The Sidereal Correlation of Extensive Air Showers

Abstract

About 3 × 105 extensive air-shower events were recorded at Auckland (altitude 40m, latitude 37° S.) with 3 counter trays at the corners of a 4 m triangle, each of sensitive area 2360 cm2, in the period February 1951 to February 1952. The results show a solar diurnal amplitude of (1.45 ± 0.25)% with maximum at (2.7 ± 0.6) hours local solar time and a sidereal diurnal amplitude of (1.10 ± 0.26)% with maximum at (19.8 ± 0.9) hours local sidereal time (standard errors). By introducing the concept of antisidereal time (there are 364.2 antisidereal days per year) an allowance is made for the seasonal amplitude modulation of the solar diurnal variation. When this correction is applied, the true sidereal diurnal amplitude becomes (1.43 ± 0.38)% with maximum at (17.6 ± 1.0) hours local sidereal time. The results indicate a maximum in the cosmic ray intensity when the galactic plane is overhead.