A Model Study of the Vertical Distributions and Escape Fluxes of the Major and Minor Species in Titan’s Thermosphere Under Different Conditions
Jen-Kai Hsu1*, Wing-Huen Ip1,2, Mao-Chang Liang3, Jun Cui4, R. S. Perryman5, J. H. Waite5
1Graduate Institute of Space Science, National Central University, Taoyuan, Taiwan
2Graduate Institute of Astronomy, National Central University, Taoyuan, Taiwan
3Research Center for Environmental Change, Academia Sinica, Taipei, Taiwan
4National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
5Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
* presenting author:Jen Kai Hsu, email:tabriskai.hsu@gmail.com
From the measurements of the Ion Neutral Mass Spectrometer (INMS) on the Cassini spacecraft at different close encounters with Titan, it is know that the vertical temperature profile and density distributions of N2, CH4, H2 and other species could have large variations which might be driven by environmental effects such as solar radiation and magnetospheric interaction. For example, the atmospheric temperature as determined from the N2 density profiles can vary between 120 K and 175 K. Following the treatment of Li et al. (PSS, 104 (2014) 48-58) by applying a non-monotonic eddy diffusivity profile, we compute the vertical distributions of different species between Titan’s surface to 2000 km altitude, for a range of atmospheric temperatures. Intercomparison between the model results and observations leads to better understanding of the production mechanisms of the minor species like C2H2, C2H4, C2H6 and others, all important to the hydrocarbon budgets of Titan’s atmosphere and surface, respectively. Furthermore, such detailed photochemical calculations will also yield accurate estimates of the escape fluxes of H, H2 and CH4 into the circum-planetary region.

Keywords: Ion Neutral Mass Spectrometer (INMS), Cassini spacecraft