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High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources
Pasquale Blasi1,2, Elena Amato1, Marta D'Angelo2
1INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy.
Physical Review Letters
|October 3, 2015
Summary
Ultrahigh-energy cosmic rays are confined near their extra-Galactic sources due to plasma instabilities. These instabilities create magnetic fluctuations that scatter particles, limiting their escape energy.
Area of Science:
- Astrophysics
- Plasma Physics
Background:
- Ultrahigh-energy cosmic rays (UHECRs) are primarily accelerated in extra-Galactic sources.
- The high luminosity of these sources implies a significant electric current associated with the cosmic ray flux.
Purpose of the Study:
- To investigate the self-confinement mechanism of cosmic rays within their source regions.
- To determine the energy cutoff (E_cut) for cosmic ray confinement based on source luminosity and magnetic field properties.
Main Methods:
- Theoretical analysis of plasma instabilities driven by cosmic ray currents.
- Modeling magnetic field fluctuations generated by these instabilities.
- Derivation of confinement conditions based on particle scattering.
Main Results:
- Plasma instabilities create magnetic fluctuations that efficiently scatter cosmic rays.
- Cosmic rays are self-confined near sources for energies below a cutoff (E_cut).
- The cutoff energy depends on source luminosity (L44) and background magnetic field strength (B0) and coherence length (λ10).
Conclusions:
- Self-confinement is a crucial factor limiting the propagation of UHECRs from their sources.
- The derived E_cut formulas provide quantitative predictions for UHECR source properties.
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