PROTON TRANSPORT MODEL IN THE IONOSPHERE - 2 - INFLUENCE OF MAGNETIC MIRRORING AND COLLISIONS ON THE ANGULAR REDISTRIBUTION IN A PROTON-BEAM

We investigate the influence of magnetic mirroring and elastic and ine lastic scattering on the angular redistribution in a proton/hydrogen b eam by using a transport code in comparison with observations. H-emiss ion Doppler profiles viewed in the magnetic zenith exhibit a red-shift ed component which is indicative of upward fluxes. In order to determi ne the origin of this red shift, we evaluate the influence of two angu lar redistribution sources which are included in our proton/hydrogen t ransport model. Even though it generates an upward flux, the redistrib ution due to magnetic mirroring effect is not sufficient to explain th e red shift. On the other hand, the collisional angular scattering ind uces a much more significant red shift in the lower atmosphere. The re d shift due to collisions is produced by <1-keV protons and is so smal l as to require an instrumental bandwidth <0.2nm. This explains the ab sence of measured upward proton/hydrogen fluxes in the Proton I rocket data because no useable data concerning protons <1 keV are available. At the same time, our model agrees with measured ground-based II-emis sion Doppler profiles and suggests that previously reported red shift observations were due mostly to instrumental bandwidth broadening of t he profile. Our results suggest that Doppler profile measurements with higher spectral resolution may enable us to quantify better the angul ar scattering in proton aurora.