CXXIII. Time variations of extensive air showers and the origin of cosmic rays

An experiment is described in which sixteen Geiger counters each of area 200 cm2 arranged on a square lattice of 54 m pitch were used in coincidence to count showers of energies about 1016, 2×1016, 5×1016 and 1017 ev. From the shower rates, no evidence of a deviation from the power law spectrum, R(>E) ∝ E -1·7, was found. The results are analysed in solar and sidereal time. In solar time no variations greater than 1% for the 1016 ev showers or 10% for the 1017 ev showers were found, and these amplitudes could easily arise as a result of statistical fluctuations. In sidereal time, no variation greater than 0·6% was observed at an energy of 1016 ev. At 2×1016 and 5×10 16 ev, small variations were observed which had about 1% chance of being due to random fluctuations. The bearing of these results on theories of the origin of cosmic rays is discussed.