An Approach to Determine O and N2 Densities in the Thermosphere Using EUV Airglow

This memorandum documents the development and validation of an algorithm designed to retrieve thermospheric atomic oxygen (O) andmolecular nitrogen (N2) densities over the altitude range 150-400 km using measurements of extreme ultraviolet (EUV) dayglow from theIonospheric Connection Explorer (ICON). This measurement approach does not have an inherent ionospheric emission that can, under certainconditions, complicate the analysis and interpretation of these measurables using state-of-the-art far-ultraviolet (FUV) airglow measurementapproach. Also, since EUV airglow emissions are produced directly by solar extreme ultraviolet rather than by the secondary process of impactby the correspondingly generated photoelectrons, this method has the potential to enable expansion of neutral density observations into theauroral zone and polar cap where the FUV measurement cannot be applied. These first results are validated by comparison to the MSIS 2.0model, as well as contemporaneous composition and neutral density measurements from the NASA GOLD and Swarm missions. Areas forfuture development and improvement in the measurement and analysis of these emissions are also discussed.