Direct Numerical Simulation of Pluto's Extended Atmosphere
Abstract
The structure and escape of Pluto's upper atmosphere is modeled using
the Direct Simulation Monte Carlo (DSMC) method. Several atmospheric
compositions are studied consisting primarily of N2 with differing
mixing fractions of CH4 and CO. Radial profiles of temperature,
density and species distributions are calculated in a spherically
symmetric domain with a varying gravitational body force. Lower
boundary conditions are obtained from a hydrostatic, radiative model
of Pluto's lower atmosphere (Strobel, et al. 1996) and results
for pure methane are compared against Trafton's hydrodynamic, extended
atmosphere model (Trafton, et al. 1987, 1989 and Clarke, et
al. 1992). Using the DSMC approach the atmosphere is modeled
statistically by extrapolating from the motions and collisions of a
relatively small number of representative molecules. This method can
solve fully viscous, compressible, unsteady flow problems and allows
for rarefied and non-LTE effects and the diffusive separation of
multi-species gases.
Last revised: July 22, 1996