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Abstract The Global‐scale Observations of Limb and Disk (GOLD) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments were used to investigate the thermospheric composition and temperature responses to the geomagnetic storm on 23–24 April, 2023. Global‐scale Observations of Limb and Disk observed a faster recovery of thermospheric column density ratio of O to N₂(ΣO/N₂) in the southern hemisphere (SH) after the storm ended at 12 Universal time (UT) on 24 April. After 12 UT on 25 April, ΣO/N₂had mostly recovered in both hemispheres. Global‐scale Observations of Limb and Disk also observed an increase of middle thermospheric temperature (140–200 km) (Tdisk) on 24 April with a maximum of 340 K. Within 4–6 hr of the storm ending on 24 April, Tdisk enhancement persisted between 30°N and 60°N, 100°W and 30°W, while Tdisk lower than pre‐storm quiet day (17 April) was observed between 45°W and 15°W, 40°S and 50°N. Tdisk recovered between 100°W and 45°W, 30°N and 55°S. On 25 April, Tdisk was lower than on 17 April across the entire GOLD Field‐of‐Regard (FOR) by ∼50–110 K. Additionally, solar irradiance decreased by 15%–20% from 17 to 25 April, indicating that the lower Tdisk on 25 April resulted from both storm and solar irradiance variations. Latitudinal variations of Tdisk and the SABER observed Nitric Oxide (NO) cooling rate revealed that NO cooling is crucial for the lower Tdisk in the northern hemisphere (NH) mid‐high latitudes on 25 April. These results provide direct evidence of decreased thermospheric temperature during storm recovery phase than pre‐storm quiet times. 

Abstract We report a new ionosphere phenomenon: Equatorial ionization anomaly (EIA) discontinuity (EIAD), based on OI 135.6 nm radiance observations from the Global Observations of Limb and Disk (GOLD), ground‐based total electron content maps and in‐situ ion density data from Constellation Observing System for Meteorology, Ionosphere, and Climate‐2. The EIAD occurs when the OI radiance of the EIA crest has a local minimum, at a fixed UT, with the radiance in the local longitude region being weaker than that on the east and west sides. In the GOLD field‐of‐view, EIAD follows the seasonal variations of EIA. EIAD appears more often over the Atlantic Ocean and Africa than over South America. It occurs more in the southern crest during the December solstice, and more in the northern crest during both equinoxes. EIAD can occur under both quiet and disturbed times. 

Abstract This study develops a new Bubble Index to quantify the intensity of 2‐D postsunset equatorial plasma bubbles (EPBs) in the American/Atlantic sector, using Global‐scale Observations of the Limb and Disk (GOLD) nighttime data. A climatology and day‐to‐day variability analysis of EPBs is conducted based on the newly‐derived Bubble Index with the following results: (a) EPBs show considerable seasonal and solar activity dependence, with stronger (weaker) intensity around December (June) solstice and high (low) solar activity years. (b) EPBs exhibit opposite geomagnetic activity dependencies during different storm phases: EPBs are intensified concurrently with an increasing Kp, but are suppressed with high Kp occurring 3–6 hr earlier. (c) For the first time, we found that EPBs' day‐to‐day variation exhibited quasi‐3‐day and quasi‐6‐day periods. A coordinated analysis of Ionospheric Connection Explorer (ICON) winds and ionosonde data suggests that this multi‐day periodicity was related to the planetary wave modulation through the wind‐driven dynamo. 

Abstract The geomagnetic storm on February 3, 2022 caused the loss of 38 Starlink satellites of Space‐X. The Global‐scale Observations of the Limb and Disk (GOLD) observations and Multi‐Scale Atmosphere Geospace Environment (MAGE) model simulations are utilized to investigate the thermospheric composition responses to the Space‐X storm. The percentage difference of the GOLD observed thermospheric O and N₂column density ratio (∑O/N₂) between the storm time (February 3, Day‐of‐Year [DOY] 34) and quiet time (DOY 32) shows a depletion region in the local noon sector mid‐high latitudes in the southern hemisphere, which corresponds to the east side of GOLD field‐of‐view (FOV). This is different from the classic theory of thermospheric composition disturbance during geomagnetic storms, under which the ∑O/N₂depletion is usually generated at local midnight and high latitudes, and thus, appear on the west side of GOLD FOV. MAGE simulations reproduce the observations qualitatively and indicate that the ∑O/N₂depletion is formed due to strong upwelling in the local morning caused by strong Joule heating. Interestingly, enhanced equatorward winds appear near local midnight, but also in the local morning sector, which transports ∑O/N₂depletion equatorward. The depletion corotates toward the local afternoon and is observed in the GOLD FOV. The equatorward winds in the local morning are due to the ion‐neutral coupling under the conditions of a dominant positive interplanetary magnetic field east‐west component (B_y) during the storm.