The circular polarization in radio emission from extensive air showers

At LOFAR we measure the radio emission from extensive air showers (EAS) in the frequency band of 30 -- 80~MHz in dual-polarized antennas. Through an accurate antenna calibration we can determine the complete set of four Stokes parameters that uniquely determine the linear and circular polarization of the radio signal for an EAS. The observed dependency of the circular polarization on azimuth angle and distance to the shower axis is explained as due to the interfering contributions from the two different radiation mechanisms, a main contribution due to a geomagnetically-induced transverse current and a secondary component due to the Askaryan effect. The measured data show a quantitative agreement with microscopic CORSIKA/CoREAS calculations. Having a very detailed understanding of radio emission from EAS, opens the possibility to use circular polarization as an investigative tool in the analysis of air shower structure, such as for the determination of atmospheric electric fields.

[1]  A. Corstanje,et al.  Thunderstorm electric fields probed by extensive air showers through their polarized radio emission , 2017 .

[2]  P. Schellart,et al.  Measurement of the circular polarization in radio emission from extensive air showers confirms emission mechanisms , 2016, 1611.00758.

[3]  The University of Manchester,et al.  A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations , 2016, Nature.

[4]  T. Huege.  Radio detection of cosmic ray air showers in the digital era , 2016, 1601.07426.

[5]  P. G. Isar,et al.  Energy estimation of cosmic rays with the Engineering Radio Array of the Pierre Auger Observatory , 2015, 1508.04267.

[6]  R. Dallier,et al.  Evidence for the charge-excess contribution in air shower radio emission observed by the CODALEMA experiment , 2015 .

[7]  J. Anderson,et al.  Measuring a Cherenkov ring in the radio emission from air showers at 110-190 MHz with LOFAR , 2014, 1411.6865.

[8]  P. Schellart,et al.  The radio emission pattern of air showers as measured with LOFAR—a tool for the reconstruction of the energy and the shower maximum , 2014, 1411.7868.

[9]  P. Schellart,et al.  Method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles , 2014, 1408.7001.

[10]  P. G. Isar,et al.  Reconstruction of the energy and depth of maximum of cosmic-ray air showers from LOPES radio measurements , 2014, 1408.2346.

[11]  P. Schellart,et al.  Polarized radio emission from extensive air showers measured with LOFAR , 2014, 1406.1355.

[12]  N. T. Thao,et al.  Probing the radio emission from air showers with polarization measurements , 2014 .

[13]  A. D. Jong,et al.  Detecting cosmic rays with the LOFAR radio telescope , 2013, 1311.1399.

[14]  S. Fliescher,et al.  The Pierre Auger Collaboration , 2011 .

[15]  K. D. Vries,et al.  The air shower maximum probed by Cherenkov effects from radio emission , 2013, 1304.1321.

[16]  T. Huege,et al.  Simulating radio emission from air showers with CoREAS , 2013, 1301.2132.

[17]  K. D. Vries,et al.  The Lateral Distribution Function of Coherent Radio Emission from Extensive Air Showers; Determining the Chemical Composition of Cosmic Rays , 2010, 1008.3308.

[18]  O. Scholten,et al.  Macroscopic treatment of radio emission from cosmic ray air showers based on shower simulations , 2007, 0712.2517.

[19]  O. Scholten,et al.  A macroscopic description of coherent geo-magnetic radiation from cosmic-ray air showers , 2007, 0709.2872.

[20]  M. P. van Haarlem,et al.  LOFAR: The Low Frequency Array , 2005 .

[21]  O. Ravel,et al.  Radiodetection of Cosmic Ray Extensive Air Showers: upgrade of the CODALEMA experiment , 2004, astro-ph/0409039.

[22]  G. Askar’yan.  Excess negative charge of an electron-photon shower and its coherent radio emission , 1962 .