Discrepant Hardening Observed in Cosmic-Ray Elemental Spectra

Ahn, H. S.; Allison, P.; Bagliesi, Maria Grazia; Beatty, J. J.; Bigongiari, G.; Childers, J. T.; Conklin, N. B.; Coutu, S.; DuVernois, M. A.; Ganel, O.; Han, Ji Hye; Jeon, J. A.; Kim, K. C.; Lee, Moo Hyun; Lutz, L.; Maestro, P.; Малинин, А.; Marrocchesi, P. S.; Minnick, S.; Mognet, S. I.; Nam, J. W.; Nam, S. W.; Nutter, S.; Park, I. H.; Park, N. H.; Seo, E. S.; Sina, R.; Wu, J.; Yang, J.; Yoon, Y. S.; Zei, R.; Zinn, S. Y.

doi:10.1088/2041-8205/714/1/l89

Cited by 384 publications

(360 citation statements)

References 31 publications

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“…As shown by Blasi et al (2012) and later by Aloisio & Blasi (2013), the transition between the two reflects in a change of slope in the spectra of primary elements, most notably protons and helium nuclei. Evidence in favor of this kind of break emerged first in nuclear spectra (Ahn 2010). Then, hints for something similar in proton and helium spectra were suggested by the need to reconcile high-energy data measured by CREAM (Yoon et al 2011) with low-energy data, and, more recently, PAMELA (Adriani 2011) reported for the first time the detection of the transition in proton and helium nuclei.…”

Section: Discussionmentioning

confidence: 97%

Nonlinear cosmic ray Galactic transport in the light of AMS-02 and Voyager data

Aloisio

Blasi

Serpico

2015

A&A

111

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Context. Features in the spectra of primary cosmic rays (CRs) provide invaluable information on the propagation of these particles in the Galaxy. In the rigidity region around a few hundred GV, these features have been measured in the proton and helium spectra by the PAMELA experiment and later confirmed with a higher significance by AMS-02. We investigate the implications of these data sets for the scenario in which CRs propagate under the action of self-generated waves. Aims. We show that the recent data on the spectrum of protons and helium nuclei as collected with AMS-02 and Voyager are in very good agreement with the predictions of a model in which the transport of Galactic CRs is regulated by self-generated waves. We also study the implications of the scenario for the boron-to-carbon ratio: although a good overall agreement is found, at high energy we find marginal support for a (quasi) energy independent contribution from the grammage, which we argue may come from the sources themselves. Methods. The transport equation for both primary and secondary nuclei is solved together with an equation for the evolution of the self-generated waves and a background of pre-existing waves. The solution for this system of nonlinear equations is found with an iterative method elaborated by the same authors in a previous work on this topic. Results. A break in the spectra of all nuclei is found at a rigidity of a few hundred GV, as a result of a transition from self-generated waves to pre-existing waves with a Kolmogorov power spectrum. Neither the slope of the diffusion coefficient, nor its normalization are free parameters. Moreover, at rigidities below a few GV, CRs are predicted to be advected with the self-generated waves at the local Alfvén speed. This effect, predicted in our previous work, provides an excellent fit to the Voyager data on the proton and helium spectra at low energies, providing additional support to the model.

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Section: Discussionmentioning

confidence: 97%

Nonlinear cosmic ray Galactic transport in the light of AMS-02 and Voyager data

Aloisio

Blasi

Serpico

2015

A&A

111

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“…The photon production cross sections of these processes are likely to be better parameterized in the future leading to improvement in our understanding of the mechanisms at work. The CR proton and helium fluxes at the Earth will also be soon measured with much better accuracy by experiments like AMS02 (Incagli 2010) or CREAM (Ahn et al 2010). …”

Section: Discussionmentioning

confidence: 99%

“…The balloon experiments ATIC2 (Panov et al 2009) and CREAM (Ahn et al 2010) have recently reported a significant hardening of the proton and helium spectra above 200 GeV/n. Although both experiments agree on the helium spectrum, ATIC2 finds a larger proton excess than CREAM.…”

