Long‐Lived Equatorial Plasma Bubbles Persisting Into the Afternoon Over the Pacific Sector During the Recovery Phase of the April 2023 Geomagnetic Storm

Equatorial plasma bubbles (EPBs) are typically nighttime ionospheric irregularities, and their persistence into daytime sectors remains insufficiently understood. Here, we investigate long‐lived EPB‐related plasma depletion structures over the Pacific sector during the recovery phase of the 23–25 April 2023 geomagnetic storm using Formosa Satellite‐7/Constellation Observing System for Meteorology, Ionosphere, and Climate‐2 (FORMOSAT‐7/COSMIC‐2) in situ ion density, Swarm‐B electron density, ground‐based Global Navigation Satellite System (GNSS) rate of total electron content index (ROTI), COSMIC‐2 Global Ionospheric Specification (GIS) electron density, and Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) atomic oxygen‐to‐molecular nitrogen column density ratio (O/N 2 ) observations. COSMIC‐2 observations show that depletion signatures increased on 24 April, persisted from post‐sunrise through local noon, and remained identifiable in the afternoon during 0–6 Universal Time (UT) on 25 April, corresponding to an observable persistence interval of about 20 hr. Consecutive along‐track density profiles reveal that the structures gradually weakened from clear depletions into faint residual signatures while remaining within similar longitude ranges. Ground‐based ROTI observations provide independent evidence for sustained EPB‐related irregularities from the postmidnight sector to local noon at the Northern Hemisphere stations and a weaker but longer‐lasting response extending into the afternoon at the American Samoa Power Authority (ASPA) station in the Southern Hemisphere. Swarm‐B independently detected a morning super plasma depletion extending to ∼35° magnetic latitude in the Southern Hemisphere, corresponding to an apex altitude exceeding ∼3,500 km. COSMIC‐2 GIS data show enhanced postmidnight low‐latitude topside electron density followed by reduced low‐to‐middle latitude background density after sunrise, while GUVI O/N 2 observations indicate a hemispherically asymmetric thermospheric composition response. These observations suggest that the daytime signatures were weak residual traces of storm‐time nighttime/postmidnight EPBs rather than newly generated daytime irregularities. High‐apex field‐aligned depletion structure and reduced post‐sunrise background plasma density likely slowed refilling, enabling residual EPB‐related structures to persist into unusually late local‐time sectors.