53,532 research outputs found
Non-linear cosmic ray Galactic transport in the light of AMS-02 and Voyager data
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, such 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
datasets 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
to the grammage, that we argue may come from the sources themselves
Results: A break in the spectra of all nuclei is found at 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 normalisation are free parameters. Moreover, at
rigidities below a few GV, CRs are predicted to be advected with the
self-generated waves at the local Alfv\'en 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.Comment: Submitted to A&A Research Note, 5 pages, 4 Figures. arXiv admin note:
text overlap with arXiv:1306.201
Dark matter distribution in the universe and ultra-high energy cosmic rays
Two of the greatest mysteries of modern physics are the origin of the dark
matter in the universe and the nature of the highest energy particles in the
cosmic ray spectrum. We discuss here possible direct and indirect connections
between these two problems, with particular attention to two cases: in the
first we study the local clustering of possible sources of ultra-high energy
cosmic rays (UHECRs) driven by the local dark matter overdensity. In the second
case we study the possibility that UHECRs are directly generated by the decay
of weakly unstable super heavy dark matter.Comment: 15 pages, 7 figures. Invited Talk at the "International Workshop on
observing UHECRs from space and earth", August 9-12, 2000, Metepec, Puebla
(Mexico
Origin of very high and ultra high energy cosmic rays
While there is some level of consensus on a Galactic origin of cosmic rays up
to the knee ( eV) and on an extragalactic origin of
cosmic rays with energy above eV, the debate on the genesis of
cosmic rays in the intermediate energy region has received much less attention,
mainly because of the ambiguity intrinsic in defining such a region. The energy
range between eV and eV is likely to be the place
where the transition from Galactic to extragalactic cosmic rays takes place.
Hence the origin of these particles, though being of the highest importance
from the physics point of view, it is also one of the most difficult aspects to
investigate. Here I will illustrate some ideas concerning the sites of
acceleration of these particles and the questions that their investigation may
help answer, including the origin of \underline{ultra} high energy cosmic rays.Comment: Solicited Review Paper to appear in 'Comptes Rendus Physique
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