Simulated magnetic field expulsion in neutron star cores

Abstract

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 neutron stars, gamma-ray pulsars. We describe, for the first time, the results from self-consistent magneto-thermal simulations considering not only the effects of the Hall-driven field dissipation in the crust, but 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.

Gravitational radiation from neutron stars deformed by crustal Hall drift

“…While the crustal field for both configurations evolves on a time scale of ∼ 10 4 yr into hemispherically asymmetric structures, the core field remains practically unchanged over radio pulsar lifetimes. This has been recently confirmed by Elfritz et al (2016), who performed detailed core field evolution studies. In this current paper, two representatives of these different initial field configurations (which return the same polar cap field structure conducive to radio pulsar emission) are taken as an input to explore their effect on the neutron star deformation.…”

Evolution of the magnetic field in neutron stars

“…(22)]. The vectors ν ν ν α are, in turn, expressed through various chemical potentials and the magnetic field by the formula (30). Thus,Ė B can be calculated (even without knowing the velocity U U U ), provided that these chemical potentials are determined.…”

Post-glitch exponential relaxation of radio pulsars and magnetars in terms of vortex creep across flux tubes

“…Detailed calculations show that interior magnetic field does not decay appreciably until the crustal field is dissipated, i.e. about for 10 6−7 years (Jahan-Miri 2000; Elfritz et al 2016). As for field evolution in connection with the motion of vortex lines, Gügercinoglu & Alpar (2016) have shown that during creep process force exerted by a vortex line to flux tubes during successive encounters is negligible compared to buoyancy and other forces.…”