Influence of Atmospheric Electric Fields on the Radio Emission from Extensive Air Showers

TL;DR

This paper investigates how atmospheric electric fields influence the radio signals from extensive air showers, revealing non-linear effects and enhanced sensitivity at lower frequencies through simulations and simplified models.

Contribution

It provides a new explanation for the non-linear dependence of radio signal strength on electric fields and suggests extending frequency observations to improve atmospheric electric field detection.

Findings

Radio signal strength depends non-linearly on electric field magnitude.

Lower frequency observations increase sensitivity to atmospheric electric fields.

Simulations and simplified models explain electron dynamics in air showers.

Abstract

The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. Simulations indicated a very non-linear dependence of the signal strength in the frequency window of 30-80 MHz on the magnitude of the atmospheric electric field. In this work we present an explanation of this dependence based on Monte-Carlo simulations, supported by arguments based on electron dynamics in air showers and expressed in terms of a simplified model. We show that by extending the frequency window to lower frequencies additional sensitivity to the atmospheric electric field is obtained.