Science and Education – United Kingdom 292
European Journal of Applied Sciences (EJAS) Vol. 11, Issue 3, June-2023
INTRODUCTION
This study falls within the context of the influence of magnetic storms on the ionosphere in the
equatorial region. Indeed, the Sun ejects a flow of particles called solar wind which interacts
with the magnetic field of the Earth. Part of this solar wind can penetrate the magnetosphere
and reach the ionosphere causing several effects including geomagnetic activity. This activity
greatly disturbs the ionosphere which in turn disturbs the propagation of radio waves. A
number of magnetic indices have been defined to quantify this activity [1]. Only the Dst
(Disturbance Storm Time) index will be used in this study. The Dst describes the effect of
geomagnetic activity on the ionosphere. It is obtained by a network of geomagnetic
observatories near the equator, which globally measure the intensity of the equatorial
electrojet [2]. The electrojet is a strong electronic and ionic current located in the E region of
the ionosphere and whose maximum intensity is at an altitude of 105 km [3]. The ionosphere
is the layer of the upper atmosphere permanently subject to the influence of solar activity. This
is the ionized region of the Earth's atmosphere. According to Gauss, the ionosphere is the seat
of currents responsible for variations in the Earth's magnetic field [4]. The ionosphere is
composed of several layers of different thicknesses in which the ionization varies according to
the day, the season, the latitude and the solar activity [5]. Particularly, we limited our study to
the equatorial ionosphere characterized by a high electron density. The diagnosis of the
equatorial ionosphere consists of studying the phenomena that govern and disturb the sun- earth system, including equatorial magnetic disturbances.
Numerous studies have shown that disturbances in the ionosphere, regardless of the cause,
affect the propagation of GPS (Global Position System) signals [6]. The GPS is an effective tool
for the study of the ionosphere in the measurement of the Total Electronic Content (TEC) along
the satellite-earth path that we note TEC (Total Electron Content). TEC is the number of free
electrons in the ionosphere encountered by signals from GPS satellites along their path to the
GPS receiver.
Similarly, it is well known that the effects of magnetic storms on the ionosphere are very
significant, but these effects on the TEC are very weak [7]. In this study, the scientific question
that arises is whether the variation of the local TEC over the equatorial region is strongly
dependent on the Dst.
The data we have to study this aspect is a temporal model of the free electron content of the
ionosphere on a global scale. This model was built by Rolland Fleury of the Institut Télécom- Bretagne [8] based on ionospheric data from GPS. These data were obtained thanks to the
Research Group in Exact and Natural Sciences (GRSEN) in collaboration with the International
Research Group in Geophysics Europe Africa (GIRGEA). We apply this model to the ionospheric
measurements of the three GPS stations located in equatorial Africa. For technical reasons, we
used GPS data from nklg stations in Gabon, bjco stations in Benin and adis stations in Ethiopia
throughout January 2012.
To answer our concern, we propose to show that using the calculation of the TEC, the variation
of the local TEC noted TEC RINEX is a function of the Dst index in the equatorial zone. Achieving
our main objective requires three specific objectives:
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293
Dinga, J. B., Okolandzaud, O. P., Poaty, J. F.-P. B., & Biona, C. B. (2023). Estimated Impacts Induced by The Magnetic Activity Index (Dst) on the Local
Total Electronic Content (TEC) in Africa Equatorial Zone. European Journal of Applied Sciences, Vol - 11(3). 291-309.
URL: http://dx.doi.org/10.14738/aivp.113.14513.
• determine the TEC by the local model TEC RINEX from the RINEX format file
(ReceiverIndependent Exchange) and the TEC by the global TEC model CODG (Center
for OrbitDetermination in Europe for Global IonosphereMaps) from the IONEX format
file (Ionosphere Exchange);
• carry out a comparative study between the results of the local TEC RINEX treatment and
those of the global TEC CODG treatment.
• examine the differences (ΔTEC = TEC RINEX -TEC CODG) between the curves of the TEC
(TEC RINEX and TEC CODG) to the variation of the Dst during the same period.
.
Site Description
Fig. 1: Location map of GPS stations in the study area
Our study is focused on the ionosphere above Africa in the equatorial region. The equatorial
region is located 30° latitude on either side of the magnetic equator. In the equatorial zone of