2011ApJ...729..116K

Three-dimensional resistive magnetohydrodynamic simulations of the magnetic interaction of extrasolar planets with their host stars are performed on the basis of a Weber-Davis model of stellar winds. The free parameters of this model are the stellar magnetic field, the temperature of the corona, and the mass flux and have been fitted in order to theoretically explain the observed phase shifts between the so-called hot spots in the stellar chromospheres and the substellar points for the planets HD 179949 b and υ And b. The relative motion between planet and stellar wind causes perturbations of the stellar magnetic field, which propagate along the Alfvén characteristics toward the star. In a first step it is investigated whether the planet has to be magnetized in order to perturb the magnetic field. The second step consists of time-dependent simulations of the propagation, where the component of the electric current density parallel to the magnetic field is used to trace the perturbation. The simulations confirm the theoretical model for the explanation of the observed phase shifts for both planets.