Physics
Scientific paper
Aug 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009icar..202..632s&link_type=abstract
Icarus, Volume 202, Issue 2, p. 632-641.
Physics
16
Scientific paper
In Strobel [Strobel, D.F., 2008. Icarus, 193, 588-594] a mass loss rate from Titan's upper atmosphere, ˜4.5×1028 amus-1, was calculated for a single constituent, N2 atmosphere by hydrodynamic escape as a high density, slow outward expansion driven principally by solar UV heating due to CH4 absorption. It was estimated, but not proven, that the hydrodynamic mass loss is essentially CH4 and H2 escape. Here the individual conservation of momentum equations for the three major components of the upper atmosphere (N2, CH4, H2) are solved in the low Mach number limit and compared with Cassini Ion Neutral Mass Spectrometer (INMS) measurements to demonstrate that light gases (CH4, H2) preferentially escape over the heavy gas (N2). The lightest gas (H2) escapes with a flux 99% of its limiting flux, whereas CH4 is restricted to ⩾75% of its limiting flux because there is insufficient solar power to support escape at the limiting rate. The respective calculated H2 and CH4 escape rates are 9.2×1027 and 1.7×1027 s-1, for a total of ˜4.6×1028 amus-1. From the calculated densities, mean free paths of N2, CH4, H2, and macroscopic length scales, an extended region above the classic exobase is inferred where frequent collisions are still occurring and thermal heat conduction can deliver power to lift the escaping gas out of the gravitational potential well. In this region rapid acceleration of CH4 outflow occurs. With the thermal structure of Titan's thermosphere inferred from INMS data by Müller-Wodarg et al. [Müller-Wodarg, I.C.F., Yelle, R.V., Cui, J., Waite Jr., J.H., 2008. J. Geophys. Res. 113, doi:10.1029/2007JE003033. E10005], in combination with calculated temperature profiles that include sputter induced plasma heating at the exobase, it is concluded that on average that the integrated, globally average, orbit-averaged, plasma heating rate during the Cassini epoch does not exceed ˜5×108 eVcm-2s-1 (˜0.0008 ergcm-2s-1).
No associations
LandOfFree
Titan's hydrodynamically escaping atmosphere: Escape rates and the structure of the exobase region does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Titan's hydrodynamically escaping atmosphere: Escape rates and the structure of the exobase region, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Titan's hydrodynamically escaping atmosphere: Escape rates and the structure of the exobase region will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-833763