On Chern-Simons corrections to magnetohydrodynamics equations

TL;DR

This paper investigates how Chern-Simons electrodynamics modifies magnetohydrodynamics equations, revealing potential astrophysical sources of pseudo-scalar waves in pulsars and magnetars due to these corrections.

Contribution

It introduces Chern-Simons corrections to magnetohydrodynamics equations and explores their implications for magnetic field evolution and pseudo-scalar wave generation in astrophysical objects.

Findings

Chern-Simons corrections produce small source terms for magnetic fields.

Pulsars and magnetars can generate propagating pseudo-scalar waves.

Wave solutions for pseudo-scalar fields are derived in pulsar environments.

Abstract

We study the effect of a (3+1)-dimensional Chern-Simons electrodynamics on the equations governing the dynamics of magnetized plasma and fields. In this model, the Chern-Simons (CS) part consists of a dynamical pseudo-scalar field whose space-time derivatives couple with the electromagnetic field. We explore the CS corrections to the evolution equation for the magnetic field in a plasma with non-zero electrical resistivity. We revisit Cowling's theorem in this context and observe that the CS corrections lead to possibly small but non-zero source terms for axisymmetric magnetic field. The scalar product of electric and magnetic fields play the role of source of the pseudo-scalar field, and therefore, pulsars and magnetars are likely astrophysical candidates to generate propagating pseudo-scalar waves. Although aligned electric field gets shorted out by flowing charges in large parts of the magnetosphere, there are vacuum gaps in the vicinity of pulsars where strong $\vec E. \vec B$ is expected to be present. We derive a wave solution for the pseudo-scalar field generated by the time-varying $\vec E. \vec B$ associated with a pulsar.