Physics of star-planet magnetic interactions

Magnetic interactions between a planet and its environment are known to lead to aurorae and shocks in the solar system. The large number of close-in exoplanets that have been discovered so far triggered a renewed interest in understanding magnetic interactions in other star-planet systems. Multiple magnetic effects were then unveiled, such as planet inflation or heating, planet migration, planetary material escape, and even some modifications of the host star apparent activity. Our goal here is to lay out the basic physical principles underlying star-planet magnetic interactions. We first briefly review the hot exoplanets' population as we know it. We then move to a general description of star-planet magnetic interactions, and finally focus on the fundamental concept of Alfvén wings and its implication for exosystems.