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Non-LTE models of Titan's upper atmosphereModels for the thermal structure of Titan's upper atmosphere, between 0.1 mbar and 0.01 nbar are presented. The calculations include non-LTE heating/cooling in the rotation-vibration bands of CH4, C2H2, and C2H6, absorption of solar IR radiation in the near-IR bands of CH4 and subsequent cascading to the nu-4 band of CH4, absorption of solar EUV and UV radiation, thermal conduction and cooling by HCN rotational lines. Unlike earlier models, the calculated exospheric temperature agrees well with observations, because of the importance of HCN cooling. The calculations predict a well-developed mesopause with a temperature of 135-140 K at an altitude of approximately 600 km and pressure of about 0.1 microbar. The mesopause is at a higher pressure than predicted by earlier calculations because non-LTE radiative transfer in the rotation-vibration bands of CH4, C2H2, and C2H6 is treated in an accurate manner. The accuracy of the LTE approximation for source functions and heating rates is discussed.
Document ID
19920033890
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Yelle, Roger V. (Arizona, University Tucson, United States)
Date Acquired
August 15, 2013
Publication Date
December 10, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 383
ISSN: 0004-637X
Subject Category
LUNAR AND PLANETARY EXPLORATION
Funding Number(s)
CONTRACT_GRANT: NAGW-2017
Distribution Limits
Public
Copyright
Other