# The Galaxy in circular polarization: all-sky radio prediction, detection strategy, and the charge of the leptonic cosmic rays

## TL;DR

This paper predicts the all-sky circular polarization of Galactic synchrotron emission using existing data, proposing a detection strategy that could confirm electron dominance in cosmic rays and reveal magnetic structures.

## Contribution

It provides the first all-sky prediction of Galactic circular polarization based on existing measurements, enabling new detection approaches and insights into cosmic ray composition and magnetic fields.

## Key findings

- Predicted Galactic CP map for low frequency radio data
- Detection of CP would confirm electrons as primary cosmic ray leptons
- CP strength relates to magnetic field structures along lines of sight

## Abstract

The diffuse Galactic synchrotron emission should exhibit a low level of diffuse circular polarization (CP) due to the circular motions of the emitting relativistic electrons. This probes the Galactic magnetic field in a similar way as the product of total Galactic synchrotron intensity times Faraday depth. We use this to construct an all sky prediction of the so far unexplored Galactic CP from existing measurements. This map can be used to search for this CP signal in low frequency radio data even prior to imaging. If detected as predicted, it would confirm the expectation that relativistic electrons, and not positrons, are responsible for the Galactic radio emission. Furthermore, the strength of real to predicted circular polarization would provide statistical information on magnetic structures along the line-of-sights.