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Astron. Astrophys. 333, L43-L46 (1998)

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Letter to the Editor

ISO observations of Uranus: The stratospheric distribution of C2 H2 and the eddy diffusion coefficient

Th. Encrenaz 1, H. , Feuchtgruber 2, S.K. , Atreya 3, B. , Bézard 1, E. , Lellouch 1, J. , Bishop 4, S. , Edgington 3, Th. , de , Graauw 5, M. , Griffin 6, M.F. and Kessler 7

1 DESPA, Observatoire de Paris, F-92195 Meudon, France
2 Max-Planck-Institut für Extraterrestrische Physik, D-85748 Garching, Germany
3 The University of Michigan, Ann Arbor, MI 48109-2143, USA
4 Computational Physics Inc., Virginia, USA
5 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
6 Queen Mary and Westfield College, Miles End Road, London E1 4NS, UK
7 ISO Science Operation Center, ESA, P.O. Box 50727, E-28080 Madrid, Spain

Received 16 February 1998 / Accepted 6 March 1998

Abstract

The infrared spectrum of Uranus has been recorded between 7 and 16.5 µm with the grating mode of the Short-Wavelength Spectrometer of ISO, with a resolving power of 1500. The 6-12 µm spectrum of Uranus has also been recorded at lower resolution (R=90) by the PHOT instrument in spectroscopic mode. The spectra show no signatures other than the C2 H2 band centered at 13.7 µm. From the absence of emission in the region of the CH4 7.7 µm band, and by fitting the C2 H2 data on the basis of a photochemical model, the eddy diffusion coefficient is retrieved (in the range 5 103 -104 cm2 s-1 at the homopause). This result is consistent with the values previously derived from the Voyager UV occultation experiments.

Key words: planets and satellites – Uranus – infrared: solar system

Send offprint requests to: Th. Encrenaz

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© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998
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