Ionospheric Disturbances at Low-latitude during Severe Geomagnetic Storm Events

Abstract In this paper, we investigated the characteristics of Total Electron Content (TEC) using Global Navigation Satellite System (GNSS) satellites at low-latitudes during geomagnetic storms, focusing on the severe geomagnetic storm events that occurred on March 24, 2023, and April 23–24, 2023. The GNSS receiver stations at low-latitude are situated in Bangkok, (13.729°N, 100.780°E) and Chumphon (10.724°N, 99.375°E), Thailand. The TEC data were collected from three sources: GNSS satellites receivers, International GNSS Service (IGS), and International Reference Ionosphere (IRI). We compared the GPS TEC, IGS TEC, and IRI TEC. Subsequently, we examined the correlation between the levels of geomagnetic storms and ionospheric TEC disturbances. The results showed that the geomagnetic storm levels correspond to ionospheric TEC disturbances. We found that during the occurrence of a geomagnetic storm, TEC values tend to continuously increase and then return to normal within a few days. During the storm events, TEC values were increased by approximately 10–35 percent over Bangkok and up to 75 percent over Chumphon. The correlation between the geomagnetic storms levels and TEC disturbances are found to be significantly associated with the intensity of geomagnetic storms. An increase in the intensity of strong geomagnetic storms, there are positive correlations with higher TEC values. However, during quiet periods, TEC maintains its normal levels without showing a decrease below the baseline value, indicating a negative correlation observed.