A Realistic Treatment of Geomagnetic Cherenkov Radiation from Cosmic Ray Air Showers

TL;DR

This paper models coherent electromagnetic radiation from cosmic ray air showers, emphasizing the impact of a realistic air index of refraction and predicting geomagnetic Cherenkov radiation with a double peak frequency spectrum.

Contribution

It introduces a macroscopic calculation method incorporating realistic air refractive index effects and predicts geomagnetic Cherenkov radiation in air showers.

Findings

Realistic air index significantly affects pulse predictions.

Geomagnetic Cherenkov radiation produces high-frequency signals.

Double peak structure in the frequency spectrum is predicted.

Abstract

We present a macroscopic calculation of coherent electro-magnetic radiation from air showers initiated by ultra-high energy cosmic rays, based on currents obtained from three-dimensional Monte Carlo simulations of air showers in a realistic geo-magnetic field. We discuss the importance of a correct treatment of the index of refraction in air, given by the law of Gladstone and Dale, which affects the pulses enormously for certain configurations, compared to a simplified treatment using a constant index. We predict in particular a geomagnetic Cherenkov radiation, which provides strong signals at high frequencies (GHz), for certain geometries together with "normal radiation" from the shower maximum, leading to a double peak structure in the frequency spectrum. We also provide some information about the numerical procedures referred to as EVA 1.0.