Measuring FeO variation using astronomical spectroscopic observations
Stefanie Unterguggenberger1, Stefan Noll1, Wuhu Feng2,3, John M. C. Plane2, Wolfgang Kausch4,1, Stefan Kimeswenger5,1, Amy Jones6,1, and Sabine Moehler71Institut für Astro- und Teilchenpyhsik, Universität Innsbruck, Technikerstr. 25/8, 6020 Innsbruck, Austria 2School of Chemistry, University of Leeds, Woodhouse Lane, Leed LS 9JT, United Kingdom 3National Centre for Atmospheric Science, University of Leeds, Woodhouse Lane, Leed LS 9JT, United Kingdom 4Institute for Astrophysics, University of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria 5Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta, Chile 6Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany 7European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
Received: 21 Jul 2016 – Accepted for review: 18 Oct 2016 – Discussion started: 18 Oct 2016
Abstract. Airglow emission lines of OH, O2, O and Na are commonly used to probe the MLT (mesosphere/lower thermosphere) region of the atmosphere. Furthermore, molecules like electronically excited NO, NiO and FeO emit a (pseudo-) continuum. These continua are harder to investigate than atomic emission lines. So far, limb-sounding from space and a small number of ground-based low-to-medium resolution spectra have been used to measure FeO emission in the MLT. In this study the medium-to-high resolution echelle spectrograph X-shooter at the Very Large Telescope (VLT) in the Chilean Atacama desert (24°37' S, 70°24' W, 2635 m) is used to study the FeO pseudo-continuum in the range from 0.5 to 0.72 μm based on 3662 spectra. Variations of the FeO spectrum itself, as well as the diurnal and seasonal behaviour of the FeO and Na emission intensities are reported. These airglow emissions are linked by their common origin, meteoric ablation, and share O3 as a common reactant. Major differences are found in the main emission peak of the FeO airglow spectrum between 0.58 and 0.61 μm, compared with a theoretical spectrum. The FeO and Na airglow intensities exhibit a similar nocturnal variation, and a semi-annual seasonal variation with equinoctial maxima. This is satisfactorily reproduced by a whole atmosphere chemistry climate model, if the quantum yields for the reactions of Fe and Na with O3 are 13 ± 3 % and 11 ± 2 %, respectively. However, a comparison between the modelled O3 in the upper mesosphere and measurements of O3 made with the SABER satellite instrument suggests that these quantum yields may be a factor of ∼ 2 smaller.
Unterguggenberger, S., Noll, S., Feng, W., Plane, J. M. C., Kausch, W., Kimeswenger, S., Jones, A., and Moehler, S.: Measuring FeO variation using astronomical spectroscopic observations, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-661, in review, 2016.