Interferometric measurements of zonal winds on Titan
Résumé
We report millimetre observations of Titan performed with the IRAM Plateau de Bure Interferometer at the rotational frequencies of HC3N(25-24) and CH3CN(12-11). The most extended configuration of the array yielded disk-resolved emission spectra of Titan with an angular resolution of 0.6''. Data were acquired in February-March 2003 and February 2004 near the greatest eastern and western elongations of Titan at high spectral resolution (lambda/Deltalambda = 5.5 × 106). Doppler lineshift measurements enable us to establish that the zonal wind flow is prograde in the upper atmosphere. Two different altitude regions are probed. Beam-integrated equatorial wind velocities of 160 (± 60) m/s and 60 (± 20) m/s are determined at respective altitudes of 300 (± 150) km (upper stratosphere) and 450 (± 100) km (lower mesosphere). The latter is the first direct determination of mesospheric wind speed on Titan.
Domaines
Astrophysique [astro-ph]
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