On the Energy Spectra of GeV/TeV Cosmic Ray Leptons Metadata

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Title

  • Main Title On the Energy Spectra of GeV/TeV Cosmic Ray Leptons

Creator

  • Author: Stawarz, Lukasz
    Creator Type: Personal
  • Author: /KIPAC, Menlo Park /Jagiellonian U., Astron. Observ.
    Creator Type: Personal
  • Author: Petrosian, Vahe
    Creator Type: Personal
  • Author: /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.
    Creator Type: Personal
  • Author: Blandford, Roger D.
    Creator Type: Personal
  • Author: /KIPAC, Menlo Park
    Creator Type: Personal

Contributor

  • Sponsor: United States. Department of Energy.
    Contributor Type: Organization

Publisher

  • Name: SLAC National Accelerator Laboratory
    Place of Publication: United States
    Additional Info: SLAC National Accelerator Laboratory (SLAC)

Date

  • Creation: 2011-08-19

Language

  • English

Description

  • Content Description: Recent observations of cosmic ray electrons from several instruments have revealed various degrees of deviation in the measured electron energy distribution from a simple power-law, in a form of an excess around 0.1 to 1 TeV energies. An even more prominent deviation and excess has been observed in the fraction of cosmic ray positrons around 10 and 100 GeV energies. These observations have received considerable attention and many theoretical models have been proposed to explain them. The models rely on either dark matter annihilation/decay or specific nearby astrophysical sources, and involve several additional assumptions regarding the dark matter distribution or particle acceleration. In this paper we show that the observed excesses in the electron spectrum may be easily reproduced without invoking any unusual sources other than the general diffuse Galactic components of cosmic rays. The model presented here assumes a power-law injection of electrons (and protons) by supernova remnants, and evaluates their expected energy spectrum based on a simple kinetic equation describing the propagation of charged particles in the interstellar medium. The primary physical effect involved is the Klein-Nishina suppression of the electron cooling rate around TeV energies. With a very reasonable choice of the model parameters characterizing the local interstellar medium, we can reproduce the most recent observations by Fermi and HESS experiments. Interestingly, in our model the injection spectral index of cosmic ray electrons becomes comparable to, or even equal to that of cosmic ray protons. The Klein-Nishina effect may also affect the propagation of the secondary e{sup {+-}} pairs, and therefore modify the cosmic ray positron-to-electron ratio. We have explored this possibility by considering two mechanisms for production of e{sup {+-}} pairs within the Galaxy. The first is due to the decay of {pi}{sup {+-}}'s produced by interaction of cosmic ray nuclei with ambient protons. The second source discussed here is due to the annihilation of the diffuse Galactic {gamma}-rays on the stellar photon field. We find that high positron fraction increasing with energy, as claimed by the PAMELA experiment, cannot be explained in our model with the conservative set of the model parameters. We are able, however, to reproduce the PAMELA (as well as Fermi and HESS) results assuming high values of the starlight and interstellar gas densities, which would be more appropriate for vicinities of supernova remnants. A possible solution to this problem may be that cosmic rays undergo most of their interactions near their sources due to the efficient trapping in the far upstream of supernova shocks by self-generated, cosmic ray-driven turbulence.
  • Physical Description: 28 pages

Subject

  • Keyword: Charged Particles
  • Keyword: Nonluminous Matter
  • Keyword: Turbulence Astrophysics,Astro
  • STI Subject Categories: 72 Physics Of Elementary Particles And Fields
  • Keyword: Leptons
  • Keyword: Supernova Remnants
  • STI Subject Categories: 73 Nuclear Physics And Radiation Physics
  • Keyword: Kinetic Equations
  • Keyword: Protons
  • Keyword: Annihilation
  • Keyword: Electrons
  • Keyword: Distribution
  • Keyword: Electron Cooling
  • Keyword: Positrons
  • Keyword: Astrophysics,Astro
  • Keyword: Trapping
  • Keyword: Acceleration
  • Keyword: Nuclei
  • Keyword: Decay
  • Keyword: Photons
  • Keyword: Energy Spectra
  • STI Subject Categories: 71 Classical And Quantum Mechanics, General Physics
  • Keyword: Production

Source

  • Journal Name: Astrophys.J.710:236-247,2010

Collection

  • Name: Office of Scientific & Technical Information Technical Reports
    Code: OSTI

Institution

  • Name: UNT Libraries Government Documents Department
    Code: UNTGD

Resource Type

  • Article

Format

  • Text

Identifier

  • Report No.: SLAC-PUB-13883
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 1022503
  • Archival Resource Key: ark:/67531/metadc835288

Note

  • Display Note: http://www.slac.stanford.edu/cgi-wrap/pubpage?slac-pub-13883.html
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