Energy spectra and composition of primary cosmic rays

Mueller, D.; Swordy, S. P.; Meyer, P.; L’Heureux, J.; Grunsfeld, J. M.

doi:10.1086/170125

Cited by 188 publications

(100 citation statements)

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“…3, we have analysed the fluxes of primary cosmic rays in diffusion models with particular attention to p and He. The most recent data on p and He are well reproduced by a purely diffusive model, described by power-law source (Ahn et al 2008(Ahn et al , 2010a, CRN (Swordy et al 1990;Mueller et al 1991), HEAO-3 (Engelmann et al 1990), TRACER (Ave et al 2008(Ave et al , 2009, and low-energy ACE data (George et al 2009). spectrum, isotropic diffusion coefficient, spallative destructions and electromagnetic energy losses. This conclusion holds for single data sets but it is not reproduced in a combined data analysis (except for AMS01 and BESS98 proton data), due to the mean level of consistency among the different data collections.…”

Section: Discussionmentioning

confidence: 83%

p, He, and C to Fe cosmic-ray primary fluxes in diffusion models

Putze

Maurin

Donato

2011

A&A

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Context. The source spectrum of cosmic rays is not well determined by diffusive shock acceleration models. The propagated fluxes of proton, helium, and heavier primary cosmic-ray species (up to Fe) are a means to indirectly access it. But how robust are the constraints, and how degenerate are the source and transport parameters? Aims. We check the compatibility of the primary fluxes with the transport parameters derived from the B/C analysis, but also ask whether they add further constraints. We study whether the spectral shapes of these fluxes and their ratios are mostly driven by source or propagation effects. We then derive the source parameters (slope, abundance, and low-energy shape). Methods. Simple analytical formulae are used to address the issue of degeneracies between source/transport parameters, and to understand the shape of the p/He and C/O to Fe/O data. The full analysis relies on the USINE propagation package, the MINUIT minimisation routines (χ 2 analysis) and a Markov Chain Monte Carlo (MCMC) technique. Results. Proton data are well described in the simplest model defined by a power-law source spectrum and plain diffusion. They can also be accommodated by models with, e.g., convection and/or reacceleration. There is no need for breaks in the source spectral indices below ∼1 TeV/n. Fits to the primary fluxes alone do not provide physical constraints on the transport parameters. If we leave the source spectrum free, parametrised by the form dQ/dE = qβ η S R −α , and fix the diffusion coefficient K(R) = K 0 β η T R δ so as to reproduce the B/C ratio, the MCMC analysis constrains the source spectral index α to be in the range 2.2−2.5 for all primary species up to Fe, regardless of the value of the diffusion slope δ. The values of the parameter η S describing the low-energy shape of the source spectrum are degenerate with the parameter η T describing the low-energy shape of the diffusion coefficient: we find η S − η T ≈ 0 for p and He data, but η S − η T ≈ 1 for C to Fe primary species. This is consistent with the toy-model calculation in which the shape of the p/He and C/O to Fe/O data is reproduced if η S − η T ≈ 0−1 (no need for different slopes α). When plotted as a function of the kinetic energy per nucleon, the low-energy p/He ratio is determined mostly by the modulation effect, whereas primary/O ratios are mostly determined by their destruction rate. Conclusions. Models based on fitting B/C are compatible with primary fluxes. The different spectral indices for the propagated primary fluxes up to a few TeV/n can be naturally ascribed to transport effects only, implying universality of elemental source spectra.

