ISO observations of Uranus: The stratospheric distribution of C_2H_2 and the eddy diffusion coefficient
Kessler, M. F.; Lellouch, E.; Feuchtgruber, H.; Atreya, S. K.; Griffin, M.; Encrenaz, Th.; Bishop, J.; Bezard, B.; Edgington, S.; Degraauw, Th.
France, Germany, United States, Netherlands, United Kingdom, Spain
Abstract
The infrared spectrum of Uranus has been recorded between 7 and 16.5mu m with the grating mode of the Short-Wavelength Spectrometer of ISO, with a resolving power of 1500. The 6-12mu m 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 C_2H_2 band centered at 13.7mu m. From the absence of emission in the region of the CH_4 7.7mu m band, and by fitting the C_2H_2 data on the basis of a photochemical model, the eddy diffusion coefficient is retrieved (in the range 5 10(3) -10(4) cm(2) s(-1) at the homopause). This result is consistent with the values previously derived from the Voyager UV occultation experiments.