Photoevaporative Flows From Exoplanet Atmospheres: A 3-D Radiative Hydrodynamic Parameter Study

Abstract

The photoionization-driven evaporation of planetary atmospheres has emerged as a potentially fundamental process for planets on short period orbits. While 1-D studies have proven the effectiveness of stellar fluxes at altering the atmospheric mass and composition for sub-Jupiter mass planets, there remains much that is uncertain with regard to the larger-scale, multidimensional nature of such "planetary wind" flows. In this paper we use a new radiation-hydrodynamic platform to simulate atmospheric evaporative flows. Using the AstroBEAR AMR multiphysics code in a co-rotating frame centered on the planet, we model the transfer of ionizing photons into the atmosphere, the subsequent launch of the wind and the wind's large scale evolution subject to tidal and non-inertial forces. We run simulations for planets of 0.263 and 0.07 Jupiter masses and stellar fluxes of $2 \times 10^{13}$ and $2 \times 10^{14}$ photons/cm^2/s. Our results reveal new, potentially observable planetary wind flow patterns, including the development, in some cases, of an extended neutral tail lagging behind the planet in its orbit.