Geomagnetic origin of the radio emission from cosmic ray induced air showers observed by CODALEMA

TL;DR

This paper reports on the CODALEMA experiment's upgraded setup, demonstrating that the radio emission from cosmic ray air showers is primarily due to geomagnetic effects, with observed asymmetries supporting this conclusion.

Contribution

It introduces an upgraded radio and particle detector array at CODALEMA and provides evidence for the geomagnetic origin of radio emissions from air showers.

Findings

Asymmetry in counting rates indicates geomagnetic influence.

Electric field correlates linearly with vxB.

The model reproduces angular dependencies of radio signals.

Abstract

The new setup of the CODALEMA experiment installed at the Radio Observatory in Nancay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to vxB is used which reproduces the angular dependencies of the number of radio events and their electric polarity.