The air shower maximum probed by Cherenkov effects from radio emission

TL;DR

This paper demonstrates that Cherenkov effects significantly influence radio signals from cosmic-ray air showers, enabling more accurate determination of the shower maximum, which is crucial for understanding the primary cosmic ray's mass.

Contribution

It highlights the importance of Cherenkov effects in radio emission models and shows how they improve the extraction of the air shower maximum from radio data.

Findings

Cherenkov effects are crucial for accurate shower maximum measurement.

The relative strength of emission mechanisms varies with observer distance.

Inclusion of Cherenkov effects enhances cosmic ray composition analysis.

Abstract

Radio detection of cosmic-ray-induced air showers has come to a flight the last decade. Along with the experimental efforts, several theoretical models were developed. The main radio-emission mechanisms are established to be the geomagnetic emission due to deflection of electrons and positrons in Earth's magnetic field and the charge-excess emission due to a net electron excess in the air shower front. It was only recently shown that Cherenkov effects play an important role in the radio emission from air showers. In this article we show the importance of these effects to extract quantitatively the position of the shower maximum from the radio signal, which is a sensitive measure for the mass of the initial cosmic ray. We also show that the relative magnitude of the charge-excess and geomagnetic emission changes considerably at small observer distances where Cherenkov effects apply.