Joint Magnetospheres of Star-planet Systems

The proximity between close-in hot Jupiters and their host star is expected to give rise to star-planet interactions . One signature of such interactions can be the observed phase shift between the location of enhanced chromospheric emission and the orbital phase of the exoplanet. Here, we investigate the magnetic interaction of a hot Jupiter with its magnetically active host star in the framework of a potential magnetic field approximation. The focus of our work is on the structure of the joint magnetosphere of the system, in particular, on the locations of inter-connecting magnetic field flux on the stellar and planetary surfaces. For the host star a realistic magnetic surface map, reconstructed from Zeeman-Doppler imaging observations, is used. The planetary magnetic field is taken to resemble a magnetic dipole perpendicular to the orbital plane. Our results show single- and double-loop magnetic field structures inter-connecting stellar surface regions at different latitudes with opposite polarity regions around the poles of the exoplanet...