CRUSTAL MAGNETIC-FIELD DECAY IN NEUTRON-STARS AND THE NATURE OF SUPERDENSE MATTER

The decay of a magnetic field anchored in the crust of a neutron star strongly depends on the state of the core matter in which the density exceeds that of nuclei. This dependence is a consequence of the temperature dependence of the electrical conductivity and hence the thermal history of the neutron star. The thermal evolution is determined by the properties of high-density core matter. Information about the state of this matter can be obtained from analysis of field decay even when the magnetic field is confined to the surface layers. We compare the field decay for two neutron star cooling models. One model includes only ''standard'' neutrino emissivities; the other presents an example of accelerated cooling by enhanced neutrino emission from the core. Our simulations show a large qualitative difference in evolution of the crustal field for these models, with much less field decay in the case of rapid cooling.