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

TL;DR

This paper provides a detailed calculation of the spectral intensity of molecular Bremsstrahlung radiation expected from extensive air showers, offering a potential method for ultra-high energy cosmic ray detection.

Contribution

It introduces a comprehensive model for estimating the spectral intensity of molecular Bremsstrahlung radiation in air showers, advancing detection techniques for cosmic rays.

Findings

Spectral intensity at 10 km from shower core is approximately 5×10^{-26} W/m^2/Hz.

Emission mechanism is based on quasi-elastic collisions of ionisation electrons.

Results suggest potential for detecting ultra-high energy cosmic rays via this radiation.

Abstract

A detection technique of ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy electrons left after the passage of the showers in the atmosphere. The emission mechanism is expected from quasi-elastic collisions of electrons produced in the shower by the ionisation of the molecules in the atmosphere. In this article, a detailed calculation of the spectral intensity of photons at ground level originating from the transitions between unquantised energy states of free ionisation electrons is presented. In the absence of absorption of the emitted photons in the plasma, the obtained spectral intensity is shown to be 5 10^{-26} W m^{-2}Hz^{-1} at 10 km from the shower core for a vertical shower induced by a proton of 10^{17.5} eV.