Exoplanetary atmosphere models and chemistry
Résumé
Exoplanet atmospheres that can be characterized with current instrumentations are hot, subjected to very high UV fluxes and undergo strong circulation, a situation radically different from what is found in the atmospheres of our own Solar System. As a matter of fact, traditional models, adapted to model (sub)stellar atmospheres or Solar System planetary atmospheres, fail to provide a reliable description of their composition. It seems indeed mandatory to combine thermochemical reactions with non-equilibrium processes such as vertical transport and photochemical processes. The knowledge of the temperature-dependencies, especially at high temperatures, of some key parameters - IR absorption coefficients k λ(T), UV absorption cross-sections σ(T) and chemical kinetics reaction rates k(T) - is also crucial to insure the reliability of hot atmospheres modelling and the interpretation of current observations.