Magnetic diffusion effects on the ultra-high energy cosmic ray spectrum and composition
- CONICET, Centro Atómico Bariloche, Av. Bustillo 9500 (8400) (Argentina)
We discuss the effects of diffusion of high energy cosmic rays in turbulent extra-galactic magnetic fields. We find an approximate expression for the low energy suppression of the spectrum of the different mass components (with charge Z) in the case in which this suppression happens at energies below ∼ Z EeV, so that energy losses are dominated by the adiabatic ones. The low energy suppression appears when cosmic rays from the closest sources take a time comparable to the age of the Universe to reach the Earth. This occurs for energies E < Z EeV (B/nG)√(l{sub c}/Mpc)(d{sub s}/70Mpc) in terms of the magnetic field RMS strength B, its coherence length l{sub c} and the typical separation between sources d{sub s}. We apply this to scenarios in which the sources produce a mixed composition and have a relatively low maximum rigidity (E{sub max} ∼ (2–10)Z EeV), finding that diffusion has a significant effect on the resulting spectrum, the average mass and on its spread, in particular reducing this last one. For reasonable values of B and l{sub c} these effects can help to reproduce the composition trends observed by the Auger Collaboration for source spectra compatible with Fermi acceleration.
- OSTI ID:
- 22282639
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2013, Issue 10; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
Similar Records
Anisotropy vs chemical composition at ultra-high energies
Constraining primordial magnetic fields with distortions of the black-body spectrum of the cosmic microwave background: pre- and post-decoupling contributions