Magnetic fields in Accretion Discs around Neutron Stars - Consequences for the change of spin

Abstract

Accretion disks are ubiquitous in the universe and it is generally accepted that magnetic fields play a pivotal role in accretion-disk physics. The spin history of millisecond pulsars, which are usually classified as magnetized neutron stars spun up by an accretion disk, depends sensitively on the magnetic field structure, and yet highly idealized models from the 80s are still being used for calculating the magnetic field components. We present a possible way of improving the currently used models with a semi-analytic approach. The resulting magnetic field profile of both the poloidal and the toroidal component can be very different from the one suggested previously. This might dramatically change our picture of which parts of the disk tend to spin the star up or down.