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Implications of Strong Intergalactic Magnetic Fields for Ultra-High-Energy Cosmic-Ray Astronomy
High Energy Astrophysical Phenomena · Submitted 19 Apr 2017
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux.
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The abstract, sentence by sentence
We study the propagation of ultra-high-energy cosmic rays in the magnetised cosmic web. We focus on the particular case of highly magnetised voids ($B \sim \text{nG}$), using the upper bounds from the Planck satellite. The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to $\simeq 80\%$ and $\simeq 5\%$, respectivelly. In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than $\sim\;$50 Mpc are less than $15^\circ$ in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study the propagation of ultra-high-energy cosmic rays in the magnetised cosmic web. | contribution 0.99 | 0.90 | 0.03 | asserted 0.79 |
| s1 | We focus on the particular case of highly magnetised voids ($B \sim \text{nG}$), using the upper bounds from the Planck satellite. | method 0.52 | 0.63 | 0.03 | asserted 0.85 |
| s2 | The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. | method 1.00 | 0.84 | 0.02 | asserted 0.99 |
| s3 | We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to $\simeq 80\%$ and $\simeq 5\%$, respectivelly. | result 1.00 | 0.91 | 0.20 | asserted 0.97 |
| s4 | In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than $\sim\;$50 Mpc are less than $15^\circ$ in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. | result 1.00 | 0.91 | 0.24 | asserted 0.97 |
| s5 | Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux. | interpretation 1.00 | 0.62 | 0.81 | speculative 0.57 |
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The paper
Original abstract
We study the propagation of ultra-high-energy cosmic rays in the magnetised cosmic web. We focus on the particular case of highly magnetised voids ($B \sim \text{nG}$), using the upper bounds from the Planck satellite. The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to $\simeq 80\%$ and $\simeq 5\%$, respectivelly. In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than $\sim\;$50 Mpc are less than $15^\circ$ in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux.
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References
How the literature uses it
21 arXiv papers cite this in 36 sentences
Papers citing it · 26 sentences without a confident label
Compares with it 1 paper
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In all the obtained models the minimum magnetization level is much smaller than e.g. in Refs. [ref] .
Extragalactic Sources and Propagation of UHECRs · EGMFs from simulations with ENZO · 0.99
Cites it as support 1 paper
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A requirement for this scenario not to violate isotropy constraints is that extragalactic magnetic fields are strong enough to largely isotropize UHECR arriving from Cygnus A, which we found possible for extreme EGMF scenarios [ref] .
Ultra-High-Energy Cosmic Rays from Radio Galaxies · Conclusions and Outlook · 0.99
Cites it as background 7 papers
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Various work has been done to estimate the effect of realistic EGMF structure on UHECR propagation [ref] .
Ultra-High-Energy Cosmic Rays from Radio Galaxies · Introduction · 0.98
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Nowadays, there are several structured extra-galactic magnetic field models available such as [ref] .
Anisotropies of Ultra-high Energy Cosmic Rays Dominated by a Single Source in the Presence of Deflections · Comparison with structured magnetic fields · 0.88
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A number of works [ref] has discussed the effects of extragalactic magnetic fields on the propagation of UHECRs, though with conflicting conclusions due to the different assumptions and owing to our lack of knowledge about magnetic field distributions in the Universe.
On the Measurement of the Helicity of Intergalactic Magnetic Fields Using Ultra-High-Energy Cosmic Rays · Introduction · 0.98
What it cites · 44 sentences without a confident label
Uses the method or tool of 8 papers
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The propagation was done using the CRPropa 3 code [ref] .
CRPropa 3 - a Public Astrophysical Simulation Framework for Propagating Extraterrestrial Ultra-High Energy Particles · Simulation setup · 1.00
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MHD simulations using RAMSES [ref] were performed.
