Generation of Pre-Sunrise Equatorial Plasma Bubbles Under the Influence of Geomagnetic Storms Based on ROTI Maps Over Indonesia

Equatorial Plasma Bubble (EPB) is a plasma irregularity in the ionosphere that occurs in equatorial to lowlatitude regions. This irregularity can cause amplitude fluctuations and phase errors in radio signals, potentially disrupting communication and satellite navigation. The growth rate of EPB can either increase or be inhibited due to changes in the equatorial zonal electric field during geomagnetic storms. This study investigates the development of EPB during the presunrise period under the influence of geomagnetic storms on May 11, 2024, and January 1, 2025, using Rate of Total Electron Content (TEC) change Index (ROTI) map analysis over Indonesia. ROTI map data were obtained from the GNSS InaCORS network and analyzed to observe EPB generation from post-sunset to pre-sunrise. The results indicate that EPB development is influenced by the Prompt Penetration Electric Field (PPEF) during the main phase of the storm and the Disturbance Dynamo Electric Field (DDEF) during the recovery phase. During the May 11, 2024, storm, post-sunset EPB did not form due to the westward DDEF, which suppressed the Rayleigh-Taylor Instability (RTI) growth rate. However, presunrise EPB developed for more than nine hours due to the eastward DDEF. Meanwhile, the January 1, 2025, storm generated post-sunset EPB that persisted until pre-sunrise due to a combination of eastward PPEF and eastward DDEF. These findings suggest that geomagnetic storms can extend the duration of post-sunset EPB and trigger new EPB formation during the pre-sunrise period.