The influence of the atmospheric refractive index on radio Xmax measurements of air showers
1 Department of Astrophysics/IMAPP, Radboud University, P.O. Box 9010, 6500 GL Nijmegen ( The Netherlands )
2 Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels ( Belgium )
3 Astron, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo ( The Netherlands )
4 Nikhef, Science Park 105, 1098 XG Amsterdam ( The Netherlands )
5 University of California Irvine, Irvine, CA 92697, ( USA )
6 KVI-CART, Zernikelaan 25, 9747 AA Groningen ( The Netherlands )
7 University of Groningen, Zernikelaan 25, 9747 AA Groningen ( The Netherlands )
* e-mail: firstname.lastname@example.org
Published online: 15 March 2017
The refractive index of the atmosphere, which is n ≈ 1:0003 at sea level, varies with altitude and with local temperature, pressure and humidity. When performing radio measurements of air showers, natural variations in n will change the radio lateral intensity distribution, by changing the Cherenkov angle. Using CoREAS simulations, we have evaluated the systematic error on measurements of the shower maximum Xmax due to variations in n. It was found that a 10% increase in refractivity (n – 1) leads to an underestimation of Xmax between 8 and 22 g/cm2 for proton-induced showers at zenith angles from 15 to 45 degrees, respectively.
© The Authors, published by EDP Sciences, 2017
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