中层大气钠层的流星蒸发模式

本文计算了地球中层大气的钠层模式。在此模式中,流星蒸发是形成钠层的源而尘埃的吸附足汇。本文考虑和比较了有关钠层形成机制的已往工作中所出现过的所有光化学反应,选出了四十个合理而重要的化学反应作为本模式的化学基础。模式也考虑进了高度变化的涡流扩散和带电粒子受地磁场作用的向下飘移等机制。本文对各化学反应和模式中各个因素的重要性作了比较和评价。本文计算结果表明,在各高度上中层大气中的钠及其化合物的相对浓度主要取决于化学反应过程本身,与源、汇及各层间扩散机制等关系不大。虽然在钠层模式计算中必须考虑到十种钠成分,但105公里以上主要成分足钠离子(Na+)。80公里以下主要成分是氢氧化钠(NaOH)。80公里到105公里间主要成分是中性钠原子(Na)。所有成分的总浓度主要地取决于源和汇随高度的分布。大气背景及电离常数的变化可以引起钠层相当显著的季变化和周日变化。理论计算结果与历年来的观测结果作比较后可以看到两者大体上符合得相当好。 

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.