Studies on some aspects of electromagnetic radiation from extensive air showers

Abstract

The scope of present work encompasses the experimental study of simultaneous emission of radio-pulses from large Extensive Air showers (EAS) at frequency pairs, viz, (2-110) MHz and (9-220) MHz and re-analysis of theoretical calculations. The experiment was carried out at the Cosmic Ray Research Laboratory. Department of Physics, Gauhati University, Assam, India during the period 1982-1985. The EAS detecting system consisted of an array of GM counters. For detection of 2 and 9 MHz frequencies, stacked Yagi antennas were erected. The events were recorded with the help of an automatic recording device. The data were collected from 1982 to 1985. Experimental results and their analysis are presented. In order to make a comparison between the theoretical prediction on radio-field strength and with those of present experimental data, the field strengths were re-calculated theoretically. The present study on radio-emission reveals that radio-pulses are emitted simultaneously at various frequencies by EAS having primary energy Ep gt 1016eV. The field strength of radio-pulses is found to be a decreasing function of frequency Comparison of experimental results with theoretical calculations shows that high frequency (gt80 MHz ) emission mechanisms are completely different from low frequency (lt80 MHz ) emission mechanisms. The experimental study of correlation between radio-pulses at different frequencies also supports the same. The observed high fields at low frequencies (lt20 MHz ) cannot be explained with the help of any one of the existing theories. This calls for further theoretical investigation of low frequency radio-emission.