THE DISTRIBUTION OF HOT HYDROGEN-ATOMS PRODUCED BY ELECTRON AND PROTON PRECIPITATION IN THE JOVIAN AURORA

The energy distribution functions of nonthermal thermospheric hydrogen atoms are calculated for electron and proton precipitation in the Jov ian aurora. A numerical model taking into account the production, elas tic and inelastic relaxation and transport processes for hot H atoms i s developed. This model is based on a Monte Carlo solution of the nonl inear Boltzmann equation for hot H atoms produced by electron and prot on impact on H and H-2 and exothermic chemical reactions. The distribu tion functions show a much higher energy tail for proton than electron precipitation. It is shown that the steady state flux of hot atoms (E greater than or equal to 2 eV) is essentially isotropic. The peak and column hot H densities are about 3 x 10(5) cm(-3) and 1 x 10(14) cm(- 3) for a 100 erg cm(-2) s(-1) precipitation combining hard (22 keV) an d soft, (0.2 keV) electrons mixed with a 10 erg cm(-2) s(-1) flux of s oft (0.3 keV) protons. These column densities, coupled with the wide r ange of hot H atom energies, may play an important role in the formati on of the Lyman alpha line profile. Multiple scattering in the wings o f the Ly alpha line by the fast H atoms is shown to partly account for the broad Ly alpha profile observed in the Jovian aurora with the Hub ble space telescope.