Computer Science – Sound
Scientific paper
Sep 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996dps....28.0601e&link_type=abstract
American Astronomical Society, DPS meeting #28, #06.01; Bulletin of the American Astronomical Society, Vol. 28, p.1079
Computer Science
Sound
Scientific paper
The asymmetry of the central flash observed at the IRTF for a stellar occultation by Triton on 1995 Aug. 14 (Olkin et al., to be submitted to Icarus) can be readily explained if Triton's atmosphere within the radius range probed by the occultation (1380-1460 km) is distorted from spherical symmetry. The offset of the peak of the central flash from the midtime between immersion and emersion, as well as the different slopes of the rising and falling parts of the central flash, imply that surfaces of constant refractivity within Triton's atmosphere (for sub-Earth latitude B = -48.7 deg ) are not circular. Modeling the central flash requires that this surface has a greater radius of curvature than average on the southern limb, or a smaller radius of curvature on the northern limb. The magnitude of the ``flattening'' is ~ 0.02, with a symmetry axis consistent with Triton's rotation axis. Since this large flattening would be totally unexpected from Triton's slow rotation (5.87684 day period), we must seek other explanations. These include ~ 100 m s(-1) , cyclostrophic zonal winds (sound speed = 140 m s(-1) ; Stansberry et al., this conference), substantial gravitational anomalies (J_2 ~ 0.01), compositional gradients, or large changes in the scale height around the visible limb (although these appear less likely from the results of Olkin et al.). Limits on gravity anomalies and the flattening of the surface figure could be placed from Voyager data, but these have apparently not been published (Davies et al. 1991, JGR 96, 15,675). The fitted light-curve models to the central flash also support the conclusion of Olkin et al. that--contrary to present models (Krasnopolsky et al. 1993, JGR 98, 3065; Yelle et al. 1991, Icarus 89, 347; Strobel et al. 1996, Icarus 120, 266)--Triton's atmosphere is nearly isothermal or adiabatic in the region probed by the stellar occultation (the 1.5 mu bar region). More can be learned about Triton's figure from multiple central-flash chords in future occultations. This research was supported in part by NASA Grants NAGW-1494 (MIT), NAG2-836 (Lowell), and contributions from the Friends of Lowell Observatory.
Elliot James L.
Olkin Catherine B.
Stansberry John Arthur
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