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Spatio‐Temporal Structure of Far Ultraviolet Martian Dayglow Observed by EMM‐EMUS
Mars' ultraviolet dayglow has been used to study its upper atmosphere for over four decades. Identifying variations in emission features has provided information on composition, density, and temperature. The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission observes Mars&...
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Published in: | Geophysical research letters 2022-10, Vol.49 (19), p.n/a |
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Main Authors: | , , , , , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Mars' ultraviolet dayglow has been used to study its upper atmosphere for over four decades. Identifying variations in emission features has provided information on composition, density, and temperature. The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission observes Mars' dayglow at Far and Extreme UV wavelengths. Variations in disk emission features are studied, with a focus on O I 130.4, CO Fourth Positive Group and C I 156.1 nm. All show variations with local time (LT) and emission angle as expected. Dawn‐dusk asymmetry observed is attributed to LT differences in advection. Variations in the brightness of several dayglow features, including 130.4 nm, with irregular shapes are noted in around 25% of the disk images. These display some LT and hemispheric asymmetry in their occurrence rates. Examination of their spatial structure, occurrence, and spectra suggests these are associated with variations in composition and photoelectron flux.
Plain Language Summary
Measurements of ultraviolet light coming from Mars' upper atmosphere has been used to measure its properties. From the color and brightness of the light, it is possible to identify both what chemical species are present in this region, their temperature and other information. The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission makes observations of this ultraviolet light in wavelength regions described as far and extreme ultraviolet. This study looks at emissions of far ultraviolet light that correspond to oxygen atoms, carbon monoxide, and carbon dioxide molecules. The circulation of gases in the upper atmosphere results in a difference in the brightness of these emissions between dawn and dusk. This study also introduces observations of irregularly shaped bright patches in these emissions. The shape, location, and spectra of these suggest they are the result of changes in the chemical composition of the upper atmosphere.
Key Points
Variations in the ultraviolet dayglow from the Martian thermosphere with local time (LT) and emission viewing angle are characterized
Asymmetry in the dayglow between dawn and dusk varies by emission from +15.4% to −12.3% in response to transport and temperature
Patches of significant dayglow brightness increase are observed that appear to result from changes in composition and photoelectron flux |
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ISSN: | 0094-8276 1944-8007 |
DOI: | 10.1029/2022GL099611 |