Fluctuation studies of large air showers: the water Cerenkov lateral distribution at approximately 100 m from the axis of showers of primary energy Ep⩾1017eV

The lateral distribution of the signal produced in water Cherenkov detectors by the extensive air showers secondary to primaries of 10 17 eV has been predicted to be sensitive to fluctuations in shower development. This sensitivity should be greatest at small axial distances (<100 m) and with the existing array at Haverah Park it is possible to make measurements at such distances in a limited number of events of primary energy >or approximately=10 17 eV. These measurements show evidence of substantial fluctuations from shower to shower which are shown to be correlated with the time structure of the shower front. The implications of this work are discussed in terms of current models of development.