Excitation of helium in the aurora

Abstract

The populations of the excited levels of a helium atom traversing the atmosphere with an original energy of 256 keV are calculated using the method of statistical equilibrium. Because of the present inadequate knowledge of helium cross-sections, the calculations are only an exploratory approach toward the problem of helium in aurorae. It is estimated that each 256 keV helium particle produces 450 photons of λ10830 and 40 photons of λ5876 during its passage through the atmosphere. The profile and luminosity curve of λ5876 and λ10830 are predicted. Observational data of helium emissions are discussed.