The investigation of changes in the ionospheric total electron content (TEC) at magnetic conjugate points for geomagnetic active conditions

In this thesis, the responses of the measured total electron content (TEC) values obtained at magnetic conjugate points in the geomagnetic active state were examined. The investigation was doing for five magnetic conjugate stations, Nakatane-Katherine (22.16o N, 202.3o E and 24.16o S, 202.3o E) from the low latitude region, three from the mid-latitude (Beijing-Learmonth (30.63o N, 187.96o E and 31.86o S, 187.35o E), Petropavlovsk-Canberra (46.28o N, 227.29o D to 46.90o S, 228.33oD), Bar Harbor-Palmer Station (50.82o N, 9.26o D to 51, 31o S, 7.67o E)) and Ny Alesund-Davis (76.36o N, 129.44o E and 76.52o S, 131.76o E) from the high latitude region. The scattering diagram, superposed epoch analysis (SEA) and multiple linear regression analysis were used in the analysis. These analyzes were conducted for 4 different seasonal periods when magnetic storms occurred in 2015, when the number of sunspots was maximum. For each seasonal period, the day when the value was the maximum was taken as a reference, ± 45 days before and after this date were examined. In the SEA method, > 2+ values were determined as the moment of the event and the geomagnetic activity state was included in the analysis. In the regression model, the value of is considered as an independent variable. In addition, with the idea that the transport process will be two-way in magnetic conjugate points, the TEC value at each magnetic conjugate point was considered as the dependent variable, while the TEC value at the other point was accepted as the independent variable. It is determined that there is a strong and positive relationship in all periods for magnetic conjugate points selected from low and middle latitude regions in scattering diagrams. A very weak relationship is observed in the magnetic conjugate points selected from the high latitude region. In SEA analyzes, TEC values obtained from all magnetic conjugate points reacted around the event moment of the geomagnetic activity. This response is determined as positive or negative relative to magnetic conjugate points. In the results of multiple linear regression analysis, TEC coefficients is positive in all periods except the 2nd period of the Petropavlovsk-Canberra and the 4th period of the Bar Harbor-Palmer Station conjugate stations points. It is seen that these coefficients decrease as we go to the poles at the equator. It is seen that the geomagnetic index (Kp) value included in the model has quite low values in TEC values at the magnetic conjugate point. In other words, it has been observed that the TEC value in one of a magnetic conjugate points affects the TEC value at the opposite end much more than the index. As a result, it is seen that TEC values at magnetic conjugate points in the geomagnetic active state affect each other significantly. For this reason, especially in ionospheric derived or ionospheric studies, it is recommended to consider the changes in the opposite conjugate point when examining the change in any conjugate point and to look at the response of the TEC values during magnetic storm periods in determining the conjugate points.