Towards a Decontaminated Thermospheric Column O/N2 Ratio using ICON Mission Data

The thermospheric column O/N2 ratio is a useful diagnostic of relative composition variations and is a powerful proxy of ionospheric electron density. It has been used to reveal the impact of thermospheric composition on the ionosphere during both quiet and storm times. The column O/N2 ratio is inferred from the ratio of observed emission intensities of atomic oxygen emissions at 135.6 nm and molecular nitrogen emissions at Lyman-Birge Hopfield band wavelengths in far ultraviolet dayglow imaged by space-based instruments. Retrieval algorithms assume that these emissions are produced by photoelectron impact. However, a non-negligible contribution to atomic oxygen emissions from O+ radiative recombination in the ionosphere is ignored, resulting in contamination of the inferred column O/N2 ratio. In this work, we present progress towards decontaminating the column disk O/N2 ratio observed by the Far Ultraviolet Imaging Spectrograph onboard the Ionospheric Connection Explorer (ICON) between 2019 and 2022. Implications for interpreting thermosphere-ionosphere tidal coupling using the column O/N2 ratio will be discussed.