Theory of Radio Pulses from Cosmic Ray Air Showers

Abstract

THE recent results of Porter et al.¹ on detectable polarized radio pulses emitted from extensive air showers cast some serious doubt on the validity of the mechanism for coherent emission suggested by Kahn and Lerche². This mechanism concluded, on the basis of a simple model, that the separation of positive and negative charges by the Earth's magnetic field should produce an observable polarized (east–west) radio signal of some 60,000 flux units × µsec at 45 Mc/s for a shower containing some 10⁶ electrons and positrons. The primary cosmic ray particle energy was taken to be about 5 × 10¹⁵ eV. The purpose of this letter is to point out several effects which are ignored in the treatment of Kahn and Lerche which may play a dominant part in modifying both the intensity and polarization of the coherent signal. These are (i) refractive index variations; (ii) Coulomb scattering; (iii) time variation of the shower front.