Joint Astrophysics Colloquium

Close-in planets and stellar wind magnetic torques

Antoine Strugarek

Université de Montréal

The diversity of discovered exoplanets in terms of mass, orbit and distance to their host stars promoted a renewed effort of the scientific community on better understanding star-planet interactions (SPI). Close-in planets provide a very interesting natural case of SPI in that their close orbit makes them more exposed to stellar ejecta. Also, they are in some cases likely to orbit inside the stellar wind Alfvèn radius and thus be able to impact their host star global properties (e.g., stellar rotational and/or magnetism evolution history). Among the numerous SPI models which have been developed over the past years, specific magnetohydrodynamic (MHD) simulations have been performed by a few different research groups in order to combine ‘state of the art’ stellar wind numerical models with simplified models of planetary magnetospheres. Because those models are global, they are able to assess both the planetary evolution trends as well as the potential influence of close planets on their host stars self-consistently.

I will present in this talk a parametric study of global magnetic SPI using the PLUTO code. I will distinguish the cases of magnetized and unmagnetized planets, which produce significantly different results, as expected. I will also characterize the potential influence of close-in planets on their host star properties, depending on their orbital position in the stellar wind. Thanks to the versatility of the PLUTO code, I will put a particular emphasis on the influence of various numerical parameters (ideal vs diffusive MHD approaches, boundary conditions choices, numerical methods, magnetic toplogies) on the numerical simulations predictions, and give prescriptions for future magnetized SPI numerical models.