Evidence for a geomagnetic effect in the CODALEMA radio data

TL;DR

The paper presents evidence that the asymmetry in radio signals from cosmic air showers detected by CODALEMA is primarily due to a geomagnetic effect, confirming the influence of Earth's magnetic field on radio emission.

Contribution

It provides experimental evidence linking the observed asymmetry in radio data to a geomagnetic emission mechanism in cosmic air showers.

Findings

Sky distribution asymmetry explained by geomagnetic emission

Quantitative description of the asymmetry using the cross product model

Supports the geomagnetic origin of radio signals in air showers

Abstract

The CODALEMA experiment detects the cosmic air showers with an hybrid detector composed of an array of scintillators and an array of antennas triggered by the particle array. We will first describe the experiment and the data analysis then we will focus on the sky distribution of the events detected by the antennas which presents a strong asymmetry. We will show that this asymmetry is well described and quantified at first order by an emission of the shower electric field given by the cross product of the shower axis with the geomagnetic field vector. The physical origin of this term is explained in another talk in this conference.