Analysis of Geomagnetic Storm Effects on GNSS TEC during Ascending Phase of Solar Cycle 25: A Case Study of (12 May, 17 April and 04 November 2021) Geomagnetic Storm at Abuja and Calabar Nigeria

This research was conducted in 2022, GNSS data were obtained in the Receiver Independent Exchange (RINEX) format. Retrieval analysis software developed by Gopi Seemela was utilized to extract vertical total electron content (vTEC) data, Disturbance Storm Time (DST) indices were employed for the purposes of storm detection and categorization. MATLAB was utilized to calculate the average TEC at hourly intervals. Additionally, the background diurnal TEC was determined by taking the median of the TEC values for 10-days period preceding and following the occurrence of storm events. By comparing the observed TEC to the background TEC, the response of TEC to the storm can be estimated. The results of this analysis show that during the May 12, 2021 geomagnetic storm event recorded in Abuja and Calabar stations. The maximum TEC recorded for Abuja station during the storm was 34 TECU, but the baseline TEC measurement was 28 TECU. Consequently, there was a 21.4% surge in TEC during the period; the peak value of the observed TEC during the storm was 29 TECU, while the corresponding background TEC value was 25 TECU, which gives a percentage increase of 20.8% during the time of the storm for Calabar station. Likewise, the storm event which occurred on November 04, 2021 recorded by Abuja station showed an increasing TEC value of 53 TECU, in contrast to the equivalent background value of 37 TECU. This suggests a percentage rise of approximately 43.2%. More also, the storm event which occurred on April 17, 2021 registered by Calabar station displayed a positive TEC response. The observed TEC was greater than the background TEC, especially after the storm peak time. In conclusion, the analysis of all the storm events recorded at Abuja and Calabar stations revealed significant TEC enhancement in comparison with the quiet days’ condition in all the stations. The results of this work will provide useful data which may assist system operators or any application that relies on GNSS data for effective operation.