An Additional Component Blurring the Transition between Galactic and Extragalactic Cosmic Rays?

Abstract : Recent KASCADE-Grande and Auger results between 1017 eV and 5 1018 eV have revealed complex features in the energy spectrum, be it in the all-particle one or in the composition-sensitive ones. They have also revealed that the mass composition is dominated by iron nuclei around 1017 eV, and by light and intermediate-nuclei elements above 1018 eV. In this contribution, we argue that these results can be interpreted in a coherent way as the manifestation of an additional component of a different origin from the one responsible for the bulk of Galactic cosmic rays. This component, sub-dominant below 1017 eV, appears dominant together with the extragalactic one once the standard Galactic component is extinguished above few 1017 eV, and is responsible for the ankle feature through its rapid suppression above 1018 eV. Possible signatures left in the large-scale structure of arrival directions are discussed.