Analysis of VTEC and Scintillation Parameters during Very Strong Geomagnetic Storm Events at Pontianak

Geomagnetic storms, triggered by enhanced solar activity, significantly impact the Earth's ionosphere, affecting space-based technologies. These storms occur when the solar wind carries charged particles into the Earth's atmosphere, disturbing the geomagnetic field. This study analyzes ionospheric responses to strong geomagnetic storm events at Pontianak, focusing on Vertical Total Electron Content (VTEC) and scintillation parameters indicated by the S4 Index. Data were obtained from a Septentrio instrument at the Pontianak station for three events (April 24, 2023, May 11, and August 12, 2024). VTEC measurements and the S4 Index were used to identify ionospheric irregularities. VTEC increased during the storm's expansion phase in April 2023 and May 2024, but differed in August 2024, possibly due to fluctuations in solar wind speed and the interplanetary magnetic field. Strong scintillation occurred approximately one day after the Dst minimum in April 2023 and August 2024, but did not occur in May 2024. The May 2024 event showed a delayed increase in the S4 Index, potentially due to variations in the interplanetary electric field and fluctuating auroral and mid-latitude magnetic activity. This research enhances our understanding of ionospheric behavior during intense geomagnetic storms, highlighting the complex interplay between solar-terrestrial interactions and ionospheric irregularities.