Solar activity and geomagnetic storm e ects on GPS ionospheric TEC over Ethiopia
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Date
2017-08
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Addis Ababa University
Abstract
Ionospheric GPS total electron content (TEC) is an important parameter to monitor
for possible Space Weather impacts. The e ects of solar activity on TEC at low
latitude stations with geographic locations (latitude, longitude) of Addis Ababa (9:040
N, 38:770 E) and Bahir Dar (11:60 N, 37:360 E) in Ethiopia, East Africa in the
year of 2015 around peak of solar cycle 24 has been carried out. The data from
the two stations were used to study the diurnal, monthly and seasonal variations of
TEC and its dependence with solar activity and space weather e ects. The results
of the analysis reveal that TEC undergoes diurnal and seasonal variations. From
the daily variation analysis, the TEC value at both stations sharply increases to its
peak value from 0900 �� 1500 UT and decreases around 1600 �� 0700 UT. Seasonal
variations showed that TEC maximizes during the equinoctial months and least in
summer, over the two stations. In all seasons the maximum value of TEC leads rst
in Addis Ababa. These observations were investigated and further discussed with an
analysis of Disturbance Storm Time (Dst) and Ap indices, solar radio
ux (F10.7
cm) and sunspot number during the period of 2015. During the period of low or
high sunspot number, the provided GPS ionospheric TEC builds up slowly or quickly.
As a typical case of storm-time behavior, a geomagnetic storm of June 23, 2015 is
considered in this study. The Dst values for the period shows that it is an intense
intensity geomagnetic storm. The e ects of geomagnetic storms on TEC values have
been found negative and positive output.
Keywords: Solar activity, GPS, Ionosphere, TEC, Geomagnetic storm,
Ethiopia.
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Keywords
Solar activity, GPS, Ionosphere, TEC, Geomagnetic storm, Ethiopia