Lateral Distribution of the Radio Signal in Extensive Air Showers Measured with LOPES

TL;DR

This study analyzes the lateral distribution of radio signals in extensive air showers using LOPES, revealing exponential profiles with some flattening near the shower axis, and suggests the intrinsic nature of these profiles for radio detection.

Contribution

It provides detailed measurements of the lateral distribution of radio signals in air showers and shows that these profiles are intrinsic, supporting large-scale radio detection methods.

Findings

Lateral distributions follow an exponential function.

Approximately 20% of events show flattening near the shower axis.

No correlation between R0 and shower parameters was found.

Abstract

The antenna array LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from Extensive Air Showers. The coincident measurements allow us to reconstruct the electric field strength at observation level in dependence of general EAS parameters. In the present work, the lateral distribution of the radio signal in air showers is studied in detail. It is found that the lateral distributions of the electric field strengths in individual EAS can be described by an exponential function. For about 20% of the events a flattening towards the shower axis is observed, preferentially for showers with large inclination angle. The estimated scale parameters R0 describing the slope of the lateral profiles range between 100 and 200 m. No evidence for a direct correlation of R0 with shower parameters like azimuth angle, geomagnetic angle, or primary energy can be found. This indicates that the lateral profile is an intrinsic property of the radio emission during the shower development which makes the radio detection technique suitable for large scale applications.