The Energy Spectrum of Extensive Air Showers

Abstract

The integral shower density spectrum from 20-1000 particles per square metre is measured with three-fold proportional counters 60 metres above sea level, and follows a law ν(ρ) = 540 ρ-1 39±0.04 h-1, for ρ 500 the exponent increases quickly, reaching 2.2 at ρ = 1000, which is typical of the value observed with ionization chambers. The density spectrum is analysed, allowing for effects of shower age on structure to obtain the distribution in number S(N) = 2.3 × 10-4 (N × 10-6)-1 47±0 1 m-2 h-1, with evidence for a rapid increase in exponent above N = 106 particles. Using cascade theory the latter is shown to be produced by a primary energy spectrum V(E) = 0.32 (E × 10-14)-1 5 m-2 h-1 sterad-1, for 1013 < E < 1015, above which the exponent increases rapidly, reaching about -3 at E = 1017 eV. Since shower primaries of these energies should be little affected by solar or terrestrial magnetic fields, this will be the form of the primary spectrum.