Role of Space Weather in Determining the State of the Ionosphere

The influence of space weather on the state of the ionosphere is most pronounced during disturbances. In the present paper, this effect is estimated from changes of the total electron content TEC and the critical frequency foF2. For the study, March 2012 was selected, which includes two periods: March 7-17 and March 21-31. The first period includes four strong magnetic storms and is well documented in the literature in terms of the behavior of solar and geomagnetic parameters. The second period is characterized by an increase in TEC over almost the entire period. Latitudinal variations of TEC in the range 30° - 80° N near the meridian of 15° E and their correlation coefficients with solar and geomagnetic parameters are obtained. Using vertical sounding data (foF2) for four European stations near the selected meridian, the latitudinal dependence of the equivalent slab thickness of the ionosphere was constructed over the entire range. This dependence made it possible to obtain the latitudinal response of the frequency foF2 on disturbances and to reveal features such as the transition from the zone of negative disturbances at high latitudes to positive disturbances at low latitudes in the first period, daily excess over the median in the second period. This response was compared with frequency behavior for the International Reference Ionosphere model IRI. It was shown that the IRI model does not adequately reflect the variation of foF2 during disturbances, however, an assessment of the latitudinal dependence of the accuracy of the model, when compared with the median, showed that the model provides results for the high-latitude region at level of the middle-latitude values with a decrease in accuracy with decreasing latitude.