Variability of ionospheric TEC at low latitude station, Hyderabad during medium solar activity

The successful operation of communicational and navigational applications requires knowledge of state and behaviour of ionosphere as well as spatial and temporal changes taking place in it. With this view, we have studied the variability and changes in the low latitude ionosphere by considering a low latitude Indian station Hyderabad (17.41 degrees N, 78.55 degrees E). The variability is studied during the year 2014, by using the space borne Global Positioning System (GPS) observations. From GPS observations an important parameter; Total Electron Content (TEC) is obtained, which represents the integral electron density of the ionosphere and is widely used in studies concerning ionospheric variability. We have studied how the ionospheric conditions at Hyderabad change from hour to hour, day to day, month to month and season to season. We found that ionosphere over Hyderabad exhibits significant, interesting and regular variability. Although, the trends followed by the ionospheric changes are similar, but the magnitude of peak values differ on different time scales. Finally we have compared the variability of observed or actual values of TEC with the corresponding values predicted by International Reference Ionosphere (IRI) model-2016 and found good agreement between hourly values, while IRI model overestimates or underestimates the daily values.