O(S) excitation mechanism and atmospheric tides

There are two mechanisms which can account for the oxygen green line emission at 100 km Altitude, namely the Chapman and Barth mechanisms. Theoretical results and experimental data are used in order to discriminate which of these predominates in the atmosphere. In particular we have used an important new test which consists in comparing the phase of the mean diurnal variation of the green line intensity with the phase of the tide responsible for this variation. This is a powerful test because the phase of the green line variation calculated from the tidal phase has a very weak dependence on the atmospheric model used. Our conclusion is that in the atmosphere the Chapman mechanism predominates.