This paper presents observations of upper atmospheric vortices following two geomagnetic storms: a Kp 9− storm on 10 October 2024 and a Kp 8+ storm occurring in April of 2023. These observations, using neutral composition and effective neutral temperatures from the NASA GOLD mission, reveal vortices similar to those initially reported by Evans, Correira, et al. (2024, https://doi.org/10.1029/2024GL110506 ) for the historic geomagnetic storm of May 2024. Development of vortices following more typical geomagnetic storms demonstrate that such vortices are not as rare as was originally speculated. For all three storms, vortices appeared in GOLD data following similar elapsed times after storm onset and developed in the Southern Hemisphere at similar locations. The size of the vortices varied for the three storms, as did whether or not a vortex appeared in the Northern Hemisphere.

After days of intense solar activity, active region AR3664 launched seven CMEs towards Earth producing an extreme G5 geomagnetic storm commencing at 16:45 UT on Saturday May 10, 2024. The storm impacted power grids, disrupted precision navigational systems used by farming equipment, and generated aurora seen around the globe. The storm produced remarkable effects on composition, temperature, and dynamics in the Earth’s thermosphere that were observed by NASA’s Global-scale Observations of the Limb and Disk (GOLD) mission and are reported here for the first time. We use synoptic disk images of ΣO/N2 and neutral temperature (at ~160 km) measured by GOLD to directly link dynamics resulting from the storm with dramatic changes in thermospheric composition and temperature. We observe an apparent rotation simultaneously in ΣO/N2, neutral temperature, and total electron content. Equator-to-pole temperature differences reach 400 K with peak neutral temperatures near 160 km exceeding 1400 K at high latitudes.

After days of intense solar activity, active region AR3664 launched seven CMEs toward Earth producing an extreme G5 geomagnetic storm commencing at 17:05 UT on 10 May 2024. The storm impacted power grids, disrupted precision navigational systems used by farming equipment, and generated aurora seen around the globe. The storm produced remarkable effects on composition, temperature, and dynamics in the Earth's thermosphere that were observed by NASA's Global-scale Observations of the Limb and Disk (GOLD) mission and are reported here for the first time. We use synoptic disk images of Sigma O/N2 and neutral temperature (at similar to 160 km) measured by GOLD to directly link dynamics resulting from the storm with dramatic changes in thermospheric composition and temperature. We observe a heretofore unseen spatial morphology simultaneously in Sigma O/N2, neutral temperature, and total electron content. Equator-to-pole temperature differences reach 400 K with high latitude peak neutral temperatures near 160 km exceeding 1400 K. On Saturday 10 May 2024, the sun launched a wave of energized plasma toward the Earth. A large disturbance in the Earth's magnetic field associated with the solar wind resulted in an extreme geomagnetic storm. The storm impacted power grids, disrupted navigational systems used by farming equipment, and produced aurora seen around the globe. The storm produced remarkable effects in the Earth's upper atmosphere that were observed by NASA's Global-scale Observations of the Limb and Disk (GOLD) mission. In this letter, we use images measured by GOLD to directly link atmospheric dynamics resulting from the May 10-12 superstorm with dramatic changes in composition, temperature, and global circulation in the Earth's upper atmosphere. We observe previously unseen structure in the upper atmosphere associated with equator-to-pole temperature differences exceeding 400 K. Peak neutral temperatures near 160 km exceed 1400 K at high latitudes. GOLD disk images of Sigma O/N2 and neutral temperature link storm time dynamics with changes in thermospheric composition and temperature We observe a previously unseen spatial morphology in Sigma O/N2, neutral temperature, and total electron content Peak equator-to-pole temperature differences exceed 400 K but relax to pre-storm conditions well before Sigma O/N2

Observations of far‐ultraviolet (FUV) dayglow by the Global‐scale Observations of Limb and Disk (GOLD) mission provide an opportunity for quantifying the global‐scale response of the thermosphere to solar extreme‐ultraviolet variability and geomagnetic activity. Relative temperature changes can be measured by monitoring changes in the rotational structure observed in molecular nitrogen Lyman‐Birge‐Hopfield (LBH) band emissions. We present a new technique for deriving effective neutral temperatures from GOLD FUV observations using optimal estimation fits to spectra containing LBH band emissions. We provide an overview of the theoretical basis for the GOLD Level 2 TDISK algorithm. Effects on derived effective neutral temperatures from instrument artifacts and particle background are reviewed. We also discuss GOLD Level 1C DAY and Level 2 TDISK data products and present representative examples of each. We show that effective neutral temperatures vary with local time, exhibit a strong dependence on season and solar zenith angle, and correlate strongly with geomagnetic and solar activity. Finally, we present results from a preliminary data product validation that show good agreement with coincident GOLD exospheric temperatures and predictions from a global reference atmospheric model.

Observations of far‐ultraviolet (FUV) dayglow by the Global‐scale Observations of Limb and Disk (GOLD) mission provide a new opportunity to monitor relative composition changes in the upper atmosphere as well as solar extreme ultraviolet (EUV) variability. Relative composition changes are quantified by ΣO/N 2 , the column density ratio of atomic oxygen to molecular nitrogen, while Q EUV provides a measure of the solar EUV energy flux from 1 to 45 nm into the upper atmosphere. This spectral range provides the ionizing radiation which ultimately results in FUV airglow emission produced by photodissociation and photoelectron impact. The quantities ΣO/N 2 and Q EUV are derived from GOLD FUV observations through lookup tables that are constructed using a first‐principles photoelectron transport model. The two FUV emissions used are O I 135.6 nm and the N 2 Lyman‐Birge‐Hopfield (LBH) bands. We present an overview of the theoretical basis for the algorithms and practical considerations for application to GOLD data. The effects of uncertainties in electron impact cross sections, off‐nadir viewing, and instrument artifacts are reviewed. We also discuss GOLD Level 1C DAY, Level 2 data products ON2 and QEUV, and present representative samples of each.

