Ankle-like feature in the energy spectrum of light elements of cosmic rays observed with KASCADE-Grande

Abstract

Recent results of the KASCADE-Grande experiment provided evidence for a mild knee-like structure in the all-particle spectrum of cosmic rays at $E={10}^{16.92\ifmmode\pm\else\textpm\fi{}0.10}\text{ }\text{ }\mathrm{eV}$, which was found to be due to a steepening in the flux of heavy primary particles. The spectrum of the combined components of light and intermediate masses was found to be compatible with a single power law in the energy range from ${10}^{16.3}$ to ${10}^{18}\text{ }\text{ }\mathrm{eV}$. In this paper, we present an update of this analysis by using data with increased statistics, originating both from a larger data set including more recent measurements and by using a larger fiducial area. In addition, optimized selection criteria for enhancing light primaries are applied. We find a spectral feature for light elements, namely, a hardening at $E={10}^{17.08\ifmmode\pm\else\textpm\fi{}0.08}\text{ }\text{ }\mathrm{eV}$ with a change of the power law index from $\ensuremath{-}3.25\ifmmode\pm\else\textpm\fi{}0.05$ to $\ensuremath{-}2.79\ifmmode\pm\else\textpm\fi{}0.08$.