The main aim of this thesis is to explore how solar activity impacts the upper atmosphereabove Addis Ababa, Ethiopia, situated at 9.040°N and 38.770°E. Spanning from 2012 to 2016, the study employs ground-based GPS data to delve into ionospheric characteristics.Drawing data from sources like IMF Bz, F10.7, and SSN via the OMNI Web data Explorerand UNAVCO, the investigation seeks to unravel the interplay between solar activity and ionospheric fluctuations. By analyzing a rich dataset encompassing GPS Total Electron Content (TEC) and solar activity indices, the study aims to elucidate how solar phenomena influence the ionosphere. The results indicate a clear correlation between solar activity andTEC enhancement, underscoring the Sun's pivotal role in ionization processes and TEC modulation. Additionally, the research reveals diurnal trends in TEC values, peaking aroundmidday and dipping during nighttime hours. These insights shed light on the intricatedynamics between solar activity and the upper atmosphere, particularly in the context of Ethiopia. The implications of these findings extend to enhancing our grasp of space weatherimpacts and advancing predictive models for ionospheric conditions in the region.