Ionospheric scintillations associated with equatorial plasma bubbles in Southeast Asia during the ascending and maximum phases of Solar Cycle 25

This paper presents ionospheric scintillation observations in Southeast Asia during the ascending and maximum phases of Solar Cycle 25 (2020–2025). Ionospheric scintillation has been widely used to investigate equatorial plasma bubbles (EPBs) for several decades. However, such investigations have not yet been conducted in Southeast Asia during Solar Cycle 25, despite their importance in advancing our understanding of EPB behavior. In this study, we analyze the ionospheric scintillation data collected between 2020 and 2025 in Bac Lieu, Vietnam, and Chumphon, Thailand, using observations from the Southeast Asia low-latitude ionospheric network. The ionospheric scintillations intensified from the evening to the post-midnight sector, particularly during the equinoctial months (March–April and September–October) and years of higher solar activity, consistent with the general characteristics of EPBs. As solar activity increased, scintillations could occur until later post-midnight hours. Furthermore, the ionospheric scintillations tended to intensify when the main phase of geomagnetic storms occurred in the evening and weakened when the recovery phase began in the evening. The storm-time electric fields associated with the evening onset of the main and recovery phases of geomagnetic storms are likely important for the EPB intensification and suppression, respectively. Additionally, the storm-time electric fields associated with the onset of the recovery phase before sunrise can result in EPB development. Post-sunset ionospheric scintillations were suppressed for 1–2 days following the onset of the recovery phase, possibly because of the disturbance dynamo electric fields that can persist for several days. These results provide new insights into EPB morphology during the ascending and maximum phases of Solar Cycle 25 in Southeast Asia and highlight the critical role of the timing and evolution of geomagnetic storms in EPB development.