Multi-observation and Data Assimilation Analysis of 3-D Ionospheric Electron Density Variations During the Recovery Phase of the Gannon Storm

Equatorial electrodynamic processes in the ionosphere are inherently complex and highly variable, particularly during super geomagnetic storms. And accurate 3-D imaging of ionospheric variations and their temporal evolution remains a longstanding challenge in space weather research. At 2100 UT on May 11, 2024, multi-scale electron density variations were observed by Swarm A/C satellites over Australia.  On one hand, Swarm observations revealed prominent conjugate electron density enhancements, which was a phenomenon seldom reported in the early morning hours. On the other hand, observations from the Tianmu GNSS radio occultation (RO) indicated that the ionospheric F-region in the conjugate Southern Hemisphere was uplifted by more than 80 km over Australia and provided the evidence of the co-existence of equatorial plasma bubbles (EPBs). To better understand the physical mechanisms of these structures, we reconstructed their three-dimensional electron density distribution with NEDAM for the first time. The results reveal field-aligned characteristics in the enhancements. This suggests the presence of a dawn-side equatorial ionization anomaly (EIA). Using Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM) simulations, we further demonstrated that the formation of a dawn‐side EIA can be driven by the disturbance dynamo electric field. The co‐existence of the dawn‐side EIA and embedded EPBs gave rise to the observed multi‐peak electron density structures.