Radioelectric Field Features of Extensive Air Showers Observed with   CODALEMA
  Based on a new approach to the detection of radio transients associated with extensive air showers induced by ultra high energy cosmic rays, the experimental apparatus CODALEMA is in operation, measuring about 1 event per day corresponding to an energy threshold ~ 5. 10^16 eV. Its performance makes possible for the first time the study of radio-signal features on an event-by-event basis. The sampling of the magnitude of the electric field along a 600 meters axis is analyzed. It shows that the electric field lateral spread is around 250 m (FWHM). The possibility to determine with radio both arrival directions and shower core positions is discussed. 
D. Ardouin, A. Belletoile, D. Charrier, R. Dallier, L. Denis, P.   Eschstruth, T. Gousset, F. Haddad, J. Lamblin, P. Lautrid...