The OI λ1304 and λ1356 emissions in aurorae

An altitude profile of the λ3914 emission of Na₂⁺ measured in an aurora by two rocket-borne spectrometers has been used to compute height-intensity profiles of the OI radiations at λ1304 and λ1356. Comparison of predictions with observations shows that the shape of the altitude profiles can better be reproduced by assuming a Doppler frequency profile rather than a Voigt profile in the radiative transfer computations. There are serious discrepancies between the observed and predicted intensity maxima for both oxygen features that could be due to the particular value for the cross sections we have adopted for excitation of oxygen by electron impact.We have also carried out calculations for two model aurorae characterized by widely differing primary electron spectra, and find that simultaneous zenith-nadir measurements would not only be useful for specifying the nature of the precipitating electron flux, but also for further testing important assumptions made in the radiative transfer calculations.