Transition from Galactic to Extragalactic Cosmic Rays
Journal article, Peer reviewed
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Original versionThe European Physical Journal Conferences. 2019, 210 . 10.1051/epjconf/201921004003
The question at which energy the transition from Galactic to extragalactic cosmic rays takes place has been a long-standing conundrum in cosmic ray physics. In the past, the transition energy has been usually associated with one of the evident features of the cosmic ray spectrum: The second knee around E≃5 ×1017 eV or the ankle at E≃3 ×1018 eV. I review anisotropy and composition data and show that they require that the transition from Galacticto extragalactic CRs has to happen early, at few ×1017 eV. As a result, a successful model for the transition should explain the ankle as a feature of the extragalactic CR spectrum. I review briefly such models and their implications.