Transition from Galactic to extragalactic cosmic-rays : implications for the highest energy Galactic cosmic-rays

International audienceIn this contribution, we discuss the transition from galactic to extragalactic cosmic-rays and its implications for the highest energy galactic cosmic-rays. We first review the aspects of extragalactic ultra-high-energy cosmic-ray propagation relevant to the phenomenology of the transition and present different possible interpretations for the "ankle" of the cosmic-ray spectrum. We then discuss the implications of recent cosmic-ray composition related measurements from the Pierre Auger observatory and the KASCADE-Grande experiment. We argue that the interpretation of the ankle as the signature of the transition from galactic to extragalactic cosmic-rays is currently favored by the analyses released by both experiments. We briefly discuss the implications for galactic cosmic-ray sources as well as the forthcoming experiments which should definitely reveal the origin of the ankle of the cosmic-ray spectru