Quantifying the inversion accuracy of simplified physical models for the nighttime OI 135.6 nm emission

A comprehensive statistical analysis is performed to investigate the effects of plasma and neutral density variability on the OI 135.6 nm emission in the nighttime ionosphere. Typical and extreme cases obtained from climatological models are incorporated into a radiative transfer model recently developed by Qin et al. (2015) to systematically quantify the production and loss of the nighttime 135.6 nm emission, as well as to understand their dependence on the ionospheric and thermospheric conditions. It is shown that mutual neutralization can contribute ∼8%–40% of the 135.6 nm emission. Radiative transfer effects due to scattering and absorption reduce the peak brightness measured from a satellite platform in the limb direction by ∼0.3% to 22%. The reduction is more significant for a larger observing zenith angle, typically by ∼45% for lines of sight that go through altitudes below ∼150 km. Furthermore, inversion results show that ignoring radiative transfer effects lead to a maximum ∼12% underestimation of the N_mF₂, while ignoring mutual neutralization leads to a maximum ∼30% overestimation of the N_mF₂. In the presence of measurement noise, the estimation accuracy decreases with a decreasing signal-to-noise ratio, and the errors introduced by simplified physical models lead to a significant bias in the inversion results.