Ensemble fluctuations of the cosmic ray energy spectrum and the intergalactic magnetic field

Abstract

The origin of the most energetic cosmic ray particles is one of the most important open problems in astrophysics. Despite a big experimental effort done in the past years, the sources of these very energetic particles remain unidentified. Therefore, their distribution on the Universe and even their space density are still unknown. It has been shown that different spatial configurations of the sources lead to different energy spectra and composition profiles (in the case of sources injecting heavy nuclei) at Earth. These ensemble fluctuations are more important at the highest energies because only nearby sources, which are necessarily few, can contribute to the flux observed at Earth. This is due to the interaction of the cosmic rays with the low energy photons of the radiation field, present in the intergalactic medium, during propagation. It is believed that the intergalactic medium is permeated by a turbulent magnetic field. Although at present it is still unknown, there are several constraints for its intensity and coherence length obtained from different observational techniques. Charged cosmic rays are affected by the intergalactic magnetic field because of the bending of their trajectories during propagation through the intergalactic medium. In this work, the influence of the intergalactic magnetic field on the ensemble fluctuations is studied. Sources injecting only protons and only iron nuclei are considered. The ensemble fluctuations are studied for different values of the density of sources compatible with the constraints recently obtained from cosmic ray data. Also, the possible detection of the ensemble fluctuations in the context of the future JEM-EUSO mission is discussed.

arXiv commentAccepted for publication in Physical Review D

References in corpus (26)

• Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
• The Astrophysics of Ultrahigh Energy Cosmic Rays
• Monte-Carlo simulations of photohadronic processes in astrophysics
• Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment
• Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
• Kneelike structure in the spectrum of the heavy component of cosmic rays observed with KASCADE-Grande
• Study of Ultra-High Energy Cosmic Ray Composition Using Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode
• The Jem-Euso Mission
• An evaluation of the exposure in nadir observation of the JEM-EUSO mission
• CRPropa 2.0 -- a Public Framework for Propagating High Energy Nuclei, Secondary Gamma Rays and Neutrinos
• Lensing of ultra-high energy cosmic rays in turbulent magnetic fields
• Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition
• Anisotropies of ultra-high energy cosmic rays diffusing from extragalactic sources
• The need for a local source of UHE CR nuclei
• A Magnetized Local Supercluster and the Origin of the Highest Energy Cosmic Rays
• Search for Extended γ-ray Emission around AGN with H.E.S.S. and Fermi-LAT
• Highlights from the Pierre Auger Observatory
• Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory
• The Pierre Auger Observatory I: The Cosmic Ray Energy Spectrum and Related Measurements
• Cosmic Rays: Recent Progress and some Current Questions
• On numerical turbulence generation for test-particle simulations
• Anisotropy expectations for ultra-high-energy cosmic rays with future high statistics experiments
• Cosmic Magnetic Fields: Observations and Prospects
• Pierre Auger Observatory and Telescope Array: Joint Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)
• Ensemble Fluctuations of the Flux and Nuclear Composition of Ultra-High Energy Cosmic Ray Nuclei
• Sensitivity of JEM-EUSO to Ensemble Fluctuations in the Ultra-High Energy Cosmic Ray Flux