Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition

In this paper we investigate the effect of stochasticity in the spatial and temporal distribution of supernova remnants on the spectrum and chemical composition of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) experienced by c...

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Published inJournal of cosmology and astroparticle physics Vol. 2012; no. 1; pp. 010 - 28
Main Authors Blasi, Pasquale, Amato, Elena
Format Journal Article
LanguageEnglish
Published United States IOP Publishing 01.01.2012
Subjects
ANISOTROPY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
COSMIC RADIATION
COSMIC RAY PROPAGATION
Cosmic rays
COSMOLOGY
Earth
FLUCTUATIONS
HELIUM
Mathematical analysis
MILKY WAY
PROTONS
PULSARS
STOCHASTIC PROCESSES
Stochasticity
SUPERNOVA REMNANTS
SUPERNOVAE
Temporal distribution
TEV RANGE
TIME DEPENDENCE
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Summary:In this paper we investigate the effect of stochasticity in the spatial and temporal distribution of supernova remnants on the spectrum and chemical composition of cosmic rays observed at Earth. The calculations are carried out for different choices of the diffusion coefficient D(E) experienced by cosmic rays during propagation in the Galaxy. We find that the stochastic fluctuations induced by the spatial and temporal distribution of supernovae, together with the effect of spallation of nuclei, lead to mild but sensible violations of the simple, leaky-box-inspired rule that the spectrum observed at Earth is N(E) proportional to E super(- alpha ) with alpha = gamma + delta , where gamma is the slope of the cosmic ray injection spectrum at the sources. We also comment on the effect of time dependence of the escape of cosmic rays from supernova remnants, and of a possible clustering of the sources in superbubbles.
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ISSN:1475-7516
1475-7516
DOI:10.1088/1475-7516/2012/01/010