Force-free pulsar magnetosphere: instability and generation of MHD waves

TL;DR

This paper investigates the instability caused by differential rotation in force-free pulsar magnetospheres, revealing that such configurations are inherently unstable with potential impacts on emission fluctuations and magnetospheric diffusion.

Contribution

It provides a linear stability analysis showing that differential rotation leads to instability in force-free pulsar magnetospheres regardless of magnetic field geometry.

Findings

Differentially rotating magnetospheres are unstable for any magnetic field configuration.

The growth time of the instability is approximately the rotation period.

Instability may cause emission fluctuations and increased diffusion in the magnetosphere.

Abstract

Magnetohydrodynamic (MHD) instabilities can play an important role in the structure and dynamics of the pulsar magnetosphere. We consider the instabilitycaused by differential rotation that is suggested by many theoretical models. Stability is considered by means of a linear analysis within the frane of the force-free MHD. We argue that differentially rotating magnetospheres are unstable for any particular geometry of the magnetic field and rotation law. The characteristic growth time of instability is of the order of the rotation period. The instability can lead to fluctuations of the emission and enhancement of diffusion in the magnetosphere.