− excesses and the knee of the cosmic rays — hints of cosmic rays acceleration at young supernova remnant

Supernova remnants have long been regarded as sources of the Galactic cosmic rays up to petaelectronvolts, but convincing evidence is still lack. Considering the ee pair production via interactions between high energy cosmic rays and background photons in an environment like the young supernova remnant, we explore the common origin of the subtle features of the cosmic rays spectra, such as the knee of cosmic rays and the excesses of electrons/positrons recently observed by ATIC, H.E.S.S., Fermi-LAT and PAMELA. Numerical calculation shows that those features of cosmic rays spectra can be well reproduced in this picture. The success of such a coherent explanation serves in turn as an evidence that at least a portion of cosmic rays might be accelerated at young supernova remnants. Subject headings: cosmic rays — supernova remnants — acceleration of particles Ever since the discovery made by Kulikov and Kristiansen in 1958 (Kulikov & Kristiansen 1958), the knee of the cosmic ray (CR) spectrum at an energy around 4 PeV has kept being a puzzle for half a century. The origin of the knee has become a key problem of CR physics, as it is closely related to the acceleration of the Galactic CRs. There have been extensive studies on the issue (e.g., see the review of Höorandel (2006) and references therein), however, no consensus has been reached yet due to the lack of high precision experimental information. Recently, the ATIC experiment measured the cosmic electron (including positron) spectrum up to several TeV (Chang et al. 2008) with high precision and discovered an obvious excess. In addition, the ground based atmospheric Cerenkov telescope H.E.S.S. and the space satellite Fermi, which are dedicated to detect the high energy γ-rays, also reported their results on the electron spectrum measurements (Fermi-LAT Collaboration 2009; Aharonian et al. 2008; H. E. S. S. Collaboration 2009). There are still some differences between the results of ATIC and Fermi, however, both of them seem to show the excess