On the production mechanism of MF-HF radiopulses associated with large extensive air showers

Summary The existing theories on radio-emission from extensive air showers (EAS) are inadequate to explain the observed high fields associated with the emission of LF-MF-HF radiopulses. One of the attempts has been to explain the phenomenon in the light of the transition radiation (TR) mechanism from the excess negative charge of EAS on striking the ground. However, experimental data are very meagre. In order to concretise the theoretical basis of LF-MF-HF emission, experimental investigations on different aspects of radio-emission are essential. The present paper reports the experimental studies on radio-emission at some preselected frequencies (LF-HF) using a sophisticated data acquisition system. Results on i) variation of field strength with age parameter (S) for different primary energies (E _p) and different core distance (R), ii) lateral distribution of field strength for differentE _p andS and iii) frequency spectrum of radio-emission, are presented and analysed in the light of the TR mechanism.