Magnetic mirroring in an incident proton beam

We point out that the influence of magnetic-field nonuniformity on redirect ing the pitch angle of a particle is independent of the particle's charge a nd thus is identical for protons and neutral hydrogen atoms. Under certain circumstances one can then speak of "magnetic mirroring" of hydrogen atoms as well as of protons. In the case of an energetic proton beam incident on the upper atmosphere, the study of the influence of magnetic held on both p rotons and H atoms can be relevant to inferring information about proton au rora from measurements of upgoing energetic particles observed from space. In a model that here neglects collisional angular redistribution of the par ticles, the total particle and energy albedos are approximately independent of the energy of the incident particles and of the atmospheric temperature . However, the separate proton and H atom albedos have a strong dependence on the incident energy. We also reinvestigate how to handle energy conserva tion properly in the presence of a nonuniform magnetic field, to provide a good validation for proton transport models.