The profile of the hydrogen H-beta emission line in proton aurora

Models of hydrogen-proton transport in proton aurora predict the line profi le of the hydrogen emissions from specified incident proton precipitation. We are using a model that includes collisional angular redistribution which leads to upward moving proton and hydrogen fluxes. For ground-based observ ation in the magnetic zenith this causes a small Doppler broadening toward the red in the line profile. The precipitating energetic hydrogen atoms are responsible for the prominent Doppler shift toward the blue. The resulting line profile has thus both a widened red and a widened blue wing. Using a spectrometer with sufficient spectral resolution to distinguish the red-shi fted wing of the line from the instrumental line broadening, we obtain Hg l ine pro files (486.1 nm). Comparing the predicted line shapes to our observ ations, we find the red-shifted wing is due to upward moving hydrogen as pr edicted by the angular redistribution in the model calculations. The shape of the blue-shifted wing, rather than the location of the peak of the blue- shifted line profile, is a suitable indicator of the mean energy of the pr ecipitating proton flux.