Simulated magnetic field expulsion in neutron star cores

The study of long-term evolution of neutron star (NS) magnetic fields is key to understanding the rich diversity of NS observations, and to unifying their nature despite the different emission mechanisms and observed properties. Such studies in principle permit a deeper understanding of the most important parameters driving their apparent variety, e.g. radio pulsars, magnetars, X-ray dim isolated NSs, gamma-ray pulsars. We describe, for the first time, the results from self-consistent magnetothermal simulations considering not only the effects of the Hall-driven field dissipation in the crust, but also adding a complete set of proposed driving forces in a superconducting core. We emphasize how each of these core-field processes drive magnetic evolution and affect observables, and show that when all forces are considered together in vectorial form, the net expulsion of core magnetic flux is negligible, and will have no observable effect in the crust (consequently in the observed surface emission) on megayear time-scales. Our new simulations suggest that strong magnetic fields in NS cores (and the signatures on the NS surface) will persist long after the crustal magnetic field has evolved and decayed, due to the weak combined effects of dissipation and expulsion in the stellar core.

J.G.E. and N.R. are funded by an NWO Vidi grant (PI: Rea). J.A.P. is funded by the grants AYA2013-42184-P and Prometeu/2014/6. N.R. and D.V. acknowledge support from the grants AYA2012-39303 and SGR 2014-1073. K.G. is supported by the Ramón y Cajal Programme of the Spanish Ministerio de Ciencia e Innovación. Authors also wish to acknowledge NewCompStar, COST action MP1304 for partial funding of this research.