Simulating the Three-Dimensional Upper Atmospheres of Close-In Exoplanets with Strong Magnetic Fields

In this investigation, we present 3-D simulations of the upper thermosphere and ionosphere of the Hot Jupiter HD 209458 b (nicknamed Osiris). We examine the 3-D neutral and ion dynamics under the influence of Jovian-type magnetic fields and compare these with a non-magnetic case. Our initial results suggest that the Jovian-type magnetic field significantly reduces the ability of the ions to escape at low-to-mid latitudes, and therefore limits the adiabatic cooling associated with this escape. Thus, the magnetized case exhibits strong escape from the high-latitude polar regions, but significantly reduced escape over the lower latitudes. This configuration results in a significantly warmer global thermosphere in the magnetized case with an energy balance that is driven primarily by Stellar EUV/XUV heating and radiative cooling, which contrasts with the typical non-magnetized case of stellar heating balanced by the adiabatic cooling associated with bulk atmospheric escape.