Cosmological Hydrodynamics with Adaptive Mesh Refinement: a new high resolution code called RAMSES · The simulated cosmic web · 1.00
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The model by Das et al. [ref] , on the other hand, uses the method presented in Ref. [ref] to infer the magnetic field energy, based on the vorticity and kinetic energy of the turbulent flow in the simulations.
Turbulence and Magnetic Fields in the Large Scale Structure of the Universe · The simulated cosmic web · 0.88
Uses data or values from 13 papers
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The most recent results by the Planck Collaboration sets the upper bound to $4.4 nG$ for zero helicity, and $5.6 nG$ for maximal helicity, at comoving scales of 1 Mpc, at 95% confidence level [ref] .
Planck 2015 results. XIX. Constraints on primordial magnetic fields · The simulated cosmic web · 0.99
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Constraints based on Faraday rotation measurements using the NRAO VLA Sky Survey are $B ≲1 nG$ for fields whose coherence lengths are of the order of the Jeans' length [ref] .
New limits on extragalactic magnetic fields from rotation measures · The simulated cosmic web · 0.87
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In fact, Auger has observed an excess of UHECRs with energies $E > 58 EeV$ within a window of 15$^∘$ around Cen A [ref] .
Searches for Anisotropies in the Arrival Directions of the Highest Energy Cosmic Rays Detected by the Pierre Auger Observatory · Auger and TA hotspots · 0.84
Compares with 3 papers
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Model I ($B ∝ρ_g^2/3$) by Kotera & Lemoine [ref] and model `agn' by Hackstein et al. [ref] , for instance, have an overall similar slope to our models (runs F, L, S, and O).
Inhomogeneous extragalactic magnetic fields and the second knee in the cosmic ray spectrum · The simulated cosmic web · 1.00
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Model I ($B ∝ρ_g^2/3$) by Kotera & Lemoine [ref] and model `agn' by Hackstein et al. [ref] , for instance, have an overall similar slope to our models (runs F, L, S, and O).
Propagation of Ultra High Energy Cosmic Rays in Extragalactic Magnetic Fields: A view from cosmological simulations · The simulated cosmic web · 1.00
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For reference, we present the spectra together with data measured by the Pierre Auger Observatory [ref] and the Telescope Array [ref] .
The Pierre Auger Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015) · Spectrum and composition · 0.80
Cites as support 2 papers
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Results by the Pierre Auger Observatory [ref] support the extragalactic origin of cosmic rays at the highest energies, although the presence of a galactic component at energies of a few EeV is not excluded and has been advocated by several authors (see e.g. refs.
Constraints on the origin of cosmic rays above $10^{18}$ eV from large scale anisotropy searches in data of the Pierre Auger Observatory · Introduction · 0.96
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Energy losses caused by the adiabatic expansion of the universe as well as the redshift evolution of the CMB and EBL densities were not taken into account in this approach as these effects are subdominant at $E ≳10 EeV$, as argued in Ref. [ref] .
Propagation of UHECRs in the Universe · Simulation setup · 0.98
Cites as background 14 papers
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Seminal works by Sigl et al. [ref] and Dolag et al. [ref] have discussed the deflection of UHECRs in EGMFs and the prospects for identifying their sources making use of MHD simulations of the magnetised cosmic web.
Constrained Simulations of the Magnetic Field in the Local Universe and the Propagation of UHECRs · Introduction · 0.97
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Seminal works by Sigl et al. [ref] and Dolag et al. [ref] have discussed the deflection of UHECRs in EGMFs and the prospects for identifying their sources making use of MHD simulations of the magnetised cosmic web.
Mapping deflections of extragalactic Ultra-High Energy Cosmic Rays in magnetohydrodynamic simulations of the Local Universe · Introduction · 0.97
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Seminal works by Sigl et al. [ref] and Dolag et al. [ref] have discussed the deflection of UHECRs in EGMFs and the prospects for identifying their sources making use of MHD simulations of the magnetised cosmic web.
Cosmic Magnetic Fields and Their Influence on Ultra-High Energy Cosmic Ray Propagation · Introduction · 0.97
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