Radial dependence of the density in a planetary exosphere
Abstract
The departure of a onecomponent planetary atmosphere from hydrostatic equilibrium is studied with a new moment method of solution of the nonlinear Boltzmann equation. The velocity distribution function of atmospheric particles is expanded in a set of halfrange basis functions, that is, a set of basis functions for the velocity distribution function corresponding to upward and downward moving particles, respectively. A set of balance equations is derived from the Boltzmann equation by evaluating the equations of change of the lower order moments of the distribution function, namely the density and particle flux. An asymptotic analysis of the moment equations for the density and particle flux yields a density profile that decays as r^{3} and demonstrates that the total mass of the atmosphere is finite in contrast to the usual barometric density.
 Publication:

Planetary and Space Science
 Pub Date:
 February 1987
 DOI:
 10.1016/00320633(87)900894
 Bibcode:
 1987P&SS...35..199W
 Keywords:

 Atmospheric Density;
 Exosphere;
 Planetary Atmospheres;
 Density Distribution;
 Distribution Functions;
 Particle Motion;
 Velocity Distribution;
 Lunar and Planetary Exploration