Resistive 2-d MHD simulations of an accretion disk around a weakly magnetized neutron star

We carried out two dimensional high-resolution magnetohydrodynamic (MHD) simulations of an accretion disk around a weakly magnetized neutron star. The effects of general relativity are taken into account by using the pseudo-Newtonian potential. Our simulation deals with the transition layer between the magnetosphere and the disk. When magnetic loops connect the star and the mildly resistive accretion disk, the twist injection from the disk or from the neutron star triggers expansion of the loops. Since the expanding loops prevent inflow toward the magnetic poles of the neutron star, disk matter accumulates on the transition layer. When the magnetic loops are twisted more than a critical angle, magnetic reconnection taking place in the expanding loops channels the accretion flow toward the poles of the neutron star. Such intermittent magnetic reconnections produce a quasi-periodic variation of the accretion flow in the innermost region of the disk.