A study on the emission of electromagnetic waves from large EAS

Abstract

The present work is on the study of the Electromagnetic radiations associated with Extensive Air Showers (EAS). The experiment was carried out at the Cosmic Ray Research Laboratory of the Gauhati University, Assam, India. The experiment was conduc-ted from 1983 to 1987 in winter at selected nights. The first phase of the work was to set up an array of plastic scintillation detectors for the EAS particles. This involved the design, fabrica-tion and calibration of the associated electronics. The most important part of this work is that the new set up consisted of fast electronic circuitry using CMOS ICs, MOSFETs and the microprocessor-based control of the recording of analog scintillation, radio and Cerenkov pulses, their digitization and storing. The installation and calibration of the set up took about one and a half years. The data were collected from the middle of 1984 to the early part of 1987 at selected nights, particularly in the months of winter. The location of the core, the estimation of the shower size and the study of the lateral distribution of the electrons added new dimensions to the works on the EAS studies done at this laboratory so far. Along with the above mentioned parameters of EAS, the emission of the electromagnetic radiations at 9 MHz and 110 MHz and the associated Cerenkov emissions were investigated. The present study on the electromagnetic radiation at radio frequencies reveals that the simultaneous emission of radio pulses at different frequencies are associated with EAS having primary energy E gtp1016 eV. The field strength of radio-pulses is found to decrease with increasing frequencies. Even after determination of the shower core, it is found that high frequency (gt80 MHz) emission mechanism, somehow, can be explained with the existing theory, but the experimental results on radio emission at low frequen-cies (lt10MHz) can not be explained with the existing theory. Perhaps, the low frequency emission mechanism is completely different from that on high frequencies. This needs further...