The cosmic-ray knee and ensuing spectrum seen as a consequence of Bell's self-magnetized SNR shock acceleration process

Abstract

Bell's version of diusiv e shock acceleration in supernova remnants, in which the (highly contorted) magnetic eld is mainly self-generated by the accelerated particles, seems to explain the sharpness of the knee in the cosmic ray spectrum (an eect of the limitation of acceleration in the source), despite contributions from very many supernovae; and the expected knee has a sharp drop near 3 PV rigidity for each nuclear species, and then a lower rounded shoulder extending towards 100 PV contributed by some of the type II SNRs. It is shown that the all- particle ux determined by very dieren t techniques in air shower observations denes a very precise spectrum, below 10 19 eV, and this spectrum is discussed in terms of separate nuclear components of Galactic and extragalactic origin. An extragalactic component with similar source spectrum to the Galactic component is favoured, but a helium/hydrogen mixture and a pure proton ux from the extragalactic sources have dieren t attractions, and oer dieren t tests through composition, even below 10 18 eV. 1. Interpreting the notable features of the cosmic ray spectrum