Pitch angle distributions of auroral protons

The correspondence between the variable energy spectra and pitch-angle distributions of protons with energies between 0.4 and 30 keV, measured from the AUREOLE I satellite in the auroral zone about 400km altitude and more or less stable spectra profiles of the auroral hydrogen emission observed from the ground is discussed. Pitch angle distributions were generally found to be from isotropic to quasi trapped (upper hemisphere) in a proton oval zone pratically coincident with the proton oval deduced by Montbriand, and Fukunishi and Tohmatsu. In several cases the pitch-angle distributions are field-aligned. The comparison with theoretical proton distributions, calculated using the Monte Carlo method, shows that these distributions can lead to the hydrogen emission profile forms observed for typical precipitating protons in the range 5-30 keV. The importance of the effect of space diffusion on precipitating protons in the auroral atmosphere, as evidenced by the Monte Carlo calculations is stressed for evaluation of the effects of auroral emission and ionization in the proton aurora