An MHD Model of Be Stars with Disks

Abstract An investigation of the formation and evolution of Be stars show that these stars could have dipolar fossil magnetic fields. This magnetic field should constrain the circumstellar magnetic disk and influence its dynamical features. For studying these effects we refine the alphamodel of accretion disks of Shakura and Sunyaev by incorporating into this model the evolution of large-scale magnetic fields. In the frame of our model we can investigate the rotational history of the star with the disk and the ionization and thermal properties of disks. We show in particular that in the magnetopause region a current sheet can form that can generate X-ray radiation.