Polarization properties of turbulent synchrotron bubbles: an approach based on Chandrasekhar-Kendall functions

TL;DR

This paper introduces a new formalism using Chandrasekhar-Kendall functions to analyze the polarization properties of turbulent synchrotron bubbles, accounting for their geometry and linking observable features to magnetic field structures.

Contribution

It presents a novel approach to study synchrotron bubble polarization by incorporating bubble geometry and turbulence spectra, improving interpretation of observational data.

Findings

Provides fitting formulas relating observed polarization to magnetic field structure.

Shows how turbulence spectra and magnetic helicity influence polarization properties.

Extends analysis beyond standard Cartesian domain assumptions.

Abstract

Synchrotron emitting bubbles arise when the outflow from a compact relativistic engine, either a Black Hole or a Neutron Star, impacts on the environment. The emission properties of synchrotron radiation are widely used to infer the dynamical properties of these bubbles, and from them the injection conditions of the engine. Radio polarization offers an important tool to investigate the level and spectrum of turbulence, the magnetic field configuration, and possibly the degree of mixing. Here we introduce a formalism based on Chandrasekhar-Kendall functions that allows us to properly take into account the geometry of the bubble, going beyond standard analysis based on periodic cartesian domains. We investigate how different turbulent spectra, magnetic helicity and particle distribution function, impact on global properties that are easily accessible to observations, even at low resolution, and we provide fitting formulae to relate observed quantities to the underlying magnetic field structure.