# Thunderstorm electric fields probed by extensive air showers through their polarized radio emission

## TL;DR

This study uses polarized radio emissions from extensive air showers to probe electric fields in thunderstorms, revealing significant circular polarization changes linked to atmospheric electric field variations.

## Contribution

It demonstrates how polarization measurements of air showers can be used to characterize electric fields in thunderclouds, providing a novel remote sensing method.

## Key findings

- High circular polarization in thunderstorms compared to fair weather
- Electric field changes explain polarization patterns
- Large horizontal electric field components detected

## Abstract

We observe a large fraction of circular polarization in radio emission from extensive air showers recorded during thunderstorms, much higher than in the emission from air showers measured during fair-weather circumstances. We show that the circular polarization of the air showers measured during thunderstorms can be explained by the change in the direction of the transverse current as a function of altitude induced by atmospheric electric fields. Thus by using the full set of Stokes parameters for these events, we obtain a good characterization of the electric fields in thunderclouds. We also measure a large horizontal component of the electric fields in the two events that we have analysed.