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

THE PIERRE AUGER COLLABORATION (500 AUTHORS IN ALPHABETICAL ORDER); GARCIA, B

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2014 vol. 89 p. 1 - 18

1550-7998

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