Abstract:
he data collected by the ground based GPS receiver located at Adama (8.57° Nand
39.29° E) have been analyzed to study the temporal variations of the ionosphere in
)
the region. We have also investigated the effects of sunspot and geomagnetic storm
on the characteristics of the total electron content (TEC) values. We have found that
the TEC values are minimum at pre-down through out the year, followed by a steep
increase in its value in the intervals lOOOUT-1400UT. This is due to the variation of
the strength of solar radiation that reaches the atmosphere. We have observed larger
TEC values in autumn and spring seasons, and the minimum and the intermediate
TEC values in summer and winter seasons respectively. Because during the autumn
and spring the Sun is overhead at Adama station the intensity of radiation that comes
from the Sun is maximum. But during summer and winter the Sun is not overhead
at Adama and this means minimum Sun's radiation reach to the atmosphere. The
TEC values increase when the sunspot number is increase. The observed TEC values
are correlated with sunspot numbers. This is due to the fact that when there are
more
radiation(X-ray and UV) from the Sun during large number of sunspots. The
effects of the geomagnetic storm on TEC values have been found negative and positive
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correlation with geomagnetic storm.
