| dc.description.abstract |
Equatorial ionospheric (e.g. equatorial electro-jet, EEJ) irregularity is a nuisance for technologies
that depend on trans-ionospheric propagating radio waves. Significant efforts are being carried
out to understand the EEJ irregularity; however, the African equatorial ionosphere that shows
unique phenomena as observed by Low Earth Orbiting (LEO) satellite is the least investigated
due to the lack of ionospheric monitoring instruments. In this thesis the spatial, temporal and
statistical characteristics of equatorial electro-jet (EEJ) irregularities over Bahir Dar region are
investigated using data from ground based Very High Frequency (VHF) Coherent Backscatter
Radar, which is installed recently at Bahir Dar, Ethiopia and it is the first kind in Africa. One
year data have been used and Doppler power spectral and statistical techniques have been applied
to investigate the characteristics of the EEJ irregularity. It is found out that the EEJ irregularities
were occurred, most frequently, between 99 and 102 km above sea-label within the time intervals
of 10 to 14 LT (local time). Also, intense EEJ irregularities have been observed more frequently
in the March equinox than other seasons. Moreover, the returned echoes of irregularities were
found to have power spectra with peak power centered at zero or nearly zero Doppler shift. This
indicates that the most dominant class of EEJ irregularity is type II. Some power spectra with
mixture of type I and Type II were also observed in the returned echoes of the irregularities |
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