Considerations on the radio emission from extended air showers

TL;DR

This paper reviews the understanding of radio emissions from cosmic ray air showers, discusses the potential role of bremsstrahlung radiation in the 1-10 GHz range, and proposes an experiment to test its detectability for gamma-ray astronomy.

Contribution

It introduces the idea that bremsstrahlung radiation could be detectable in air showers and proposes an experimental scheme to verify this, potentially impacting gamma-ray astronomy.

Findings

Radio emission from air showers is well understood and scales quadratically with energy.

Bremsstrahlung radiation exists but has not been detected in air showers.

Proposes an experiment to detect bremsstrahlung in the 1-10 GHz range.

Abstract

The process of radio emission from extended air showers produced by high energy cosmic rays has reached a good level of comprehension and prediction. It has a coherent nature, so the emitted power scales quadratically with the energy of the primary particle. Recently, a laboratory measurement has revealed that an incoherent radiation mechanism exists, namely, the bremsstrahlung emission. In this paper we expound why bremsstrahlung radiation, that should be present in showers produced by ultra high energy cosmic rays, has escaped detection so far, and why, on the other side, it could be exploited, in the 1--10~GHz frequency range, to detect astronomical $\gamma$-rays. We propose an experimental scheme to verify such hypothesis, which, if correct, would deeply impact on the observational $\gamma$-ray astronomy.