The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission has flown an ultraviolet‐imaging spectrograph on SES‐14, a communications satellite in geostationary orbit at 47.5°W longitude. That instrument observes the Earth's far ultraviolet (FUV) airglow at ~134–162 nm using two identical channels. The observations performed include limb scans, stellar occultations, and images of the sunlit and nightside disk from 6:10 to 00:40 universal time each day. Initial analyses reveal interesting and unexpected results as well as the potential for further studies of the Earth's thermosphere‐ionosphere system and its responses to solar‐geomagnetic forcing and atmospheric dynamics. Thermospheric composition ratios for major constituents, O and N2, temperatures near 160 km, and exospheric temperatures are retrieved from the daytime observations. Molecular oxygen (O2) densities are measured using stellar occultations. At night, emission from radiative recombination in the ionospheric F region is used to quantify ionospheric density variations in the equatorial ionization anomaly (EIA). Regions of depleted F region electron density are frequently evident, even during the current solar minimum. These depletions are caused by the “plasma fountain effect” and are associated with the instabilities, scintillations, or “spread F” seen in other types of observations, and GOLD makes unique observations for their study.

The Global-scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs an instrument with two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Societe Europeenne des Satellites (SES) and located in geostationary orbit at 47.5 degrees west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N-2 Lyman-Birge-Hopfield (LBH) 137-162 nm radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here, we provide an overview of the instrument and compare its prelaunch and early flight measurement performance. Direct comparison of LBH spectra of an electron lamp taken before launch with spectra on orbit provides evidence that both cascade and direct excitation are important sources of thermospheric LBH emission. Plain Language Summary The Global-scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating tides on time scales as short as 30 min. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by SES and located in geostationary orbit at 47.5 degrees west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N-2 LBH radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here we describe the GOLD instrument including its optical system and detector. Its performance was characterized in the lab before launch. We compare measurements of laboratory sources made then to observations of the thermosphere after launch and find good agreement.

The Global-scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Societe Europeenne des Satellites (SES) and located in geostationary orbit at 47.5 degrees west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N-2 Lyman-Birge-Hopfield radiances from the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here we describe the algorithms and science data processing that convert downlinked data to spectral-spatial image cubes and occultation spectra, calibrated in geophysical units. These Level 1 data products include disk and near-equatorial limb images of spectra acquired on a 30-min cadence beginning at 06:10 Coordinated Universal Time and ending at 23:10. Nighttime images of the disk, covering regions east of the terminator, begin at 20:10 Coordinated Universal Time and also continue until 00:40 the next day. During the day, some limb images are replaced by time series of stellar spectra that exhibit absorption by molecular oxygen as the star is occulted by the Earth's atmosphere. Instrumental artifacts that occasionally appear in the released data are discussed. Plain Language Summary The Global-scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere-thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Societe Europeenne des Satellites (SES) and located in geostationary orbit at 47.5 degrees west longitude (near the mouth of the Amazon River). They make images of the entire disk that is observable from geostationary orbit and of the near-equatorial limb using ultraviolet emissions by atomic oxygen and molecular nitrogen. They also observe occultations of stars to measure molecular oxygen column densities on the limb. These observations are used to produce Level 1 data products that consist of geophysically calibrated spectral-spatial image cubes of radiances on the disk and limb and time series of stellar occultation spectra. Here we describe the algorithms and data processing used to produce these products and provide examples of them. We also present examples of instrumental artifacts that occasionally appear in some products. Key Points GOLD makes images of OI 135.6 nm and N-2 LBH radiances emitted by the ionosphere-thermosphere and observes absorption by O-2 on the limb The algorithms and data processing that produce geophysically calibrated Level 1 data products from these observations are described Artifacts observed in some of the Level 1 data products are discussed

Surface scatter of electromagnetic radiation is not caused directly by surface roughness, but rather by the effect of the phase variation induced on the transmitted or reflected wavefront as it propagates; i.e., surface scatter is a diffraction phenomenon caused directly by the propagation process. The scatter behavior is thus strongly affected by: (1) the statistical nature of the surface, (2) the propagating wavelength, (3) the angle of incidence, and (4) the refractive index of the media both before and after the interface of the surface encountered.

The Earth's thermosphere and ionosphere constitute a dynamic system that varies daily in response to energy inputs from above and from below. This system can exhibit a significant response within an hour to changes in those inputs, as plasma and fluid processes compete to control its temperature, composition, and structure. Within this system, short wavelength solar radiation and charged particles from the magnetosphere deposit energy, and waves propagating from the lower atmosphere dissipate. Understanding the global-scale response of the thermosphere-ionosphere (T-I) system to these drivers is essential to advancing our physical understanding of coupling between the space environment and the Earth's atmosphere. Previous missions have successfully determined how the "climate" of the T-I system responds. The Global-scale Observations of the Limb and Disk (GOLD) mission will determine how the "weather" of the T-I responds, taking the next step in understanding the coupling between the space environment and the Earth's atmosphere. Operating in geostationary orbit, the GOLD imaging spectrograph will measure the Earth's emissions from 132 to 162 nm. These measurements will be used image two critical variables-thermospheric temperature and composition, near 160 km-on the dayside disk at half-hour time scales. At night they will be used to image the evolution of the low latitude ionosphere in the same regions that were observed earlier during the day. Due to the geostationary orbit being used the mission observes the same hemisphere repeatedly, allowing the unambiguous separation of spatial and temporal variability over the Americas.