Immel, Thomas J.Eastes, Richard W.McClintock, William E.Mende, Steven B.Frey, Harald U.Triplett, Colin C.England, Scott L.2020-10-132020-10-132020-09-30Immel, T.J.; Eastes, R.W.; McClintock, W.E.; Mende, S.B.; Frey, H.U.; Triplett, C.; England, S.L. Daily Variability in the Terrestrial UV Airglow. Atmosphere 2020, 11, 1046.http://hdl.handle.net/10919/100469New capability for observing conditions in the upper atmosphere comes with the implementation of global ultraviolet (UV) imaging from geosynchronous orbit. Observed by the NASA GOLD mission, the emissions of atomic oxygen (OI) and molecular nitrogen (N<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula>) in the 133&ndash;168-nm range can be used to characterize the behavior of these major constituents of the thermosphere. Observations in the ultraviolet from the first 200 days of 2019 indicate that the oxygen emission at 135.6 nm varies much differently than the broader Lyman-Birge-Hopfield (LBH) emission of N<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula>. This is determined from monitoring the average instrument response from two roughly 1000 km<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mn>2</mn></msup></semantics></math></inline-formula> areas, well separated from one another, at the same time of each day. Variations in the GOLD response to UV emissions in the monitored regions are determined, both in absolute terms and relative to a running 7-day average of GOLD measurements. We find that variations in N<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> emissions in the two separate regions are significantly correlated, while oxygen emissions, observed in the same fixed geographic regions at the same universal time each day, exhibit a much lower correlation, and exhibit no correlation with the N<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> emissions in the same regions. This indicates that oxygen densities in the airglow-originating altitude range of 150&ndash;200 km vary independently from the variations in nitrogen, which are so well correlated across the dayside to suggest a direct connection to variation in solar extreme-UV flux. The relation of the atomic oxygen variations to solar and geomagnetic activity is also shown to be low, suggesting the existence of a regional source that modifies the production of atomic oxygen in the thermosphere.application/pdfenCreative Commons Attribution 4.0 Internationalairglowthermosphereatmospheric dynamicsArticle - Refereed2020-10-13https://doi.org/10.3390/atmos11101046