Maximum Particle Energy by Fermi Acceleration in Relativistic Flows
نویسنده
چکیده
An expression for maximum accelerated particle energy Emax due to the firstorder shock-Fermi process is generalized to relativistic flows. Given the Bohm diffusion approximation and a mean ISM magnetic field of 3μG, then Emax ≈ 8 × 10β0Z(m⊙/n0) 1/3 eV for an uncollimated explosion expanding into a uniform medium with density n0. The initial flow speed of the explosion is β0c, and the total ejecta energy, in Solar rest-mass energy units, is m⊙. Second-order stochastic processes in relativistic flows can accelerate cosmic rays to ultra-high energies. Sources of mildly relativistic or relativistic flows with adequate power, namely fireball transients and gamma-ray bursts, are proposed as the sources of cosmic rays near and above the knee of the cosmic-ray spectrum. Subject headings: cosmic rays — gamma ray bursts — particle acceleration
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