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 Jovian aurora. A numerical model taking into account the production, elastic and inelastic relaxation and transport processes for hot H atoms is developed. This model is based on a Monte Carlo solution of the nonlinear Boltzmann equation for hot H atoms produced by electron and proton impact on H and H-2 and exothermic chemical reactions. The distribution 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) and soft, (0.2 keV) electrons mixed with a 10 erg cm(-2) s(-1) flux of soft (0.3 keV) protons. These column densities, coupled with the wide range of hot H atom energies, may play an important role in the formation of the Lyman alpha line profile. Multiple scattering in the wings of 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 Hubble space telescope.