title: Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov-Gerasimenko.
abstract: 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 O2in 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 O2on the green to red-doublet emission intensity ratio, which is traditionally used to assess the CO2abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O2into account leads to an underestimation of the CO2abundance 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 CO2abundance, as previously suggested. Indeed, there is no compelling reason why O2would not be a common cometary volatile, making revision of earlier assessments regarding the CO2abundance in cometary atmospheres necessary. The large uncertainties of the CO2photodissociation 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 O2abundance within cometary atmospheres.
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Cessateur
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium; Center for Plasma Astrophysics Katholieke Universiteit Leuven Heverlee Belgium.
authors.forename: J De
authors.initials: J
authors.lastname: Keyser
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Maggiolo
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium; Service de Chimie Quantique et Photophysique Université Libre de Bruxelles Brussels Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Gibbons
authors.affiliation: Science Directorate, Chemistry and Dynamics Branch NASA Langley Research Center Hampton Virginia USA; SSAI Hampton Virginia USA.
authors.forename: G
authors.initials: G
authors.lastname: Gronoff
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Gunell
authors.affiliation: Space Physics Division Royal Belgian Institute for Space Aeronomy Brussels Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Dhooghe
authors.affiliation: Service de Chimie Quantique et Photophysique Université Libre de Bruxelles Brussels Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Loreau
authors.affiliation: Service de Chimie Quantique et Photophysique Université Libre de Bruxelles Brussels Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Vaeck
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland; Center for Space and Habitability University of Bern Bern Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Altwegg
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland; Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor Michigan USA.
authors.forename: A
authors.initials: A
authors.lastname: Bieler
authors.affiliation: Laboratoire de Physique et Chimie de l'Environnement et de l'Espace UMR 7328 CNRS, Université dOrléans Orléans France.
authors.forename: C
authors.initials: C
authors.lastname: Briois
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland.
authors.forename: U
authors.initials: U
authors.lastname: Calmonte
authors.affiliation: Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor Michigan USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Combi
authors.affiliation: Institute of Computer and Network Engineering (IDA) TU Braunschweig Braunschweig Germany.
authors.forename: B
authors.initials: B
authors.lastname: Fiethe
authors.affiliation: Space Science Division Southwest Research Institute San Antonio Texas USA; Department of Physics and Astronomy University of Texas at San Antonio San Antonio Texas USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Fuselier
authors.affiliation: Department of Climate and Space Sciences and Engineering University of Michigan Ann Arbor Michigan USA.
authors.forename: T I
authors.initials: TI
authors.lastname: Gombosi
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland; Space Science Division Southwest Research Institute San Antonio Texas USA.
authors.forename: M
authors.initials: M
authors.lastname: Hässig
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Le Roy
authors.affiliation: Engineering Division Royal Belgian Institute for Space Aeronomy Brussels Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Neefs
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Rubin
authors.affiliation: Physikalisches Institut University of Bern Bern Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Sémon
keywords: 67P/Churyumov‐Gerasimenko; ROSINA/DFMS; airglow; oxygen line emissions