Research project MO/35/001 (Research action MO)
The aim of this project is to study the velocity distribution function of the particles escaping from the ionosphere of a planet. We wil be interested by the transition region between the collision-dominated regime at low altitude and the collisionless regime at high altitudes. The problem of the transition region is still unsolved in dynamic plasma theory. A spectral method already developed to solve the Fokker-Planck equation will be used to describe the diffusion and upward bulk motion of minor ions through a background plasma. The ion distribution function will be determined as a function of the altitude and of the components of the particle velocity vector for realistic boundary conditions. The results of this kinetic model wil then be compared with those of earlier models describing the limit cases of collisionless plasma and collision dominated plasma. The resolution of this problem is sufficiently general to be adapted to other problem of gas escaping such as solar wind.
