System-size Convergence of Nonthermal Particle Acceleration in Relativistic Plasma Turbulence
[2];
[2];
[3]
- Univ. of Colorado, Boulder, CO (United States), JILA ; National Inst. of Standards and Technology (NIST), Boulder, CO (United States); Princeton Univ., NJ (United States)
- Univ. of Colorado, Boulder, CO (United States). Center for Integrated Plasma Studies
- Univ. of Colorado, Boulder, CO (United States), JILA and Dept. of Astrophysical and Planetary Sciences ; National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
We apply collisionless particle-in-cell simulations of relativistic pair plasmas to explore whether driven turbulence is a viable high-energy astrophysical particle accelerator. We characterize nonthermal particle distributions for varying system sizes up to L/2πρ e0 = 163, where L/2π is the driving scale and ρ e0 is the initial characteristic Larmor radius. We show that turbulent particle acceleration produces power-law energy distributions that, when compared at a fixed number of large-scale dynamical times, slowly steepen with increasing system size. We demonstrate, however, that convergence is obtained by comparing the distributions at different times that increase with system size (approximately logarithmically). We suggest that the system-size dependence arises from the time required for particles to reach the highest accessible energies via Fermi acceleration. The converged power-law index of the energy distribution, α ≈ 3.0 for magnetization σ = 3/8, makes turbulence a possible explanation for nonthermal spectra observed in systems such as the Crab Nebula.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1510325
- Journal Information:
- The Astrophysical Journal. Letters, Vol. 867, Issue 1; ISSN 2041-8213
- Country of Publication:
- United States
- Language:
- English
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