The influence of the atmospheric refractive index on radioX_maxmeasurements of air showers

Abstract

Abstract. 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 X max due to variations in n. It was found that a 10 % increase in refractivity (n − 1) leads to an underestimation of X max between 8 and 22 g/cm 2 for proton-induced showers at zenith angles from 15 to 45 degrees, respectively.