Formation and growth of photochemical aerosols in Titan's atmosphere

摘要: Recent developments in our understanding of the morphology (shape and size) haze aerosols Titan's atmosphere, aggregate particles their associated optical properties (West 1990, West Smith 1991), have been considered light a microphysical modeling aerosols. Using an Eulerian model rather similar to one Toon et al. (1980), it is shown that growth may be divided two stages. The first corresponds initial near formation altitude by accretion very small elementary (synthetized oligomers). Due large number accreted particles, this stage leads nearly spherical (called “monomers” Smith). In second stage, these (“monomers”) settle atmosphere stick together forming aggregates, same kind as those obtained experimentally Bar-Nun (1988). classical assumption which made all existing models, valid during stage. mean ratio between masses colliding quantified function using specific index (mass sharing index, MSI). From criterion, previously defined regions (the region inside monomers are generated, settling where aggregates build up) clearly separated boundary them precisely located. Identifying monomer radius with mass-averaged at boundary, extremely sensitive created. reason residence time altitude, determines extent size monomers, increasing pressure. strong dependence on pressure (thus altitude) calculated different sets parameters (eddy diffusion coefficient, electrical charge, mass production rate, …) order cover widest range possibilities. favored his analysis polarizing haze, found lie from 350 400 km.