A new model for the interaction of auroral electrons with the atmosphere: Spectral degradation, backscatter, optical emission, and ionization

A new computational model has been created to describe the interaction of auroral electrons with the atmosphere. For electrons of energy greater than 500 eV, continuous energy losses and small angle deflections are combined in a Fokker-Planck diffusion equation that computes energy spectrums over all pitch angles throughout the atmosphere. These fluxes are then used to determine the rates of secondary electron and degraded (E < 500 eV) primary electron production at all heights. This information is used to compute upward and downward hemispherical fluxes in the energy range 0–500 eV, taking into account discrete energy losses, large angle scattering, and particle transport along magnetic field lines. The model has been used to compute energy spectrums, ionization rates, backscatter ratios, and optical emissions associated with different incident electron spectrums. For monoenergetic electrons of energy 2 keV and above the results obtained agree well with the work of Rees (1969) and Rees and Maeda (1973). At lower energies the effects of transport and elastic collisions become progressively more important, and the present results differ significantly both from the Rees and Maeda results and from those obtained from the ideas of energy degradation. Finally, spectrums typical of the nighttime auroral oval and daytime polar cusp are used to obtain the altitude dependent fluxes, ionization rates, and optical emissions.