THE ABLATION MODEL OF THE SOIDUM LAYER IN THE MIDDLE ATMOSPHERE

Ameteor ablation model of the sodium layer is developed,in which ablation is the source and depositon on dust particles is the sink.All the photochemical reactions which appeared in previous work are considered and 40 reactions are picked out,ot be included in the model.Kealistic eddy diffusion and downward electrodynamic transport are also incorporated in the model.The importance of the photochemical reactions and the various other aspects of the model are evaluated and compared with each other.Results show that the relative concentrations of various species of sodium and its compounds are mainly determined by a set of photochemical reactions.The main species above 105 km is Na⁺,below 80 km is NaOHand between 80 km and 105 km is Na.The total concentration is mainly determined by the profiles of ablation and dust concentration.The atmospheric background and the photo-ionization rate constants can produce seasonal and diurnal variations of the sodium layer.Comparison of the theoretical model with observation shows generally a good agreement.