Ion-induced nucleation of atmospheric water vapor at the mesopause

Abstract

The possibility of aerosol formation at the mesopause by ion-induced water vapor nucleation is investigated. A simple kinetic model considering new information on ion-growth and -recombination processes as well as on mesospheric water vapor and temperatures is put forward. It predicts ion-nucleation to be possible only at high latitudes during local summer in a narrow height region, extending from about 88 to 91 km. Derived nucleation rates increase steeply with decreasing temperatures and electron number densities. If for the latter typical values are considered nucleation rates may become sufficiently high to account for the observed mesospheric aerosol layer. Various observed characteristic temporal and spatial variations of the aerosol layer including its response to geomagnetic activity may be explained by the model.