Effects of 7September 5–12, 2017 solar flares on regional disturbance of Earth’s ionosphere as recorded by GNSS stations located in the Volga Federal District of the Russian Federation

The paper presents the results of estimation of the effects of September 5–12, 2017 solar flares on the regional disturbance of Earth's ionosphere according to data from a distributed network of GNSS stations located mostly in the Volga Federal District of the Russian Federation. The GNSS data processing software package we have developed is used to analyze recorded signal power and daily two-frequency phase measurements, as well as to calculate the total electron content and map the data. The results of the study show that during powerful solar flares X2.2 and X9.3 on September 6 the median value of the total electron content, calculated for the Volga Federal District, increased up to 0.25 TECU and 0.6 TECU respectively. At that time, the region of interest (40°–55° E) was sunlit. The prolonged magnetic storms on September 8 also generated noticeable ionospheric disturbances up to 0.2 TECU. At the same time, neither the solar flares nor the magnetic storms had a significant effect on the power characteristics of the recorded signals from navigation satellites in the region under study. The median carrier-to-noise ratio calculated for the region considered over the entire observation period did not differ from the values recorded under undisturbed ionospheric conditions and varied between 47–53 dBHz and 38–49 dBHz for frequencies L1 and L2 respectively.