Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov-Gerasimenko
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BORIS DOI
Date of Publication
2016
Publication Type
Article
Division/Institute
Author
Cessateur, G. | |
Keyser, J. De | |
Maggiolo, R. | |
Gibbons, A. | |
Gronoff, G. | |
Gunell, H. | |
Dhooghe, F. | |
Loreau, J. | |
Vaeck, N. | |
Briois, C. | |
Combi, M. R. | |
Fiethe, B. | |
Fuselier, S. A. | |
Gombosi, T. I. | |
Neefs, E. |
Series
Journal of Geophysical Research: Space Physics
ISSN or ISBN (if monograph)
2169-9380
Publisher
AGU Publications
Language
English
Publisher DOI
Description
Observations of the green and red-doublet emission lines have previously been realized for several comets. We present here a chemistry-emission coupled model to study the production and loss mechanisms of the O(¹S) and O(¹D) states, which are responsible for the emission lines of interest for comet 67P/Churyumov-Gerasimenko. The recent discovery of O₂ in significant abundance relative to water 3.80 ± 0.85% within the coma of 67P has been taken into consideration for the first time in such models. We evaluate the effect of the presence of O₂ on the green to red-doublet emission intensity ratio, which is traditionally used to assess the CO₂ abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O₂ into account leads to an underestimation of the CO₂ abundance within 67P, with a relative error of about 25%. This strongly suggests that the green to red-doublet emission intensity ratio alone is not a proper tool for determining the CO₂ abundance, as previously suggested. Indeed, there is no compelling reason why O₂ would not be a common cometary volatile, making revision of earlier assessments regarding the CO₂ abundance in cometary atmospheres necessary. The large uncertainties of the CO₂ photodissociation cross section imply that more studies are required in order to better constrain the O(¹S) and O(¹D) production through this mechanism. Space weather phenomena, such as powerful solar flares, could be used as tools for doing so, providing additional information on a good estimation of the O₂ abundance within cometary atmospheres.
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File | File Type | Format | Size | License | Publisher/Copright statement | Content | |
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jgra52340 (1).pdf | text | Adobe PDF | 726.62 KB | Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) | published |