The ionization by solar UV-radiation and energetic particle precipitation causes variation in upper atmosphere constituent concentrations. Ionization and chemical reactions lead to a production of odd nitrogen in the mesosphere, which is important to the ozone balance of the atmosphere. Under polar night conditions the nitric oxides are long lived and can be carried down into the lower atmosphere, where they destruct stratospheric ozone.

The GOMOS and the MIPAS instruments together with the EISCAT incoherent scatter radars and a network of other ground measurements will provide a so far unique possibility to address this scientific problem in the auroral region. The Sodankylä Geophysical Observatory (SGO) and the Finnish Meteorological Institute (FMI) are developing a detailed chemical model on the base of the Sodankylä Ion Chemistry Model (SIC) in order to utilize these new data sets and study the effects of solar radiation and energetic particles on mesospheric and stratospheric concentrations. The purpose is to model in detail the process chain starting from ionization in the mesosphere to the destruction of ozone in the stratosphere.