Hot Jupiter accretion: 3D MHD simulations of star-planet-wind interaction

We present 3D MHD simulations of the wind-wind interactions between a solar-type star and a short period hot Jupiter (HJ) exoplanet. This is the first such simulation in which the stellar surface evolution is studied in detail. In our simulations, a planetary outflow, based on models of FUV evaporation of the exoplanets upper atmosphere, results in the build-up of circumstellar and circumplanetary material that accretes on to the stellar surface in a form of coronal rain, in which the rain is HJ wind material falling on to the stellar surface. We have conducted a suite of mixed geometry high-resolution simulations that characterise the behaviour of interacting stellar and planetary wind material for a representative HJ hosting system. Our results show that magnetic topology plays a central role in forming accretion streams between the star and HJ and that the nature of the accretion is variable in both location and rate, with the final accretion point occurring at phi(similar to) = (similar to)227 degrees ahead of the sub-planetary point and 0(similar to) = (similar to)53 degrees below the orbital plain. The size of the accretion spot itself has been found to vary with a period of 67 ks. Within the accretion spot, there is a small decrease in temperature accompanied by an increase in density compared with ambient surface conditions. We also demonstrate that magnetic fields cannot be ignored as accretion is highly dependent upon the magnetic topology of both the HJ and the host. We characterize this behaviour as star-planet-wind interaction.