Comment on Japanese Detection of Air Fluorescence Light from a Cosmic Ray Shower in 1969

Abstract

We examine the claim made by Hara et al. in 1969 of the observation of a 10^19 eV cosmic ray extensive air shower using the air fluorescence technique. We find that it is likely that fluorescence light was observed, confirming this as the first such observation. The work of Hara et al. and their friendly competitors at Cornell University paved the way for modern experiments like the Pierre Auger Observatory and the Telescope Array.