Crust-core interactions and the magnetic dipole orientation in neutron stars

We develop an effective model for a neutron star with a magnetosphere. It takes into account the electromagnetic torques acting on the magnetic dipole, the friction forces between the crust and the core, and the gravitational corrections. Anomalous electromagnetic torques, usually neglected in a rigid star model, here play a crucial role for the alignment of the magnetic dipole. The crust-core coupling time implied by the model is consistent with the observational data and other theoretical estimations. This model describes the main features of the behavior of the magnetic dipole during the life of the star and, in particular, gives a natural explanation for the n < 3 value of the braking index in a young neutron star.