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Nonthermal O(1S) and O(1D) populations in cometary atmospheres
Hubert, Benoît; Bisikalo, D.V.; Shematovich, V.I. et al.
2013AGU Fall Meeting
Editorial reviewed
 

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Abstract :
[en] Recent developments in the field of cometary science have motivated many studies dealing with the nucleus composition and mineralogy, and also with the photochemistry of the coma. In particular, ground based observations have shown that the visible oxygen emissions at 557.7 and 630 nm, both belonging to the Rosetta-VIRTIS-M passband, present different line profiles, pointing to specific photochemical processes. In this work, we present a Monte Carlo simulation of the O(1D) and O(1S) photochemistry including photodissociation of H2O, CO2 and CO, quenching, collisional thermalization and radiative decay. The model solves Boltzmann's integro differential equation including sources and sinks, as well as a prescribed expansion velocity of the coma. The energy distribution functions (EDF's) of O(1S) and O(1D) are computed at cometocentric distances ranging between 10 and 5000 km. We find that the EDF's of both O(1D) and O(1S) are strongly nonthermal, up to a degree that sharply varies with cometocentric distance, as thermalization is less efficient when the density of the dominant species is reduced. It follows that the Doppler profile of the visible radiations emitted by both species is non-gaussian in a frame of reference moving with the expanding coma. The nonthermal volume emission rate is then integrated along a set of chosen line of sights, accounting for the explicit Doppler profiles derived from the EDF's as well as the expansion motion, and the Doppler profile of the full coma is computed. It appears that most of the line width is due to the expansion motion, although the detailed line shape remains sensitive to the nonthermal nature of the EDF's. Our computation can then be compared with the line profiles observed from the ground with the UVES spectrograph mounted on the ESO-VLT.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Hubert, Benoît  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Bisikalo, D.V.
Shematovich, V.I.
Gérard, Jean-Claude  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Decock, Alice ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Manfroid, Jean  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Hutsemekers, Damien ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS)
Jehin, Emmanuel  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Language :
English
Title :
Nonthermal O(1S) and O(1D) populations in cometary atmospheres
Publication date :
December 2013
Event name :
AGU Fall Meeting
Event date :
Decembre 2013
Audience :
International
Peer reviewed :
Editorial reviewed
References of the abstract :
2013AGUFM.P23H..05H
Available on ORBi :
since 03 April 2015

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