Temperature and Humidity Dependence of Air Fluorescence Yield measured by AIRFLY

TL;DR

This study investigates how temperature and humidity affect air fluorescence yield, crucial for cosmic ray detection, revealing up to 20% variations that must be considered for accurate energy measurements.

Contribution

It provides detailed measurements of temperature and humidity effects on nitrogen fluorescence emission relevant for cosmic ray air shower analysis.

Findings

Temperature and humidity significantly affect fluorescence yield.

Up to 20% variation in fluorescence yield due to atmospheric conditions.

Results are specific to key nitrogen emission bands.

Abstract

The fluorescence detection of ultra high energy cosmic rays requires a detailed knowledge of the fluorescence light emission from nitrogen molecules over a wide range of atmospheric parameters, corresponding to altitudes typical of the cosmic ray shower development in the atmosphere. We have studied the temperature and humidity dependence of the fluorescence light spectrum excited by MeV electrons in air. Results for the 313.6 nm, 337.1 nm, 353.7 nm and 391.4 nm bands are reported in this paper. We found that the temperature and humidity dependence of the quenching process changes the fluorescence yield by a sizeable amount (up to 20%) and its effect must be included for a precise estimation of the energy of ultra high energy cosmic rays.