Implications of temporal features of UHECR fluxes on large scale anisotropies
Paper in proceeding, 2025
The origin of ultra-high-energy cosmic rays (UHECRs) is still an elusive question, mainly because the arrival directions do not point to a preferred source location. However, it has recently been observed that the amplitude of the dipole anisotropy detected by the Pierre Auger Observatory increases with the energy. This can be interpreted as an indication of the presence of a dominant source in the direction of the dipole, depending on the effects of the Galactic Magnetic Field (GMF). However, alternative interpretations need to be rigorously examined and ruled out before any final conclusions on the dipole anisotropy can be accepted. Using CRPropa 3.2 and current GMF models, we find that UHECRs entering the Milky Way can experience delays of hundreds of kiloyears in the range of rigidities observed by Auger. Based on the constructed spectrum of ages for observed UHECRs, we explore the possibility that temporal changes in the flux of extragalactic UHECRs can produce a dipole similar to that reported by Auger. We explore how discrete bursts can temporally modulate the UHECR flux and show that such injections can reproduce the observed features in the energy spectrum, as well as the dipole-like anisotropies in idealized scenarios.
Author
Janning Meinert
RAPP Center
Heidelberg University
Bergische Universität Wuppertal
Leonel Morejon
RAPP Center
Bergische Universität Wuppertal
Veronika Vašíčková
Bergische Universität Wuppertal
RAPP Center
L. Merten
Ruhr-Universität Bochum
RAPP Center
S. Aerdker
RAPP Center
Ruhr-Universität Bochum
Julia Tjus
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
RAPP Center
Ruhr-Universität Bochum
Karl Heinz Kampert
RAPP Center
Bergische Universität Wuppertal
Proceedings of Science
18248039 (eISSN)
Vol. 501 338
39th International Cosmic Ray Conference, ICRC 2025
Geneva, Switzerland,
Geneva, Switzerland,
Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.22323/1.501.0338