Arrival Directions of Cosmic-Ray Air Showers from the Northern Sky

Abstract

The celestial arrival directions of 2660 air showers of size greater than ${10}^5$ particles at sea level have been determined with an angular resolution of 4°. The observations were made by the method of fast timing, and they cover a band of declination from 10° to 90° north. No significant deviation from isotropy of the primaries of these showers has been found. The response of the array to showers of various sizes and arrival directions has been evaluated theoretically and the results are given. The zenith angle dependence of the counting rate indicates an exponential attenuation with atmospheric depth of the intensity of showers at sea level with an attenuation length of 107±11 g ${\mathrm{cm}}^{-2\mathrm{}}$. As a by-product of the experiment we have found a value for the absolute intensity of showers of size greater than ${10}^5$ particles in the vertical direction at sea level which is (9.6±3.0)×${10}^{-11\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\sec }^{-1\mathrm{}}$ ${\mathrm{sterad}}^{-1\mathrm{}}$.