Changes in the Physical Environment of the Inner Coma of 67P/Churyumov–Gerasimenko with Decreasing Heliocentric Distance

Dennis Bodewits 1 Luisa M. Lara 2 Michael F. A'Hearn 3, 1 Florangela La Forgia 4 Adeline Gicquel 5 Gabor Kovacs 5 Jörg Knollenberg 6 Monica Lazzarin 4 Zhong-Yi Lin 7 Xian Shi 5 Colin Snodgrass 8 Cécilia Tubiana 5 Holger Sierks 5 Cesare Barbieri 4 Laurent Lamy 9 Rafael Rodrigo 10, 11 Detlef Koschny 12 Hans Rickman 13 Horst Uwe Keller 14 Maria Antonietta Barucci 15 Jean-Loup Bertaux 16 Ivano Bertini 17 Steve Boudreault 5 Gabriele Cremonese 18 Vania Da Deppo 19 Björn Davidsson 13 Stefano Debei 20 Mariolino de Cecco 21 Sonia Fornasier 15 Marco Fulle 22 Olivier Groussin 9 Pedro J. Gutiérrez 2 Carsten Güttler 5 Stubbe F. Hviid 6 Wing-Huen Ip 7 Laurent Jorda 9 J.-Rainer Kramm 5 Ekkehard Kührt 6 Michael Küppers 23 José-Juan López-Moreno 2 Francesco Marzari 4 Giampiero Naletto 17, 24, 19 Nilda Oklay 5 Nicholas Thomas 25 Imre Toth 26 Jean-Baptiste Vincent 5
Abstract : The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, O i, CN, NH, and NH2 filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO2 rather than H2O is a significant source of the [O i] 630 nm emission. A strong plume-like feature observed in the CN and O i filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO2/H2O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus.
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Submitted on : Thursday, October 27, 2016 - 1:46:38 PM
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Dennis Bodewits, Luisa M. Lara, Michael F. A'Hearn, Florangela La Forgia, Adeline Gicquel, et al.. Changes in the Physical Environment of the Inner Coma of 67P/Churyumov–Gerasimenko with Decreasing Heliocentric Distance. Astronomical Journal, American Astronomical Society, 2016, 152 (5), pp.130. ⟨10.3847/0004-6256/152/5/130⟩. ⟨insu-01388677⟩



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