ANALYTIC EXPOSPHERE MODELS FOR GEOCORONAL APPLICATIONS

A modification of the analytic approach to planetary exospheres of Chamberlain (1963, Planet. Space Sci. 11, 901) is presented, intended for use in the analysis of geocoronal observations. The extent of the satellite hydrogen atom population is delineated with a spherical exopause, and the kinetic distribution function (KDF) is parameterized in terms of an effective exobase density n(s) and temperature T(s) having values distinct from ballistic values and expected to reflect the effects of charge exchange collisions in the topside ionosphere and plasmasphere: n(s) > n(c) and T(s) < T(c). Application to averaged atomic hydrogen density distributions generated by Monte Carlo simulation (Tinsley et al., 1986, J. geophys. Res. 91, 13,631) is made to illustrate the meaning of the satellite KDF parameters. The empirical model derived from DE-1 Ly-alpha measurements by Rairden et al. (1986, J. geophys. Res. 91, 13,613) is also discussed.