ABSTRACT
The Cherenkov technique for detecting extensive air showers (EAS) is based on the fact that electrons in EAS generate Cherenkov radiation if their energy exceeds a minimum threshold Emin. The angular distribution of Cherenkov light from an EAS observed at the surface of the Earth is due to the angular spread of the electrons from multiple scattering and to the Cherenkov angle. The Cherenkov angular cone is smaller at higher elevations since the index of refraction of the atmosphere is larger. Because of this variation, Cherenkov light generated from heights of between seven to 20 kilometers above sea level would fall within a ring of 110 to 145 meters in radius from the shower core if electrons did not multiple scatter. The primary particle energy is generally determined by estimating the total Cherenkov light flux at the observation surface Ф.
