Extra-Solar Planetary Atmospheres and Interior Structure: Implications for Observational Signatures

Abstract

Hot Jupiter exoplanets are a previously unknown and fascinating field of study. Models of planet formation based only around the Solar System did not predict their existence, occupying as they do the orbital region less than 0.1 AU from their parent stars. Believed to be tidally locked, always presenting the same face to the star, these gas giants are bathed in intense irradiation, and inhabit a regime alien to anything known in the Solar System. As exoplanetary surveys discover an increasing number of planets, the ubiquity of hot Jupiters in the galaxy continues to be confirmed. Both the evolution and the atmospheric dynamics of these unusual planets are natural focuses of study. However, most authors have historically concentrated on one or the other of these two lines of enquiry, although both are linked. In the case of gas giants in particular, which have no true ground or otherwise easily defined surface layer, the two regimes blend towards the outer layers of the planet. This convergence renders the possibility of model overlap ever more relevant, a possibility that is here studied, both independently and together, ultimately continuing to the modelling of the specific known exoplanets HD 209458b, HD 189733b, and WASP-7b. It is found that, while it is reasonable for interior evolution model results to be used to provide boundary conditions and atmospheric characteristics for the purposes of three-dimensional atmospheric modelling, the reverse is a much more difficult proposition, providing few truly relevant constraints. Observational characteristics are also predicted, with cyclic variability found in the case of HD 209458b, a more permanently variable state in the case of HD 189733b, and very little longitudinal temperature variation for the calmer atmosphere of WASP-7b.