Energy spectrum of cosmic rays as derived from GPS-synchronized EAS array experiments

Using data from 2.5 years of observations with the Large Area Air Shower (LAAS) experiments in Okayama area, we report the cosmic ray energy spectrum obtained by applying cuts on the number of coincidences of 4 extensive air shower (EAS) arrays, which are synchronized by GPS time stamp system with an accuracy of 1 μs.The spectral indices in the energy ranges of 1015 – 1016eV and 1016 – 1018eV are obtained and are consistent with assumed ones within statistical errors. The methods to determine the energy spectrum without evaluating the parameters for each individual EAS in each LAAS array, are reported in this paper. The performances of each single array are simulated as well as those of multiple arrays coincident within a several μs time interval.