Ionospheric Disturbances Detection Based on BDS‐GEO Observations With Prophet Model Over China: A Case Study of May 2017 Geomagnetic Storm.

We investigate ionospheric disturbances over China during the May 2017 geomagnetic storm using an integrated data set, including total electron content (TEC) measurements from BeiDou Navigation Satellite System's (BDS) Geostationary Earth Orbit (GEO) observations, ionosonde data, Swarm satellites, and global navigation satellite system (GNSS) radio occultation (RO) data. TEC anomalies were identified using the Prophet forecasting model, and results were compared with three sliding time window methods, showing consistent outcomes. The significant TEC increase during the storm's main phase was driven by prompt penetration electric fields (PPEF) linked to interplanetary magnetic field (IMF) Bz fluctuations. During the recovery phase, TEC increased on May 29 night, associated with southward IMF Bz turning and westward PPEF. Notably, the TEC negative storm observed at the KUN1 station on the morning of May 29 was likely caused by F‐layer uplift driven by the eastward overshielding electric field (OPEF) during the recovery phase, which induced Rayleigh‐Taylor instability and resulted in the formation of plasma bubbles. Additionally, the electron density (Ne) measured by COSMIC and Swarm satellites, along with ionospheric F2 layer parameters critical frequency (foF2) and peak height (hmF2) showed significant increases during the storm. A negative ionospheric response was observed over China on May 30 from 00:00 to 12:00 UT, likely caused by thermosphere composition changes. This study highlights the efficiency of BDS‐GEO satellites in monitoring ionospheric TEC variations, capturing spatiotemporal characteristics of disturbances, and validating the Prophet model for detecting anomalous TEC fluctuations during geomagnetic storms. Plain Language Summary: This study analyzes ionospheric disturbances over China during the May 2017 geomagnetic storm using the BeiDou Navigation Satellite System's (BDS) Geostationary Earth Orbit (GEO) observations, Swarm, and ionosonde data. The Prophet model detected TEC anomalies and showed that prompt penetration electric fields (PPEF) and interplanetary magnetic field (IMF) Bz fluctuations caused significant TEC increases during the storm's main phase. During the recovery phase, additional TEC increases were linked to the IMF Bz's southwest turn. A negative response on May 30 was likely due to thermospheric composition changes. The results highlight the efficiency of BDS‐GEO satellites and the Prophet model in monitoring ionospheric variations during geomagnetic storms. Key Points: The significant TEC increase investigated by BDS‐GEO was primarily driven by PPEF during the main phase of the geomagnetic stormThe Prophet model was used to detect ionospheric disturbances by BDS‐GEO observationsTwo positive and one negative ionospheric disturbances were noted during the storm in May 2017 [ABSTRACT FROM AUTHOR]