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

THE PIERRE AUGER COLLABORATION (AUTOR 434 DE 474); M. TUEROS

Rio de Janeiro

Conferencia; 33rd International Cosmic Ray Conference (ICRC 2013); 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 so-called geomagnetic 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 this emission 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, another component has been observed which cannot be described by the geomagnetic emission process. This other electric field component has a radial dependence with respect to the shower axis in agreement with predictions made by Askaryan using a charge-excess model. Our results are compared to calculations based on models that include the radiation mechanism induced by the charge-excess process.