Section: Cosmic Ray Proton and Helium Fluxes At The Earthmentioning

confidence: 99%

The GeV-TeV Galactic gamma-ray diffuse emission

Delahaye

Fiaßon

Pohl

et al. 2011

A&A

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Context. The Galactic γ-ray diffuse emission is currently observed in the GeV-TeV energy range with unprecedented accuracy by the Fermi satellite. Understanding this component is crucial because it provides a background to many different signals, such as extragalactic sources or annihilating dark matter. It is timely to reinvestigate how it is calculated and to assess the various uncertainties that are likely to affect the accuracy of the predictions. Aims. The Galactic γ-ray diffuse emission is mostly produced above a few GeV by the interactions of cosmic ray primaries impinging on the interstellar material. The theoretical error on that component is derived by exploring various potential sources of uncertainty. Particular attention is paid to cosmic ray propagation. Nuclear cross sections, the proton and helium fluxes at the Earth's position, the Galactic radial profile of supernova remnants, and the hydrogen distribution can also severely affect the signal. Methods. The propagation of cosmic ray species throughout the Galaxy is described in the framework of a semi-analytic two-zone diffusion/convection model. The γ-ray flux is reliably and quickly determined. This allows conversion of the constraints set by the boron-to-carbon data into a theoretical uncertainty on the diffuse emission. New deconvolutions of the HI and CO sky maps are also used to get the hydrogen distribution within the Galaxy. Results. The thickness of the cosmic ray diffusive halo is found to have a significant effect on the Galactic γ-ray diffuse emission, while the interplay between diffusion and convection has little influence on the signal. The uncertainties related to nuclear cross sections and to the primary cosmic ray fluxes at the Earth are significant. The radial distribution of supernova remnants along the Galactic plane turns out to be a key ingredient. As expected, the predictions are extremely sensitive to the spatial distribution of hydrogen within the Milky Way. Conclusions. Most of the sources of uncertainty are likely to be reduced in the near future. The stress should be put (i) on better determination of the thickness of the cosmic ray diffusive halo; and (ii) on refined observations of the radial profile of supernova remnants.

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“…The final ingredient is the average supernova explosion rate ν. We used these parameters to compute the proton and helium fluxesΦ ext + Φ cat over an energy range extending from 50 GeV/nuc to 100 TeV/nuc, in order to compare them with the PAMELA (Adriani et al 2011) and CREAM (Ahn et al 2010) data. At high energy, solar modulation has little effect on the CR flux, and it has not been taken into account in this study.…”

Section: Scan Of the Parameter Spacementioning

confidence: 99%

“…As already explained, the thinner the magnetic halo, the smaller the number N of sources that contribute to the total signal and the greater the injection rate q of individual sources. Table 2), giving the best fit to the PAMELA (Adriani et al 2011) and CREAM (Ahn et al 2010) data: supernovae explosion rate ν = 0.8 century −1 . Solid lines show the total flux, short-dashed lines show the flux due to the sources of the catalog, and the long-dashed curve the flux due to the rest of the sources.…”

Section: Value Of Lmentioning

confidence: 99%

TeV cosmic-ray proton and helium spectra in the myriad model

Bernard

Delahaye

Keum

et al. 2013

A&A

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Context. Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundred GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. Aims. We propose here to explain this anomaly by the presence of local sources (myriad model). Methods. Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. As an improvement over a similar analysis, we consistently derive these fluxes by taking both local and remote sources for which a unique injection rate is assumed into account. Results. We find cosmic ray propagation parameters compatible with B/C measurements for which the proton and helium spectra agree remarkably with the PAMELA and CREAM measurements over four decades in energy.

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Discrepant Hardening Observed in Cosmic-Ray Elemental Spectra

Cited by 384 publications

References 31 publications

Nonlinear cosmic ray Galactic transport in the light of AMS-02 and Voyager data

Nonlinear cosmic ray Galactic transport in the light of AMS-02 and Voyager data

The GeV-TeV Galactic gamma-ray diffuse emission

TeV cosmic-ray proton and helium spectra in the myriad model

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