Features of ionospheric total electron content over high latitude regions during geomagnetic storm of November 04, 2021Variations of TEC over high latitude regions during geomagnetic storm

In this study, the features of ionospheric total electron content (TEC) over four stations in the northern and southern hemispheres during the geomagnetic storm on November 4, 2021, were studied. This study was based on GPS-TEC data obtained from University NAVSTAR Consortium dual-frequency GPS devices over Tromso, Nyal, Riga, and Svetloe in the northern stations and Majak, Steward, Wilson, and Woollard in the southern stations. The impact of solar activity on the ionospheric TEC was analysed using the continuous wavelet transform and power spectral density analysis and found to have strong coherence. The results indicate that southern hemisphere stations have higher values of changes in TEC and power spectrum change than northern hemisphere stations. Also, a highly negative impact on TEC is measured predominantly at southern stations compared with northern stations. Interestingly, the midnight TEC became higher and more comparable to the daytime TEC over southern stations than over northern stations. This might be due to the ingestion of additional plasma from higher latitudes at the southern stations. However, the values of TEC were higher during the local daytime at the northern stations. On November 4, 2021, when the IMF Bz was moving southward and sharply incremental Kp values and plasma speed were observed, the enhancement of dTEC and TEC uncertainty were more pronounced at southern stations than at northern stations. In addition, during the main phase of the storm, the spatial gradient enhancement or depletion of TEC over two stations in the northern hemisphere was larger than that of the two stations in the southern hemisphere around the day-side hours.