Seasonal/latitudinal variations in the satellite observed aerosol properties in the stratosphere and upper troposphere during the eruption of Alaid and Pagan A heterogeneous ion-chemical model for the upper mesosphere

Abstract

A detailed heterogeneous ion model is used to computer in the charged and neutral dust concentrations in the mesosphere and lower thermosphere (80-96 km). In the model various modes of dust charging are considered including the process of multiple charging of dust. Positively charged dust particles are singly charged irrespective of their size, whereas multiple negative charges can be found on large sized (radius <i>r</i>) dust particles (<i>r</i> >> 1 nm). Below about 83 km photoionization of dust dominates over collisional positive charging of dust (attachment of positive ions to neutral dust), whereas collisional negative charging of dust (attachment of electrons and negative ions to dust) dominates over photodetechment in the entire height range of interest. The dust contours show layers structure with the lowest layer occurring at the Noctilucent Cloud height, while the uppermost peak coinciding with the altitude where metal ion layer exists. Further, the wave structure in the dust contours indicates the turbulence characteristics of the mesopause region. The results are discussed in the light of relevant theoretical and experimental information available in the literature about the mesospheric dust. The effects of possible ozone enhancement and mesospheric cooling on the model computed dust densities are also discussed. The results emphasize the importance of including the mesospheric dust, and hence the importance of heterogeneous ion chemistry, in the model studies of the mesosphere.