The Ionized Atmosphere Ion Composition and Number Density

The presence of ionization in the upper atmosphere was first demonstrated about half a century ago by reflecting radio waves from the ambient plasma1J, and by this technique it was shown that the ionosphere was clearly structured, several ledges  

So the chemistry of the F-region is generally well-understood and detailed chemical models have been constructed which can predict reasonably well the observed electron density and ionic composition28,29 These models are based on laboratory data for ion-neutral reactions such as (4), and dissociative recombination reactions (Sect. 3.2.4), such as 

The origin and behaviour of these cluster ions has been the basis of much of the work on atmospheric ion chemistry during the last decade. The problem which is still not resolved in detail, is to explain how the primary ions NO+ and 02+are converted to the observed water clusters, i. e. 

Such reactions, together with binary switching reactions of the kind 

As is suggested by reaction (9), the ambient negative ions also are complex clusters. In-situ measurements of the negative ion composition have been made by Narcisi et al.47) and Krankowsky et al.S8 and whilst there is no doubt that water clusters dominate, there remains some doubt as to the nature of the core ions, i. e. whether the ions are predominantly COj (H20)m or N03 (H20)m. More of these very difficult sampling experiments are necessary to clarify the situation. 

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