Search

Here we compare the global‐scale morphology of Earth's the Far‐Ultraviolet (FUV) emissions observed by NASA's Global‐scale Observations of Limb and Disk (GOLD) mission to those modeled using the Global Airglow (GLOW) code with atmospheric parameters provided by Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM). The O 5S oxygen (135.6 nm) and N2 Lyman‐Birge‐Hopfield (LBH) emissions are observed over the Western hemisphere every 30 min by the GOLD instrument. The FUV brightness of the thermosphere‐ionosphere is expected to vary in systemic ways with respect to geophysical parameters, solar energy input from above, and terrestrial weather input from below. In this paper we examine the O 5S oxygen emission and the N2 LBH emission brightnesses with local time, latitude, season, tides, geomagnetic activity, and solar activity based on GOLD observations and GLOW modeling. Early GOLD observations indicate that the model effectively reproduces the brightness variations with local time and latitude but is biased low in magnitude. However, the TIEGCM is unable to accurately represent the extraordinary nighttime equatorial ionization anomaly observed by GOLD. It is also expected from these results that the signal from geomagnetic storms may obscure tidal signals. Plain Language Summary: In January 2018, a FUV instrument, the Global‐scale Observations of Limb and Disk (GOLD), was launched as a NASA mission of opportunity aboard a geostationary satellite and scientific operations began in October of 2018. GOLD views the entire disk of the Earth every 30 min, allowing the separation of geophysical variability in both space and time. This allows an unprecedented test of global models. Here, we model the Earth's upper atmosphere using the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIEGCM), which produces temperature and the densities of the major chemical components of the neutral atmosphere, ionized plasma densities, and neutral air temperatures. These atmospheric temperatures and densities are used to calculate the Earth's upper atmosphere emissions in the Far‐Ultraviolet (FUV) with the Global Airglow (GLOW) model. The calculated emission rates are then used to compute the expected FUV signals as observed from geostationary orbit. In this paper, we show how the FUV brightness varies with local time, season, atmospheric activity, and solar activity. Of particular interest is that the GLOW model excels at producing FUV brightnesses that match the local time and latitude trends of the daytime observations; however, the model fails to adequately portray the extraordinary nighttime phenomena observed by GOLD. Key Points: The Global‐scale Observations of Limb and Disk (GOLD) instrument observes the Earth in the Far‐Ultraviolet (FUV) from a geostationary orbitGLOW adequately calculates the FUV brightness for various local times, latitudes, solar forcing, and lower atmospheric forcingGLOW calculations indicate the oxygen brightness varies by ±45 R and the effective temperature varies by more than 80 K due to tides [ABSTRACT FROM AUTHOR]