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The thermosphere of Titan

Friedson, A. James and Yung, Yuk L. (1984) The thermosphere of Titan. Journal of Geophysical Research A, 89 (A1). pp. 85-90. ISSN 0148-0227. doi:10.1029/JA089iA01p00085.

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The diurnal variation of the vertical structure of Titan's thermosphere is calculated through simultaneous solution of the equations of heat transfer and hydrostatic equilibrium. The temperature and density profiles are found above the mesopause. The dynamical response of the thermosphere to heating is for the most part neglected. Nevertheless, we are able to draw some interesting qualitative and quantitative conclusions regarding the vertical structure. Heating of the upper thermosphere occurs primarily through absorption of solar Lyman α radiation by methane, with an additional amount of heating (≲20%) due to low-energy magnetospheric electron precipitation. The heat is conducted downward to the mesopause, where it is removed by IR cooling due principally to acetylene. The mesopause is found to occur where the density is 2.2×10^(12) cm^(−3) (736 km), and has a temperature of ∼110 K. The exospheric temperature is unlikely to exceed 225 K in the course of a Titan day. The diurnally averaged exospheric temperature is in the range 187–197 K depending on the amount of magnetospheric electron heating that is included in the model. The amplitude of the diurnal variation is found to be ≲28 K. We find that the vertical extent of the hydrogen cloud is too large to be explained in terms of simple thermal escape of hydrogen from a ∼225-K exosphere, and we conclude that other processes must be important for populating or heating the neutral torus.

Item Type:Article
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Yung, Yuk L.0000-0002-4263-2562
Additional Information:© 1984 American Geophysical Union. Received August 30, 1982; revised October 10, 1983; accepted October 11, 1983. The authors wish to thank A. P. Ingersoll, M. Allen, M. E. Summers, and G. R. Gladstone for helpful discussions. This research was supported by NASA grant NSG 7376 to the California Institute of Technology. Contribution 3907 from the Division of Geological and Planetary SciencesC, alifornia Institute of Technology. The Editor thanks R. E. Hartle and D. Strobel for their assistance in evaluating this paper.
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Caltech Division of Geological and Planetary Sciences3907
Issue or Number:A1
Record Number:CaltechAUTHORS:20140923-133141023
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Official Citation:Friedson, A. J., and Y. L. Yung (1984), The thermosphere of Titan, J. Geophys. Res., 89(A1), 85–90, doi:10.1029/JA089iA01p00085.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49947
Deposited By: Jason Perez
Deposited On:23 Sep 2014 23:01
Last Modified:10 Nov 2021 18:50

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