The theory of radio pulse production in extensive air showers

Abstract

Abstract Radio emission by extensive air showers is analysed in terms of the apparent particle accelerations as seen from the radio receiving aerial. The emission is shown to be associated principally with the transverse deflection of low energy electrons and positrons in the geomagnetic field, but there is also appreciable radiation due to longitudinal accelerations at the beginning and end of the particle tracks. In contrast to the situation with optical Cerenkov radiation, the emission is influenced only slightly by the refractive index of air. The radio pulse waveform consists of an initial sharp pulse ⩾0·01 μsec in duration, followed by a small-amplitude, long-duration tail of opposite sign. The pulse width increases for vertical showers as the distance from the axis increases. The corresponding frequency spectrum is fairly flat, and extends to ~20 Mc/s. The amplitude of the pulse is ~10 μV/m for primary energies ~1016 eV.