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Section: Discussionmentioning

confidence: 83%

p, He, and C to Fe cosmic-ray primary fluxes in diffusion models

Putze

Maurin

Donato

2011

A&A

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“…5. The solid line represents our results, and the data are taken from CREAM (Ahn et al 2009), ATIC (Panov et al 2007), CRN (Müller et al 1991;Swordy et al 1990), HEAO (Engelmann et al 1990), and TRACER (Obermeier et al 2011). The carbon and oxygen source parameters used are (q C = 2.24, f C = 0.024%), and (q O = 2.26, f O = 0.025%) respectively, where the f 's are given in units of 10 51 ergs.…”

Section: Comparison With the Datamentioning

confidence: 99%

“…4. Data: CREAM (Ahn et al 2009), ATIC (Panov et al 2007), CRN (Müller et al 1991;Swordy et al 1990), HEAO (Engelmann et al 1990), and TRACER (Obermeier et al 2011). the normal component. The spectral roll-off above ∼10 5 GeV/n is due to the assumed exponential cutoff of the source spectrum at p c which we keep fixed at 10 6 GeV/c for protons.…”

Section: Comparison With the Datamentioning

confidence: 99%

GeV-TeV cosmic-ray spectral anomaly as due to reacceleration by weak shocks in the Galaxy

Thoudam

Hörandel

2014

A&A

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Recent cosmic-ray measurements have found an anomaly in the cosmic-ray energy spectrum at GeV-TeV energies. Although the origin of the anomaly is not clearly understood, suggested explanations include the effect of cosmic-ray source spectrum, propagation effects, and the effect of nearby sources. In this paper, we propose that the spectral anomaly might be an effect of reacceleration of cosmic rays by weak shocks in the Galaxy. After acceleration by strong supernova remnant shock waves, cosmic rays undergo diffusive propagation through the Galaxy. During the propagation, cosmic rays may again encounter expanding supernova remnant shock waves, and get re-accelerated. As the probability of encountering old supernova remnants is expected to be larger than the younger remnants because of their bigger sizes, reacceleration is expected to be produced mainly by weaker shocks. Since weaker shocks generate a softer particle spectrum, the resulting re-accelerated component will have a spectrum steeper than the initial cosmic-ray source spectrum produced by strong shocks. For a reasonable set of model parameters, it is shown that the re-accelerated component can dominate the GeV energy region while the non-reaccelerated component dominates at higher energies, thereby explaining the observed GeV-TeV spectral anomaly.

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“…Many works have been dedicated to using the secondary-toprimary ratios and the unstable-to-stable isotope ratios to constrain the CR propagation parameters (see e.g., [6,9,[12][13][14][15][16][17][18][19]). However, due to the large number of the model parameters and the degeneracy between different parameters, the investigation of the parameter space is incomplete and the conclusion might be biased.…”

Section: Introductionmentioning

confidence: 99%

Propagation of cosmic rays in the AMS-02 era

et al. 2017

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In this work we use the newly reported Boron-to-Carbon ratio (B/C) from AMS-02 and the time-dependent proton fluxes from PAMELA and AMS-02 to constrain the source and propagation parameters of cosmic rays in the Milky Way. A linear correlation of the solar modulation parameter with solar activities is assumed to account for the time-varying cosmic ray fluxes. A comprehensive set of propagation models, with/without reacceleration or convection, have been discussed and compared. We find that only the models with reacceleration can selfconsistently fit both the proton and B/C data. The rigidity dependence slope of the diffusion coefficient, δ, is found to be about 0.38 − 0.50 for the diffusion-reacceleration models. The plain diffusion and diffusionconvection models fit the data poorly. We compare different model predictions of the positron and antiproton fluxes with the data. We find that the diffusion-reacceleration models over-produce low energy positrons, while non-reacceleration models give better fit to the data. As for antiprotons, reacceleration models tend to underpredict low energy antiproton fluxes, unless a phenomenological modification of the velocity-dependence of the diffusion coefficient is applied. Our results suggest that there could be important differences of the propagation for nuclei and leptons, in either the Milky Way or the solar heliosphere.PACS numbers: 95.35.+d,96.50.S-

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Energy spectra and composition of primary cosmic rays

Cited by 188 publications

References 0 publications

p, He, and C to Fe cosmic-ray primary fluxes in diffusion models

p, He, and C to Fe cosmic-ray primary fluxes in diffusion models

GeV-TeV cosmic-ray spectral anomaly as due to reacceleration by weak shocks in the Galaxy

Propagation of cosmic rays in the AMS-02 era

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