Centre de Physique Théorique


Friday 29 November 2019


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Cosmic rays (CR) have a central position in many major astrophysical issues, from the solar system to galaxy clusters. They stand for a testimony on the conditions in the most extreme objects in the Universe and plays a key role in the physics and chemistry of the interstellar medium (ISM), with consequences ranging from star formation and galactic magnetic fields to the production of light elements. Moreover, the CR could carry information on Dark Matter.

The results of observations, accumulated during the past decade, have considerably transformed our knowledge of the CR physics. The level of detail and precision achieved in the direct measurements of CR by the PAMELA, AMS-02, Fermi or Voyager space missions bring remarkable constraints on the propagation models of Galactic CR. The observations from Kaskade-GRANDE and Auger from 10^15 to 10^20 eV enabled us to improve our knowledge on the Galactic-extragalactic transition and on the extreme energy particles. Moreover, if CR generates an incompressible background to neutrino astronomy experiments, the latter have in turn enabled us to measure an anisotropy in the flow of cosmic rays at small and large scales. Such a feature, that still remains to be understood, could notably be connected the microphysics of transport and the properties of the interstellar magnetic field. Finally, the observations of possible high-energy acceleration sites, from X-rays to gamma-rays of high and very high energy, have brought many elements supporting the theories of acceleration. At the same time, several works of numerical simulations have made progress on the microphysics of acceleration. Notwithstanding, several crucial questions still remain, including the exact origin of particles with energy ≥10^15 eV.