Evidence for correlated changes in the spectrum and composition of cosmic rays at extremely high energies

Bird, D. J.; Corbató, S. C.; Dai, H. Y.; Dawson, B. R.; Elbert, J. W.; Gaisser, T. K.; Green, K. D.; Huang, M. A.; Kieda, D. B.; Ko, S.; Larsen, C. G.; Loh, E. C.; Luo, Marie S. C.; Salamon, M. H.; Smith, D. L.; Sokolsky, P.; Sommers, P.; Stanev, T.; Tang, J. K. K.; Thomas, S. B.; Tilav, S.

doi:10.1103/physrevlett.71.3401

Cited by 455 publications

(250 citation statements)

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“…The chemical composition of ultrahigh energy cosmic-rays indeed remains an open question. While experiments such as the Fly's Eye and HiRes have suggested a transition from heavy to light above ∼10 18.5 eV (Bird et al 1993;Abbasi et al 2005Abbasi et al , 2010, the most recent measurements made with the Pierre Auger Observatory point instead towards a heavy composition above 10 19 eV (Unger et al 2007;Abraham et al 2009Abraham et al , 2010. As the energy losses and magnetic deflection of high energy nuclei differ from those of a proton of a same energy, one should naturally expect different gamma-ray signatures.…”

Section: Introductionmentioning

confidence: 99%

Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays

Kotera

Allard

Lemoine

2011

A&A

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The injection of ultrahigh energy cosmic-rays in the intergalactic medium leads to the production of a GeV-TeV gamma-ray halo centered on the source location, through the production of a high electromagnetic component in the interactions of the primary particles with the radiation backgrounds. This paper examines the prospects for the detectability of such gamma-ray halos. We explore a broad range of astrophysical parameters, including the inhomogeneous distribution of magnetic fields in the large-scale structure, as well as various possible chemical compositions and injection spectra; and we consider the case of a source located outside clusters of galaxies. We demonstrate that the gamma-ray flux associated to synchrotron radiation of ultrahigh energy secondary pairs does not depend strongly on these parameters, and conclude that its magnitude ultimately depends on the energy injected into the primary cosmic-rays. We find that the gamma-ray halo produced by equal luminosity sources (with cosmic ray luminosity and source density chosen to reproduce the measured cosmic-ray spectrum) is far fainter than current or planned instrument sensitivities. Only rare and powerful steady sources, located at distances larger than several hundreds of Mpc and contributing to a fraction 10% of the flux at 10 19 eV might be detectable. We also discuss the gamma-ray halos that are produced by inverse Compton/pair production cascades seeded by ultrahigh energy cosmic-rays. This depends strongly on the configuration of the extragalactic magnetic fields; it is dominated by the synchrotron signal on a degree scale if the filling factor of magnetic fields with B 10 −14 G is smaller than a few percent. Finally, we briefly discuss the case of nearby potential sources such as Centaurus A.

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Section: Introductionmentioning

confidence: 99%

Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays

Kotera

Allard

Lemoine

2011

A&A

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“…The integral flux of cosmic rays with primary energy above 10 19 eV is about one particle per square kilometer per year, probably dropping by a factor of a hundred at energies above 10 20 eV. Although there is evidence that the highest energy particles are predominantly protons (Bird 1993), the number of photons at energies above 10 19 eV may be significant for two reasons. The EHE cosmic ray protons, distributed uniformly in the universe, produce many photons in collisions with the microwave background radiation photons (Wdowczyk 1990;Halzen 1990).…”

Section: Introductionmentioning

confidence: 87%

Development of electromagnetic cascading in the Sun's magnetic field

Mahrous

Inoue

2002

A&A

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Abstract. The study of particle cascading initiated by Extremely High Energy (EHE) photons in the Sun's magnetic field offers us an opportunity to study some processes of astrophysical importance in space. This opportunity has been particularly useful in investigating the photon content in the EHE cosmic ray spectrum. The processes of magnetic pair creation and photon splitting are the basic mechanisms taken into account in our Monte Carlo simulation code. Such processes have been simulated for primary photons in the magnetic field near the Sun to study the characteristics of the cascading of these extraordinary showers. Upon simulation, such cascading particles produced by primary photons with an energy ≥10 19 eV could be detected on the Earth's surface within a solid angle of 6.12 × 10 −4 sr from the Sun's position. The characteristics of cascading initiated by photons in such a strong magnetic field near the Sun are discussed.

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“…2). The picture is not as clear as it first appeared in the original stereo Fly's Eye result [6]. For example, the coincident measurements of the prototype HiRes Fly's Eye with the MIA ground array [7], as shown by the gray, filled circles in Fig.…”

Section: Extragalactic Component Of Cosmic Raysmentioning

confidence: 94%

“…Note that this result assumes the extragalactic spectrum extends down to ∼ 1 GeV. Replacing [18] Haverah Park [19] Yakutsk [20] Fly's Eye (mono) [21] Fly's Eye (stereo) [6] FIGURE 2. The high energy cosmic rays spectrum.…”

Section: A Normalization At High Energymentioning

confidence: 99%

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High energy neutrino astronomy—the cosmic-ray connection

Gaisser¹

2001

AIP Conference Proceedings

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Abstract. Several of the models for origin of the highest energy cosmic rays also predict significant neutrino fluxes. A common factor of the models is that they must provide sufficient power to supply the observed energy in the extragalactic component of the cosmic radiation. The assumption that a comparable amount of energy goes into high-energy neutrinos allows a model-independent estimate of the neutrino signal that may be expected. I INTRODUCTIONAn important argument in favor of supernova explosions as the power source for galactic cosmic rays is the fact that kinetic energy of the ejecta supplies the right amount of power. The energy content of the cosmic radiation iswhere φ(E) = dN/dE is the measured local flux of cosmic rays corrected for the effect of solar modulation. In the source region the average energy density in cosmic rays is related to the average production rate per unit volume, q(E), bywhere τ esc is the characteristic residence time of cosmic rays in the source region (for example the disk of the galaxy). The characteristic time, τ esc (E), decreases with energy [1] so that the observed spectrum is somewhat steeper than the source spectrum.Given an estimate of τ esc and the rate of supernova explosions, it is possible to estimate the fraction of energy of supernova explosions needed to maintain the galactic cosmic rays in steady state, assuming that supernovae provide the power, q(E). Assuming a rate of three supernovae per century with a kinetic energy of 10 51 1) Research supported in part by NASA grant NAG5-7009

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Evidence for correlated changes in the spectrum and composition of cosmic rays at extremely high energies

Cited by 455 publications

References 13 publications

Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays

Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays

Development of electromagnetic cascading in the Sun's magnetic field

High energy neutrino astronomy—the cosmic-ray connection

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