Ohmic decay of magnetic flux expelled from neutron star interiors

Abstract

We study Ohmic diffusion of magnetic flux expelled from the superconducting core of a neutron star to its crust owing to spindown-induced field evolution. We find that Ohmic decay time-scales in the range 10^7.5-10^9 yr obtain for a wide range of crustal temperatures and impurity concentrations for various equation of state models of neutron star matter. This result is in agreement with the Ohmic time-scale that appears to be required to explain observed magnetic field strengths of isolated and binary neutron stars in the spindown-induced magnetic flux expulsion scenario.