Error Analysis of O+ Density Retrieved from Combined 83.4 nm and 61.7 nm EUV dayglow

Abstract:

One of the brightest features of Earth's EUV dayglow is the OII 83.4 nm line, which is excited by solar EUV/XUV photons and photoelectron flux. The emission is optically thick and resonantly scatters off of O+ ions in the F2 region of the ionosphere. Given neutral densities and the emission source, a limb scan of OII 83.4 nm intensity can be inverted to retrieve the underlying O+ density. The optically thin OII 61.7 nm emission is excited by the same mechanism and can serve as a proxy for the 83.4 nm source, but the two are not perfectly correlated due to their different absorption cross sections. We apply Bayesian analysis and a statistical model of the multiple scattering to investigate how uncertainties in 61.7 nm measurements, neutral densities and cross sections, and scattering cross sections affect uncertainty in retrieved O+ densities for Chapman ionosphere.