The influence of nondipolar magnetic field and neutron star precession on braking indexes of radiopulsars

TL;DR

This paper explores how nondipolar magnetic fields and neutron star precession can explain anomalous braking index values in radiopulsars, linking magnetic field complexity and precession to changes in current flow and spin-down behavior.

Contribution

It introduces a model connecting neutron star precession and nondipolar magnetic fields to observed braking index anomalies, emphasizing the role of inner gap current variations.

Findings

Precession causes changes in electric current flow in inner gaps.

Nondipolar magnetic fields influence the braking index values.

The model explains anomalous braking indices in radiopulsars.

Abstract

Some of radiopulsars have anomalous braking index values $n = \Omega \ddot{\Omega} / \dot{\Omega}^2 \sim \pm (10^3 \div 10^4) $. It is shown that such values may be related with nondipolar magnetic field. The precession of neutron star lead to rotation (in reference frame related with neutron star) of vector of angular velocity $\vec{\Omega}$ along direction of neutron star magnetic dipole moment $\vec{m}$ with angular velocity $\vec{\Omega}_{p}$. This process may cause the altering of electric current flow through inner gap and consequently the current losses with the same time scale as precession period $T_{p} = 2\pi / \Omega_{p}$. It occurs because of electric current in inner gaps is determined by Goldreich-Julian charge density $\rho_{GJ} = -\frac{\vec{\Omega} \cdot \vec{B}}{2\pi c}$, which are depend on angle between direction of small scale magnetic field and angular velocity $\vec{\Omega}$. It is essential that pulsar tubes nearby neutron star surface are curved. In current paper it is considered the only inner gaps with steady, electron charge limited flow regime.