Non-Universal Spectra of Ultra-High Energy Cosmic Ray Primaries and Secondaries in a Structured Universe

Abstract

Analytical calculations of extra-galactic cosmic ray spectra above ~10^17 eV are often performed assuming continuous source distributions, giving rise to spectra that depend little on the propagation mode, be it rectilinear or diffusive. We perform trajectory simulations for proton primaries in the probably more realistic case of discrete sources with a density of ~10^-5/Mpc^3. We find two considerable non-universal effects that depend on source distributions and magnetic fields: First, the primary extra-galactic cosmic ray flux can become strongly suppressed below a few 10^18 eV due to partial confinement in magnetic fields surrounding sources. Second, the secondary photon to primary cosmic ray flux ratio between ~3x10^18 eV and ~10^20 eV decreases with decreasing source density and increasing magnetization. As a consequence, in acceleration scenarios for the origin of highest energy cosmic rays the fraction of secondary photons may be difficult to detect even for experiments such as Pierre Auger. The cosmogenic neutrino flux does not significantly depend on source density and magnetization.

arXiv comment9 revtex pages, 9 figures, published version, minor changes

References in corpus (46)

• Origin and Propagation of Extremely High Energy Cosmic Rays
• On astrophysical solution to ultra high energy cosmic rays
• Constrained Simulations of the Magnetic Field in the Local Universe and the Propagation of UHECRs
• Measurement of the Flux of Ultrahigh Energy Cosmic Rays from Monocular Observations by the High Resolution Fly's Eye Experiment
• Cosmological Magnetic Fields Limits in an Inhomogeneous Universe
• Dip in UHECR spectrum as signature of proton interaction with CMB
• Measurement of the Cosmic Ray Energy Spectrum and Composition from 10^{17} to 10^{18.3} eV Using a Hybrid Fluorescence Technique
• A Study of the Composition of Ultra High Energy Cosmic Rays Using the High Resolution Fly's Eye
• A new estimate of the extragalactic radio background and implications for ultra-high-energy gamma-ray propagation
• Ultra-High Energy Cosmic Ray Probes of Large Scale Structure and Magnetic Fields
• Models of the Knee in the Energy Spectrum of Cosmic Rays
• A dip in the UHECR spectrum and the transition from galactic to extragalactic cosmic rays
• UHE nuclei propagation and the interpretation of the ankle in the cosmic-ray spectrum
• Inter-galactic Shock Acceleration and the Cosmic Gamma-ray Background
• Extra-galactic magnetic fields and the second knee in the cosmic-ray spectrum
• An upper limit to the photon fraction in cosmic rays above 10^19 eV from the Pierre Auger Observatory
• Cosmogenic Neutrinos from Ultra-High Energy Nuclei
• Diffusive propagation of UHECR and the propagation theorem
• The Impact of Heavy Nuclei on the Cosmogenic Neutrino Flux
• GZK Photons as Ultra High Energy Cosmic Rays
• Mapping deflections of extragalactic Ultra-High Energy Cosmic Rays in magnetohydrodynamic simulations of the Local Universe
• Reconciling the ultra-high energy cosmic ray spectrum with Fermi shock acceleration
• High-energy neutrinos from astrophysical accelerators of cosmic ray nuclei
• Upper limit on the ultra-high-energy photon flux from AGASA and Yakutsk data
• Anti-GZK effect in Ultra High Energy Cosmic Rays diffusive propagation
• Upper limit on the photon fraction in highest-energy cosmic rays from AGASA data
• Observational Gamma-ray Cosmology
• CRPropa: A Numerical Tool for the Propagation of UHE Cosmic Rays, Gamma-rays and Neutrinos
• Diffusion of Cosmic Rays in the Expanding Universe. II. Energy Spectra of Ultra-High Energy Cosmic Rays
• The highest-energy cosmic rays
• Extragalactic Magnetic Field and the Highest Energy Cosmic Rays
• Ultra-high energy cosmic rays from a finite number of point sources
• Astrophysical Neutrino Telescopes
• Cosmic Magnetic Fields and Their Influence on Ultra-High Energy Cosmic Ray Propagation
• Constraining the fraction of primary gamma rays at ultra-high energies from the muon data of the Yakutsk extensive-air-shower array
• Cosmogenic Neutrinos from Cosmic Ray Interactions with Extragalactic Infrared Photons
• TeV gamma-rays from photo-disintegration/de-excitation of cosmic-ray nuclei
• Centaurus A as the Source of ultra-high energy cosmic rays?
• The mass composition of cosmic rays above 10^17 eV
• The GZK cutoff behind a Magnetized Universe
• GZK Photons in the Minimal Ultra High Energy Cosmic Rays Model
• High Energy Neutrinos from Cosmic Ray Interactions in Clusters of Galaxies
• Propagation of ultra-high energy protons in regular extragalactic magnetic fields
• A New Estimate of the Extragalactic Gamma-Ray Background from EGRET Data
• Ultra High Energy Cosmic Rays Diffusion in an Expanding Universe
• TeV gamma-rays from photo-disintegration/de-excitation of nuclei in Westerlund 2

Cited by in corpus (16)

• Upper limit on the cosmic-ray photon flux above 10^19 eV using the surface detector of the Pierre Auger Observatory
• Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory
• Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays
• CRPropa 3.2 -- an advanced framework for high-energy particle propagation in extragalactic and galactic spaces
• Effects of uncertainties in simulations of extragalactic UHECR propagation, using CRPropa and SimProp
• The optical depth of the Universe to ultrahigh energy cosmic ray scattering in the magnetized large scale structure
• Inhomogeneous extragalactic magnetic fields and the second knee in the cosmic ray spectrum
• Magnetic diffusion effects on the Ultra-High Energy Cosmic Ray spectrum and composition
• Ultra-High Energy Cosmic Rays and the GeV-TeV Diffuse Gamma-Ray Flux
• Diffusion of cosmic rays at EeV energies in inhomogeneous extragalactic magnetic fields
• Ultra high energy photons as probes of Lorentz symmetry violations in stringy space-time foam models
• GZK Photons Above 10 EeV
• Quantum Gravity phenomenology: achievements and challenges
• Magnetic Suppression of Cosmic Rays' Flux in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• Search for photons at the Pierre Auger Observatory
• Ultra-high energy cosmic rays with UFA-15 source model in Bumblebee gravity theory