The physics of strongly irradiated extrasolar planet thermospheres

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At Hamburg Observatory we have developed an extensive simulation tool called TPCI ("The PLUTO-CLOUDY Interface'') to study radiation-hydrodynamical problems. TPCI basically provides an interface between PLUTO, i.e., a code to solve (magneto-)hydrodynamic problems, and CLOUDY, a code that solves the microphysical equilibrium state of a gas, given a certain radiation field. TPCI is an extremely useful tool to study the problem of exoplanetary atmospheres irradiated from the host star with its high-energy radiation. Some part of this impinging radiation will be absorbed, causing heating and expansion of the whole atmosphere, which can ultimately lead to substantial mass outflow in the form of a hydrodynamic wind, somewhat similar to the solar wind acceleration as originally proposed by Parker. The essential new feature about TPCI is that the net heating of the irradiated planetary atmosphere is self-consistently computed by the microphysics solver, and not prescribed in an ad-hoc fashion as done in all previous work. Within the context of this application we want to harvest on our previous efforts by both expanding TPCI throught the inclusion of a treatment of metals and molecules and by applying TPCI to further study a variety of physical problems encountered in irradiated extrasolar planet thermospheres. Specifically, we want to apply our new modelling tool to compute the expected absorption signals due to extrasolar planets during transits and compare our model computations to actual observations, we plan to study the influence of superflares on the atmospheric escape from "Hot Jupiters'' and further characterise the transition from hydrodynamically escaping atmospheres to stable thermospheres.