Merging and Dissipation of Intense Equatorial Plasma Bubbles With Large‐Scale Mid‐Latitude Low Electron Density Regions During the 23–24 April 2023 Geomagnetic Storm

Abstract The extension of the post‐sunset equatorial plasma bubbles (EPBs) to mid‐latitudes during geomagnetic storms has been widely reported. However, previous research has primarily focused on the initiation and spatial distribution of these EPBs, while their decay processes remain underexplored. In this study, we provide observations of the evolution and dissipation of intense EPBs during the geomagnetic storm on 23–24 April 2023, using measurements from the Global‐scale Observations of the Limb and Disk (GOLD), Swarm, and COSMIC‐2 satellites. During the storm main phase, intense EPBs with zonal extents of ∼2–3° and latitudinal extents reaching up to ±35° magnetic latitude (Mlat) were observed between 15°W and 5°W. Simultaneously, very low electron density regions, spanning approximately from ±30° to ±45° Mlat and 420–500 km in altitude, were observed in the mid‐latitudes. During the storm, the EPBs were observed to extend gradually poleward and subsequently encountered the low electron density regions. This encounter process, along with the storm‐caused electric field dynamics, led to a gradual weakening and diffusion of the EPBs. The airglow images from GOLD showed that EPBs evolved from coherent depletions into structurally diffused forms with embedded filamentary features and eventually merged into the background. Notably, a hemispheric asymmetry in EPB dissipation was observed. In the Northern Hemisphere, EPBs tended to retain their morphology for a longer time, while in the Southern Hemisphere, more rapid dissipation occurred, likely due to differing background plasma conditions and magnetic field configurations in the two hemispheres. These findings reveal a previously uncharacterized feature of EPB dissipation during geomagnetic storms.