Geomagnetic origin of the radio emission from cosmic ray induced air showers observed by CODALEMA

D. Ardouin (1) , A. Belletoile (1, 2) , C. Berat (2) , D. Breton (3) , Didier Charrier (1) , J. Chauvin (2) , M. Chendeb (4) , A. Cordier (3) , S. Dagoret-Campagne (3) , Richard Dallier (1) , L. Denis (5) , C. Dumez-Viou (5) , C. Fabrice (5) , T. Garçon (1) , X. Garrido (3) , N. Gautherot (6) , Thierry Gousset (1) , Ferid Haddad (1) , D.H. Koang (2) , J. Lamblin (1) , Pascal Lautridou (1) , D. Lebrun (2) , A. Lecacheux (7) , François Lefeuvre (8) , Lilian Martin (1) , O. Ravel (1) , E. Meyer (6) , F. Meyer (6) , N. Meyer-Vernet (9) , D. Monnier-Ragaigne (3) , F. Montanet (2) , K. Payet (2) , G. Plantier (4) , Benoît Revenu (1) , C. Riviere (2) , T. Saugrin (1) , A. Sourice (4) , P. Stassi (2) , A. Stutz (2) , S. Valcares (1)

1 SUBATECH - Laboratoire SUBATECH Nantes
2 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
3 LAL - Laboratoire de l'Accélérateur Linéaire
4 GSII - ESEO-GSII
5 USN - Unité Scientifique de la Station de Nançay
6 LAOB - Laboratoire d'astrophysique de l'observatoire de Besançon (UMR 6091)
7 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
8 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
9 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics

The new setup of the CODALEMA experiment installed at the Radio Observatory in Nançay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to ∧ is used which reproduces the angular dependencies of the number of radio events and their electric polarity.

Mots clés: Ultra-High-Energy Cosmic Rays; Extensive Air showers; Radio detection; 96.40.-z; 95.85.Ry; 95.55.Jz

Domaines: Phénomènes cosmiques de haute energie [astro-ph.HE]

D. Ardouin, A. Belletoile, C. Berat, D. Breton, Didier Charrier, et al.. Geomagnetic origin of the radio emission from cosmic ray induced air showers observed by CODALEMA. Astroparticle Physics, 2009, 31 (3), pp.192-200. ⟨10.1016/j.astropartphys.2009.01.001⟩. ⟨hal-00613000⟩