Influence of the Earth's Magnetic Field on Air Showers

Cocconi has estimated that the deflection of air shower particles in the earth's magnetic field should produce some ellipticity of shower structure, with the major axis in the E-W direction. Experimental evidence is advanced to show that the variation in shower structure at sea level is less than 4%, which compares favorably with Cocconi's theoretical value of \ensuremath{\sim}2% and proves that, at low altitudes, the displacement of particles from the shower axis produced by the earth's magnetic field is negligible in comparison with Coulomb scattering.