SO colloquium: Stars and their close-by planets: clues of magnetic interactions

Stars interact with their close-in planets through the gravitational and magnetic fields and with their radiation. After a general introduction to those interactions, I shall review some observational clues of magnetic star-planet interactions considering data obtained in the optical, X-ray, and radio domains. Based on a stellar force-free coronal field or the excitation of Alfven waves by an orbiting planet, some analytical models will be introduced to explore the energetics of the interactions. Some numerical models will be discussed to show their potential and drawbacks in predicting the interactions. The information on stellar magnetic fields that can be derived from magnetic star-planet interactions will be briefly considered and some preliminary results will be presented in the framework of the analytical models.