Investigation of ionospheric total electron content (TEC) fluctuation (magnetic storm, solar activity and earthqauke based) satellite based positioning system

The ionosphere layer, which contains many electrons in free form, is very important for signal based applications due to its reflective property. On the other hand, it is also important layer in terms of detecting possible changes in the upper atmosphere that may be caused by the earthquake. In the scope of this thesis, the ionospheric TEC changes related to 17 earthquakes in the world between the years of 2010-2016, Mw ≥6, were investigated. Ionospheric conditions were also taken into consideration in order to interpret the possible ionospheric TEC changes in relation to the earthquake. In the first part of the study where two different methods were applied, total of 60 days of TEC data were used and a separate k value was generated for each earthquake. A new method for earthquake analysis was developed by using the quartile method commonly used in the literature. In the other method, TEC values to be used in earthquake analysis was produced by means of the model, statistical analysis was carried out by the difference between TEC values obtained on this model and real TEC values. As a result of the study, positive or negative anomalies were obtained before and after the earthquake in most of the earthquakes analyzed. Moreover, Turkey regional ionosphere model was created from 2013 to 2015 using TUSAGA-Active system and behaviour of ionosphere layer is also investigated for this period. On the other hand, ionospheric changes caused by G4 and above magnetic storm activities are monitored, and ionosphere-earthquake, ionosphere-magnetic storm, ionosphere-solar activity relationship are revealed and regional ionosphere model is created for Turkey. In the study, where different statistical methods were applied, anomalies which may be caused by earthquakes on different or same days were obtained. It was thought that anomalies obtained on different days were caused by different statistical approaches. According to the results obtained from regional ionosphere mapping using TUSAGA-Active stations of 2013, 2014, 2015, it was seen that the year of highest ionospheric activity was 2014. In all these years, ionospheric changes were clearly revealed in all of the G4 and high magnetic storms.