Cosmic ray origin: recent developments

Cosmic rays encompass an enormous energy range: 109 eV to at least 3.1020 eV but their origin is still subject to considerable doubt. Progress is being made, however. Erlykin and Wolfendale have drawn attention to structure in the energy spectrum in the range 1015-1016 eV which they attribute to a local recent, supernova. If verified, this will push the subject along considerably. At the very highest energies, above 3 x 1018 eV, where the particles are almost certainly extragalactic, Wibig and Wolfendale have made the case for a significant fraction of the particles being 'heavy' nuclei. An important consequence is that the top-down mechanism (Dark Matter - cryptons - decaying into nucleons and gamma rays) cannot be responsible for all the ultra-energetic particles. Thus, the down-up mechanism will have to be invoked. A leading contender here is galaxy-galaxy collisions. (author)