Electromagnetic interaction of a magnetized rotating star with a   conducting disk
  A conducting disk significantly changes the generation of the electromagnetic radiation excited by the rotation of the magnetic field frozen to a star. Due to the reflection of waves from a disk there appear waves propagating toward a star, not only outward a star as it takes place for the magneto-dipole radiation. Because that the angular momentum can be transformed from a disk to a star when the inner edge of a disk approaches the light surface of a rotating star. This is purely electromagnetic effect. At some distance of a disk from a star, $r_d=r^*\simeq c/\omega_s$, the stellar angular momentum losses due to the electromagnetic radiation become zero. It results the stable stellar rotation. 
Ya.N Istomin
astro-ph.SR