Filamentary jets as a cosmic-ray "Zevatron"
  Strong, anisotropic turbulence reflecting magnetized filaments is considered, to model the diffusive acceleration of particles by shock waves in active galactic nucleus jets. We address that at knot A of the nearby M87 jet, the shock involving the filamentary turbulence can accelerate an iron nucleus to zetta-eV (ZeV; 10^{21} eV) ranges. A smaller value of the particle diffusion coefficient is found to be essential to achieve a ZeV cosmic-ray accelerator, a "Zevatron." 
Mitsuru Honda and Yasuko S. Honda