2012 Volume 67 Issue 12 Pages 832-837
The origin of cosmic rays has been attracting many scientists. The energy spectrum of cosmic rays is a power-law form covering an energy range of 10 decades and has three structures around 10^<15.5>eV, 10^<18.5>eV and 10^<19.5>eV. Moreover, recently, a new structure around 1011 eV was found. We have been puzzled, for a hundred years since the discovery of cosmic rays, how the spectrum is produced, where and how cosmic rays are accelerated, and so on. In this paper, we introduce a part of 100-year struggle for understanding cosmic rays.