Burial of the polar magnetic field of an accreting neutron star - II. Hydromagnetic stability of axisymmetric equilibria

Abstract

The theory of polar magnetic burial in accreting neutron stars predicts that a mountain of accreted material accumulates at the magnetic poles of the star, and that, as the mountain spreads equatorward, it is confined by, and compresses, the equatorial magnetic field. Here, we extend previous, axisymmetric, Grad-Shafranov calculations of the hydromagnetic structure of a magnetic mountain up to accreted masses as high as Ma = 6 × 10-4 M⊙, by importing the output from previous calculations (which were limited by numerical problems and the formation of closed bubbles to Ma < 10-4 M⊙) into the time-dependent, ideal-magnetohydrodynamic code ZEUS-3D and loading additional mass on to the star dynam..