Nitrogen fluorescence in air for observing extensive air showers

Abstract

Abstract. Extensive air showers initiate the fluorescence emissions from nitrogen molecules in air. The UVlight is emitted isotropically and can be used for observing the longitudinal development of extensive air showers in the atmosphere over tenth of kilometers. This measurement technique is well-established since it is exploited for many decades by several cosmic ray experiments. However, a fundamental aspect of the air shower analyses is the description of the fluorescence emission in dependence on varying atmospheric conditions. Different fluorescence yields affect directly the energy scaling of air shower reconstruction. In order to explore the various details of the nitrogen fluorescence emission in air, a few experimental groups have been performing dedicated measurements over the last decade. Most of the measurements are now finished. These experimental groups have been discussing their techniques and results in a series of Air Fluorescence Workshops commenced in 2002.At the 8 th Air Fluorescence Workshop 2011, it was suggested to develop a common way of describing the nitrogen fluorescence for application to air shower observations. Here, first analyses for a common treatment of the major dependences of the emission procedure are presented. Aspects like the contributions at different wavelengths, the dependence on pressure as it is decreasing with increasing altitude in the atmosphere, the temperature dependence, in particular that of the collisional cross sections between molecules involved, and the collisional de-excitation by water vapor are discussed.

Open Questions in Cosmic-Ray Research at Ultrahigh Energies

“…TA uses the absolute yield measured by Kakimoto et al (1996) at 337 nm and the wavelength dependence of the fluorescence yield measured by FLASH (Abbasi et al, 2008a). The dependence on atmospheric pressure, temperature, and humidity is treated identically by both collaborations using the reference model formula reported in UHECR2012 (Keilhauer et al, 2013). The corrections for the invisible energy of air showers are based on data in the case of Auger (Aab et al, 2019) and on Monte Carlo simulations in the case of TA.…”

A systematic uncertainty on the energy scale of the Telescope Array fluorescence detectors

“…We call this "Model-K". The ELS result reported in ICRC 2015 [10] shows agreement within 2% to the fluorescence yield of the FLASH experiment [14] and "Model-A" which is the absolute yield measured with the AIRFLY experiment [15,16] and the dependence on pressure, temperature and humidity is taken into account for each spectral line using the reference model formula reported in UHECR2012 [17]. The ELS result shows a 26 % higher result than Model-K and its uncertainty of ELS is quoted as 7.9% [10].…”

Performances of JEM-EUSO: angular reconstruction

“…The fluorescence photons are produced using the photon yield obtained from [Nagano et al 2004]. Even though more recent data could be used, the impact would be negligible to our experiment, since the fluctuations between the different experiments are minor [Keilhauer et al 2013] and out of the scope of our resolution. The atmospheric transfer of the photons is conducted via an approximation.…”