Evaluation of ionospheric densities using coincident OII 83.4 nm airglow and the Millstone Hill radar

We test the utility of the OII 83.4nm emission feature as a measure of ionospheric parameters. Observed with the Remote Atmospheric and Ionospheric Detection System (RAIDS) Extreme Ultraviolet Spectrograph on the International Space Station (ISS), limb profiles of 83.4nm emissions are compared to predicted dayglow emission profiles from a theoretical model incorporating ground-based electron density profiles measured by the Millstone Hill radar and parameterized by a best-fit Chapman- function. Observations and models are compared for periods of conjunction between Millstone Hill and the RAIDS fields-of-view. These RAIDS observations show distinct differences in topside morphology between two days, 15 January and 10 March 2010, closely matching the forward model morphology and demonstrating that 83.4nm emission is sensitive to changes in the ionospheric density profile from the 340km altitude of the ISS during solar minimum. We find no significant difference between 83.4nm emission profiles modeled assuming a constant scale height Chapman-α best-fit to the ISR measurements and those assuming varying scale height.