Variations of TEC Over Iberian Peninsula in 2015 Due to Geomagnetic Storms and Solar Flares

Abstract

The total electron content (TEC) over the Iberian Peninsula was studied using data from two locations obtained both by Global Navigation Satellite System receivers and an ionosonde. The principal component analysis applied to the TEC data allowed us to extract two main modes. Each mode is characterized by a daily TEC variation of a certain type (principal component [PC]) and its amplitude for each of the studied days (given by the empirical orthogonal functions [EOFs]). The variations of these modes as well as the original TEC data were studied in relation to four strongest geomagnetic storms of 2015 and three geomagnetic disturbances of lower amplitude observed during the same months. EOFs were found to correlate well with space weather parameters characterizing solar UV and XR fluxes, number of the solar flares, parameters of the solar wind, and geomagnetic indices. Multiple regression models were constructed to fit EOFs using combinations of the space weather parameters with a lag from 0 to 2 days. Combining the regression models of EOFs with the corresponding PCs, we reconstructed TEC variations as a function of space weather parameters observed in previous days. The possibility to use such reconstructions for the TEC forecasting was also studied. The results of the data analysis can be used to develop regional empirical models allowing prediction of ionospheric response to different forcings, for example, geomagnetic storms. In particular, the method called

Extreme Solar Events’ Impact on GPS Positioning Results

“…More information on "waves" can be found in Supplementary Materials Tables S3 and S6 and in Tables S4 and S7 for December 2014 and March 2015, respectively. [10][11][12][13][14][15]. Figure 7 and Supplementary Materials Tables S5-S7 shows the plot of simultaneously occurring discrepancies in March 2015.…”

“…Figure 7 and Supplementary Materials Tables S5-S7 shows the plot of simultaneously occurring discrepancies in March 2015. [10][11][12][13][14][15]. Figure 7 and Supplementary Materials Tables S5-S7 shows the plot of simultaneously occurring discrepancies in March 2015.…”

“…Cherniak et al [10] investigated the dynamics of the high-latitude ionospheric irregularities during 17 March 2015 (St. Patrick's Day Storm), using ground-based GPS measurements. The St. Patrick's Day geomagnetic storm has been widely considered [10][11][12][13][14][15].…”

“…The results reveal interhemispheric differences in the occurrence of ionospheric irregularities. Research on variations of the TEC over the Iberian Peninsula in 2015 was performed by Morozova et al [11], highlighting the effects of geomagnetic storms, solar flares, and solar eclipses. These authors showed that no definitive conclusions about the dependence of the TEC variation during geomagnetic storms on the season or start time can be made.…”

“…In March 2015, strong geomagnetic storms occurred, with following indices: 17 March, Kp 8-, Ap 108, 2 C-class flares, 1 M-class flare; 18 March, Kp 6, Ap 47, 18 C-class flares; 19 March, Kp 5, 2 C-class flares; 20 March, Kp 5, C-class flare. The impact of the strongest geomagnetic storm on 17th of March (St Patrick's Day) has been widely considered in many papers[10][11][12][13][14][15]. Figure7and Supplementary Materials Tables S5-S7 shows the plot of simultaneously occurring discrepancies in March 2015.…”