Timing Noise in Pulsars and Magnetars and the Magnetospheric Moment of Inertia

TL;DR

This paper investigates timing noise in pulsars and magnetars, revealing a magnetic field-dependent component likely caused by variations in the magnetospheric moment of inertia, indicating rapid magnetospheric changes.

Contribution

It introduces the concept of magnetospheric moment of inertia variation as a source of timing noise, distinct from magnetospheric torque effects.

Findings

Timing noise component strongly depends on magnetic field strength.

Smallest observable glitch size correlates with magnetic field.

Magnetospheric torque variation cannot explain the observed timing noise.

Abstract

We examine timing noise in both magnetars and regular pulsars, and find that there exists a component of the timing noise with strong magnetic field dependence above B ~ 10^{12.5} G. The dependence of the timing noise floor on the magnetic field is also reflected in the smallest observable glitch size. We find that magnetospheric torque variation cannot explain this component of timing noise. We calculate the moment of inertia of the magnetic field outside of a neutron star and show that this timing noise component may be due to variation of this moment of inertia, and could be evidence of rapid global magnetospheric variability.