37th DPS Meeting, 4-9 September 2005
Session 45 Titan's Atmosphere
Poster, Wednesday, September 7, 2005, 6:00-7:15pm, Music Recital Room

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[45.17] Modeling the photochemical production of haze particles in Titan's atmosphere.

P. Lavvas (Department of Physics, University of Crete, Greece), I.M. Vardavas (Department of Physics, University of Crete, Greece and Foundation of Research and Technology, Crete, Greece), A. Coustenis (Paris Observatory, Meudon, France), D. Hatzidimitriou, I. Papamastorakis (Department of Physics, University of Crete, Greece and Foundation of Research and Technology, Crete, Greece)

Titan's vertical atmospheric temperature profile, atmospheric chemical composition and haze structure are controlled by many processes. In this work we present a self-consistent 1D simulation of radiation transfer, photochemistry and haze microphysics that determine Titan's atmosphere and haze. The atmospheric model extends from the surface up to the lower thermosphere and incorporates: high resolution radiation transfer codes for solar and thermal radiation, complete neutral species photochemical evolution and a detailed Eulerian description of the microphysical haze particle growth.

Chemical analysis of the laboratory produced haze analogs, suggests that the most probable photochemical pathways leading to haze formation, include copolymers of acetylene, hydrogen cyanide, aromatics and others. Although these pathways produce a Haze monomers mass production rate of the correct magnitude to fit the geometric albedo, their production profiles are significantly different from the simplified ones used in previous simulations.

The photochemical part of the model produces the vertical profile of all the important hydrocarbons and nitriles in Titan's atmosphere including the polymerisation of organic species for Haze production. This interaction of the Haze precursors with the chemistry is considered to take place until the precursors reach a typical mass of ~1000 amu, after which the polymers chemical growth ceases and the conglomeration of the Haze particles commences. The resulting distribution of different size particles, along with the rest of the species interacting with the radiation field are included in the radiative/convective part of the model for the calculation of the thermal structure. The model iterates between these processes until a steady state is reached.

The results presented are validated against observed data (geometric albedo, chemical composition, thermal structure, etc.) in order to understand better the physical processes that control: Titan's methane abundance; the production, structure and radiative properties of the haze; and the radiative properties of Titan's atmosphere and surface.

The author(s) of this abstract have provided an email address for comments about the abstract: lavvas@physics.uoc.gr

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