Diffusion coefficient and acceleration spectrum from direct measurements of charged cosmic ray nuclei

Castellina, A.; Donato, Fiorenza

doi:10.1016/j.astropartphys.2005.06.006

Cited by 35 publications

(23 citation statements)

References 48 publications

(48 reference statements)

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“…This situation is likely to be remedied in the future. Better B/C data should help for improving the determinations of the K/L ratio and of the spectral index δ as discussed in Castellina & Donato (2005). Accurate measurements of the 10 Be/ 9 Be ratio would then help lift the degeneracy between L and K. Once again, there is matter for some hope with forthcoming experiments like AMS02 (Incagli 2010) or CREAM (Ahn et al 2010).…”

Section: Discussionmentioning

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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Section: Discussionmentioning

confidence: 99%

The GeV-TeV Galactic gamma-ray diffuse emission

Delahaye

Fiaßon

Pohl

et al. 2011

A&A

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“…Data in the same energy range from PAMELA would be helpful in that respect. Moreover, high energy data from subsequent CREAM flights or from the TRACER experiments will be a crucial test of the diffusion slope: at TeV energies, diffusion alone is expected to shape the observed spectra, so that the ambiguity with the effect of convection or reacceleration is lifted (Castellina & Donato 2005).…”

Section: Sensitivity To the Choice Of The B/c Datasetmentioning

confidence: 99%

A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays

Putze¹,

Derome²,

Maurin

et al. 2009

A&A

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Context. Propagation of charged cosmic-rays in the Galaxy depends on the transport parameters, whose number can be large depending on the propagation model under scrutiny. A standard approach for determining these parameters is a manual scan, leading to an inefficient and incomplete coverage of the parameter space. Aims. In analyzing the data from forthcoming experiments, a more sophisticated strategy is required. An automated statistical tool is used, which enables a full coverage of the parameter space and provides a sound determination of the transport and source parameters. The uncertainties in these parameters are also derived. Methods. We implement a Markov Chain Monte Carlo (MCMC), which is well suited to multi-parameter determination. Its specificities (burn-in length, acceptance, and correlation length) are discussed in the context of cosmic-ray physics. Its capabilities and performances are explored in the phenomenologically well-understood Leaky-Box Model. Results. From a technical point of view, a trial function based on binary-space partitioning is found to be extremely efficient, allowing a simultaneous determination of up to nine parameters, including transport and source parameters, such as slope and abundances. Our best-fit model includes both a low energy cut-off and reacceleration, whose values are consistent with those found in diffusion models. A Kolmogorov spectrum for the diffusion slope (δ = 1/3) is excluded. The marginalised probability-density function for δ and α (the slope of the source spectra) are δ ≈ 0.55−0.60 and α ≈ 2.14−2.17, depending on the dataset used and the number of free parameters in the fit. All source-spectrum parameters (slope and abundances) are positively correlated among themselves and with the reacceleration strength, but are negatively correlated with the other propagation parameters. Conclusions. The MCMC is a practical and powerful tool for cosmic-ray physic analyses. It can be used to confirm hypotheses concerning source spectra (e.g., whether α i α j ) and/or determine whether different datasets are compatible. A forthcoming study will extend our analysis to more physical diffusion models.

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“…Furthermore, other uncertainties related to the physics of solar modulation and to poorly known nuclear cross sections are reduced by considering only data at energies larger than several GeV/n. Hence, the study of high energy CR spectra allows in principle to constrain the plain diffusion properties of CR in the Galaxy, in particular the strength D 0 of the diffusion coefficient at a reference rigidity and its energy slope δ, and offers a lever arm to better understand low energy effects (see [10] for an interesting discussion about this issue). This possibility has been precluded for long time by the scarcity of observational data.…”

Section: Introductionmentioning

confidence: 99%

Unified interpretation of cosmic ray nuclei and antiproton recent measurements

Bernardo

Evoli

Gaggero

et al. 2010

Astroparticle Physics

122

144

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We use our numerical code, DRAGON, to study the implications of recent data on our knowledge of the propagation properties of cosmic ray nuclei in the Galaxy. We show that B/C (as well as N/O and C/O) data, including those recently taken by CREAM, andp/p data, especially including recent PAMELA results, can consistently be fitted within a unique diffusion-reacceleration model. The requirement that light nuclei andp data are consistently reproduced within experimental uncertainties places significant limits on the main propagation parameters. In particular, we find the allowed range of the diffusion coefficient spectral index to be 0.3 < δ < 0.6 at 95% confidence level and that Kraichnan type diffusion is favored with respect to Kolmogorov. While some amount of reacceleration is required, only a limited range of the Alfvèn velocity value (10 < ∼ v A < ∼ 20 km s −1 ) is allowed by a combined analysis of nuclear and antiproton data, which we perform here for the first time. If antiproton data are not used to constrain the propagation parameters, a larger set of models is allowed. In this case, we determine which combinations of the relevant parameters maximize and minimize the antiproton flux under the condition of still fitting light nuclei data at 95% C.L. These models may then be used to constrain a possible extra antiproton component arising from astrophysical or exotic sources (e.g. dark matter annihilation or decay).

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Diffusion coefficient and acceleration spectrum from direct measurements of charged cosmic ray nuclei

Cited by 35 publications

References 48 publications

The GeV-TeV Galactic gamma-ray diffuse emission

The GeV-TeV Galactic gamma-ray diffuse emission

A Markov Chain Monte Carlo technique to sample transport and source parameters of Galactic cosmic rays

Unified interpretation of cosmic ray nuclei and antiproton recent measurements

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