36th DPS Meeting, 8-12 November 2004
Session 22 Titan II: Chemistry
Oral, Wednesday, November 10, 2004, 10:30-12:00noon, Lewis

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[22.06] The two stellar occultations of November 14, 2003: revealing Titan's stratosphere at sub-km resolution

B. Sicardy, F. Colas, T. Widemann, A. Fienga, S. Lacour, J. Lecacheux, E. Lellouch, S. Pau, S. Renner, F. Roques (Paris Obs.), I. Glass (SAAO), D. Baba, T. Nagata (Nagoya Univ.), F. Ferri (Padova Univ.), C. Martinez (LLADA Buenos Aires), W. Beisker, S. Enke, K.-L. Bath, F. Bode, H.-J. Bode, D. Fiel, M. Kretlow, M. Hernandez, D. Horns, J. Luedemann, H. Luedemann, A. Tegtmeier (IOTA-ES), C. deWitt, B. Fraser, T. Jones, P. Shonau, C. Turk (Amateurs R. South Africa), P. Meintjies (Boyden Obs.), R.R. Howell (WIRO), M. Kidger (IAC Tenerife), J.L. Ortiz (IAA Granada), P. Rosenzweig, O. Naranjo (Merida Univ. Venezuela), M. Rapaport (Bordeaux Obs.)

On November 14, 2003, Titan occulted two bright Tycho stars (V= 8.4 and V= 10.3). The first event was observed in the Indian Ocean and southern Africa, while the second one was followed from western Europe, northern and central Americas. Data were gathered by both professional and amateur astronomers, using fixed and portable telescopes at wavelengths ranging from visible to near IR (K band).

Inversion of the light curves provide sub-km resolution density and temperature profiles of Titan's upper stratosphere (altitude range ~ 250-550 km, pressure ~ 1-250 \mubar). A well confined inversion layer, with a temperature increase of more than 15 K in about 6 km, is ubiquitous in the data near 510 km altitude (1 \mubar). This global feature is either due to a localized heating source or to dynamical processes yet to be determined.

A central flash is visible in five of the light curves taken from the first event. We model the flash shape and intensity, using ray tracing with a prescribed limb shape (linked to a given zonal wind regime) and opacity. Observations are consistent with a strong jet at northern latitudes (~ 200 m s-1 at latitude 55N), decreasing to ~ 140m s-1 at equator, and tapering off to zero in the sourthern hemisphere. We do not detect the northern polar hood predicted by some GCM models, up to latitude 67N. Thus, the polar hood is either non-existent, or is present at latitudes north of 67N.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.