Signal Model and Energy Reconstruction for the Radio Detection of Inclined Air Showers in the 50-200 MHz Frequency Band

TL;DR

This paper develops a model for radio emission from inclined cosmic-ray air showers in the 50-200 MHz band, enabling precise energy reconstruction with less than 10% resolution, applicable to large-scale observatories.

Contribution

It adapts an existing signal model to a wider frequency band and demonstrates accurate energy reconstruction for inclined air showers using simulated data.

Findings

Energy resolution < 5% for Pierre Auger Observatory sites

Energy resolution < 10% for GRANDProto300 with noise

Effective energy reconstruction for large arrays with 1 km spacing

Abstract

The radio emission of cosmic-ray air-showers changes significantly depending on parameters like signal frequency, magnetic field configuration and observing altitude. We use CoREAS simulations to adapt an existing signal model for the radio emission of inclined showers in the 30-80 MHz frequency band to the wide 50-200 MHz band. Our model uses a parametrisation of the charge excess fraction to isolate the geomagnetic emission component. We reconstruct the geomagnetic radiation energy by fitting a lateral distribution function, provided by the model, to the geomagnetic energy fluence distribution of the shower. After we correct for the shower geometry and air density, we correlate the radiation energy with the electromagnetic energy of the shower. We show that the method intrinsic energy resolutions < 5% for the sites of the Pierre Auger Observatory and GRANDProto300. For GRANDProto300, we test the reconstruction with simulations of a realistic, sparse antenna grid and with added noise, and find an energy resolution of < 10% with negligible bias. We do a similar study for a much larger array of 10, 000 km2 with 1 km antenna spacing. We find an intrinsic energy resolution of < 10%.