Ambipolar decay of magnetic field in magnetars and the observed magnetar activities

Abstract

Magnetars are comparatively young neutron stars with ultra-strong surface magnetic field in the range $10^{14-16}$ G. The old neutron stars have surface magnetic field some what less $\sim 10^8$ G which clearly indicates the decay of field with time. One possible way of magnetic field decay is by ambipolar diffusion. We describe the general procedure to solve for the ambipolar velocity inside the star core without any approximation. With a realistic model of neutron star we determine the ambipolar velocity configuration inside the neutron star core and hence find the ambipolar decay rate and time scale which is consistent with the magnetar observations.

12 pages, 4 figures, Accepted for publication in MPLA

References in corpus (3)

• Magnetar superconductivity versus magnetism: neutrino cooling processes
• The relevance of ambipolar diffusion for neutron star evolution
• Two-fluid simulations of the magnetic field evolution in neutron star cores in the weak-coupling regime