The cosmic-ray spectrum: From the knee to the ankle

Abstract

This talk addresses the question, «Where is the transition from cosmic rays of galactic origin to extra-galactic cosmic-rays?» I have addressed the background of this topic recently in lectures at Erice and, with Todor Stanev, in a collection of papers on various aspects of nuclear astrophysics. Here I concentrate on primary composition as a signature of the transition and mention some new air-shower experiments aimed at the energy region from the knee to the ankle (PeV to 10 EeV). © © 2006 IOP Publishing Ltd.