Probing the radio emission from air showers with polarization measurements

THE PIERRE AUGER OBSERVATORY (PATRICIA HANSEN PERTENECE A LA COLABORACION)

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2014 vol. 1 p. 1 - 12

1550-7998

The emission of radio waves from air showers has been attributed to the so-called geomagneticemission process. At frequencies around 50 MHz this process leads to coherent radiation whichcan be observed with rather simple setups. The direction of the electric eld induced by thisemission process depends only on the local magnetic eld vector and on the incoming directionof the air shower. We report on measurements of the electric eld vector where, in addition tothis geomagnetic component, another component has been observed which cannot be described bythe geomagnetic emission process. The data provide strong evidence that the other electric eldcomponent is polarized radially with respect to the shower axis, in agreement with predictions madeby 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 radiationmechanism induced by this charge-excess process.