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Using NASA's Global‐scale Observations of the Limb and Disk (GOLD) imager, we report nightside ionospheric changes during the G5 super geomagnetic storm of 10 and 11 May 2024. Specifically, the nightside southern crest of the Equatorial Ionization Anomaly (EIA) was observed to merge with the aurora near the southern tip of South America. During the storm, the EIA southern crest was seen moving poleward as fast as 450 m/s. Furthermore, the aurora extended to mid‐latitudes reaching the southern tips of Africa and South America. The poleward shift of the equatorial ionospheric structure and equatorward motion of the aurora means there was no mid‐latitude ionosphere in this region. These observations offer unique insights into the ionospheric response to extreme geomagnetic disturbances, highlighting the complex interplay between solar activity and Earth's upper atmosphere. Plain Language Summary: On Earth's nightside during the super geomagnetic storm that occurred on 10 May 2024, NASA's GOLD imager saw something new: a part of Earth's ionosphere, the southern peak of what typically appears as a double‐peaked structure in the ionospheric density at equatorial and low latitudes, merged with the aurora near the southern tip of South America. This has never been reported before. Additionally, the boundary of the aurora expanded further equatorward than usual. These observations of what happened in the Earth's ionosphere during this super storm are reported for the first time in this study. Key Points: EIA crests between ∼70° and 35°W moved poleward, with northern and southern crest reaching ∼38°N and ∼35°S Mlat in the American sectorSouthern EIA crest moved poleward with a speed of ∼450 m/s near ∼55°W Glon during strong IMF Bz and d(Dst)/dtFirst observation of the merging of an EIA crest with the aurora indicating no mid‐latitude ionosphere [ABSTRACT FROM AUTHOR]

A coronal mass ejection erupted from the Sun on 21 April 2023 and created a G4 geomagnetic storm on 23 April. NASA's global‐scale observations of the limb and disk (GOLD) imager observed bright equatorial ionization anomaly (EIA) crests at ∼25° Mlat, ∼11° poleward from their average locations, computed by averaging the EIA crests during the previous geomagnetic quiet days (18–22 April) between ∼15°W and 5°W Glon. Reversed C‐shape equatorial plasma bubbles (EPBs) were observed reaching ∼±36° Mlat (∼40°N and ∼30°S Glat) with apex altitudes ∼4,000 km and large westward tilts of ∼52°. Using GOLD's observations EPBs zonal motions are derived. It is observed that the EPBs zonal velocities are eastward near the equator and westward at mid‐latitudes. Model‐predicted prompt penetration electric fields indicate that they may have affected the postsunset pre‐reversal enhancement at equatorial latitudes. Zonal ion drifts from a defense meteorological satellite program satellite suggest that westward neutral winds and perturbed westward ion drifts over mid‐latitudes contributed to the observed latitudinal shear in zonal drifts. Plain Language Summary: A severe geomagnetic storm occurred on 23 April 2023. The effects of the storm on the nighttime equatorial and mid‐latitude ionosphere are investigated using NASA's global‐scale observations of the limb and disk (GOLD) measurements. GOLD observed bright, widely separated equatorial ionization anomaly (EIA) crests between ∼15°W and 5°W Glon. Extreme equatorial plasma bubbles (EPBs) reaching mid latitudes at ∼40 N and ∼30°S Glat with apex altitudes of ∼4,000 km at the magnetic equator were observed over these longitudes. The EPBs velocities were eastward at low latitudes, between the EIA crests, and reversed to westward near mid‐latitudes. At mid‐latitudes EPBs showed westward tilts that were larger than previous observations during similar geomagnetic conditions. Key Points: Maximum poleward shift (∼11°) of equatorial ionization anomaly crests was observed between ∼15°W and 5°W GlonReversed C‐shape Equatorial Plasma Bubbles (EPBs) extended to ∼±36° Mlat (∼40°N and ∼30°S Glat) with apex altitudes reaching ∼4,000 kmShear in EPBs zonal drifts is formulated as a function of magnetic apex heights based on their tilts [ABSTRACT FROM AUTHOR]

The Global-scale Observation of Limb and Disk (GOLD) mission, for the first time, provides synoptic two-dimensional (2D) maps of OI 135.6 nm observations. These maps describe the unambiguous and dynamic evolution of nighttime ionospheric F2-peak electron densities (NmF2) as the 135.6 nm airglow emission radiance correlates well with NmF2 at night. On November 19, 2018, the 135.6 nm radiance measured by GOLD, NmF2 measured by a digisonde, and GPS total electron content (TEC) measurements at Cachoeira Paulista (CP) all showed a postsunset enhancement, with an increase near 22:30 universal time. The 135.6 nm radiance map showed that this enhancement was due to the southward movement of the southern equatorial ionization anomaly (EIA) crest. Therefore, the GOLD observation showed the linkage between postsunset enhancement of NmF2 and EIA movement. Furthermore, unlike the southward movement of the southern crest, the corresponding EIA northern crest, however, did not show northward motion. This is the first time that the EIA hemispheric asymmetry, which included both different densities and movement of two crests in a short time period (<2-h), was captured. The cause of this asymmetric movement of the two crests is not clear and requires further investigation. [ABSTRACT FROM AUTHOR]

In March 2014 an all-sky imager (ASI) was installed at the Jicamarca Radio Observatory (11.95° S, 76.87°W; 0.3° S MLAT). We present results of equatorial spread F (ESF) characteristics observed at Jicamarca and at low latitudes. Optical 6300 and 7774Å airglow observations from the Jicamarca ASI are compared with other collocated instruments and with ASIs at El Leoncito, Argentina (31.8° S, 69.3°W; 19.8° S MLAT), and Villa de Leyva, Colombia (5.6° N, 73.52°W; 16.4° N MLAT). We use Jicamarca radar data, in incoherent and coherent modes, to obtain plasma parameters and detect echoes from irregularities. We find that ESF depletions tend to appear in groups with a group-to-group separation around 400-500 km and withingroup separation around 50-100 km. We combine data from the three ASIs to investigate the conditions at Jicamarca that could lead to the development of high-altitude, or topside, plumes. We compare zonal winds, obtained from a Fabry- Pérot interferometer, with plasma drifts inferred from the zonal motion of plasma depletions. In addition to the ESF studies we also investigate the midnight temperature maximum and its effects at higher latitudes, visible as a brightness wave at El Leoncito. The ASI at Jicamarca along with collocated and low-latitude instruments provide a clear twodimensional view of spatial and temporal evolution of ionospheric phenomena at equatorial and low latitudes that helps to explain the dynamics and evolution of equatorial ionospheric/thermospheric processes. [ABSTRACT FROM AUTHOR]