Probing the radio emission from cosmic-ray-induced air showers by polarization measurements

THE PIERRE AUGER COLABORATION; C. JARNE

PHYSICAL REVIEW D - PARTICLE AND FILDS

AMER PHYSICAL SOC

Año: 2014 p. 1 - 18

0556-2821

The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be observed with rather simple setups. The direction of the electric eld induced by this emission process depends only on the local magnetic eld vector and on the incoming direction of the air shower. We report on measurements of the electric eld vector where, in addition to this geomagnetic component, another component has been observed which cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric eld component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge-excessin the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.