Observation of a tilt of Titan's middle-atmospheric superrotation

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.05.014 Byline: Richard K. Achterberg (a), Barney J. Conrath (b), Peter J. Gierasch (b), F. Michael Flasar (c), Conor A. Nixon (a) Keywords: Titan; Atmospheres; structure; Atmospheres; dynamics; Infrared observations Abstract: Maps of isotherms on surfaces of constant pressure in Titan's middle atmosphere encircle the poles but show an offset, implying that the mean zonal flow has an axis of symmetry that is tilted relative to the spin axis of the solid body. The effect is seen in both hemispheres around a consistent axis. Periodogram analysis of the temperature field shows that wavenumber one, the signal corresponding to the spin tilt, is the strongest wave component. We conjecture that the tilt of the atmospheric spin is due to a feedback between the flow and the solar heating. The spin adjusts itself to align the spin equator with the direction toward the Sun, and thereby maximizes the efficiency with which the meridional circulation pumps angular momentum upward to generate superrotation. Author Affiliation: (a) University of Maryland, Department of Astronomy, College Park, MD 20742, USA (b) Department of Astronomy, Cornell University, Ithaca, NY 14853, USA (c) NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Article History: Received 11 December 2007; Revised 11 April 2008