An Estimate of the Spectral Intensity Expected from the Molecular Bremsstrahlung Radiation in Extensive Air Showers

摘要

A detection technique of ultra-high energy cosmic rays, complementary to thefluorescence technique, would be the use of the molecular Bremsstrahlungradiation emitted by low-energy electrons left after the passage of the showersin the atmosphere. The emission mechanism is expected from quasi-elasticcollisions of electrons produced in the shower by the ionisation of themolecules in the atmosphere. In this article, a detailed calculation of thespectral intensity of photons at ground level originating from the transitionsbetween unquantised energy states of free ionisation electrons is presented. Inthe absence of absorption of the emitted photons in the plasma, the obtainedspectral intensity is shown to be 5 10^{-26} W m^{-2}Hz^{-1} at 10 km from theshower core for a vertical shower induced by a proton of 10^{17.5} eV.