Chemistry of middle atmospheric ionization-a review

Abstract

We describe in this article the observations and chemistry of the ionization of the Earth's middle atmosphere, here defined as the region between 100 km and the tropopause, consisting of the D-region (50–100 km) and the stratosphere. Observational data on electron and ion distributions and on ion composition, both for the D-region and the stratosphere (for the latter more limited), are discussed. The exciting new possibilities of extending incoherent scatter facility to D-region heights is examined. Chemical schemes, which were until recently confined to conditions in the D-region, have now been extended to stratospheric heights and new experimental data have helped in identifying clustering paths. Some of these schemes are also outlined. An important consideration is the role played by aerosols and the possibility of determining Aitken particle concentrations from localized depletions in ion considerations.