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

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

Rio de Janeiro

Conferencia; 33rd International Cosmic Ray Conference; 2013

International Union of Pure and Applied Physics (IUPAP)

The emission of radio waves from air showers induced by cosmic rays has been attributed to the socalledgeomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiationwhich can be observed with rather simple setups. The direction of the electric field vector induced by thisemission process depends only on the local magnetic field vector and on the arrival direction of the cosmic ray.We report on measurements of the electric field vector where, in addition to this geomagnetic component, anothercomponent has been observed which cannot be described by the geomagnetic emission process. This otherelectric field component has a radial dependence with respect to the shower axis in agreement with predictionsmade by Askaryan using a charge-excess model. Our results are compared to calculations based on models thatinclude the radiation mechanism induced by the charge-excess process.