FeO emission in the mesosphere: Detectability, diurnal behavior, and modeling

There continue to be surprises in the identification of the terrestrial nightglow components. Comparison of the nightglow as measured in astronomical sky spectra and Optical Spectrograph and Infrared Imager System (OSIRIS)/Odin orbiter data with that on FeO emission in meteor trains and laboratory experiments demonstrates that this emission is an important part of the nightglow, appearing as a quasi-continuum between 540 and 680 nm, with maximum intensity at 595 nm. In order to study the FeO emission, account must be taken of other nearby emissions, including the 589 nm sodium emission lines, and the underlying 8-2 OH Meinel band. The temporal behavior of the three emissions is normally closely related, but strong excursions can occur, which could provide valuable information on atmospheric processes. The temporal behavior of the FeO and OH emissions was compared to model results from the one-dimensional and time-resolved model FeMOD, which describes the iron chemistry in the mesosphere/lower thermosphere. Further observations and comparisons with satellite and lidar data as well as models will make it possible to improve our understanding of mesospheric chemistry, meteor ablation, and the role of iron in the atmosphere.