Magnetic field decay in young radio pulsars

TL;DR

This paper shows that magnetic field decay in young neutron stars can explain observed anomalies in pulsar braking indices, with decay processes linked to crustal physics and cooling stages.

Contribution

It introduces a model where magnetic field decay in hot young neutron stars accounts for anomalous braking indices, connecting decay timescales to crustal electron scattering.

Findings

Magnetic field decay explains observed braking index anomalies.

Decay occurs within a few hundred thousand years, linked to crustal processes.

Later decay due to impurities is slower and consistent with previous studies.

Abstract

The role of magnetic field decay in normal radio pulsars is still debated. In this paper we present results which demonstrate that an episode of magnetic field decay in hot young neutron stars can explain anomalous values of braking indices recently measured for more than a dozen of sources. It is enough to have few tens of per cent of such hot NSs in the total population to explain observables. Relatively rapid decay operates at ages $\lesssim$~few~$\times100$~kyrs with a characteristic timescale of a similar value. We speculate that this decay can be related to electron scattering off phonons in neutron star crusts. This type of decay saturates as a neutron star cools down. Later on, a much slower decay due to crustal impurities dominates. Finally, we demonstrate that this result is in agreement with our early studies.