Particle Acceleration by Pickup Process Upstream of Relativistic Shocks
Nov 10, 202114 pages
Published in:
- Astrophys.J. 924 (2022) 2, 108,
- Astrophys.J. 924 (2022) 2
- Published: Jan 18, 2022
e-Print:
- 2111.05903 [astro-ph.HE]
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Abstract: (IOP)
Particle acceleration at magnetized purely perpendicular relativistic shocks in electron–ion plasmas is studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor γ
≫ 1 are known to emit intense electromagnetic waves from the shock front, which induce electrostatic plasma waves (wakefield) and transverse filamentary structures in the upstream region via stimulated/induced Raman scattering and filamentation instability, respectively. The wakefield and filaments inject a fraction of the incoming particles into a particle acceleration process, in which particles are once decoupled from the upstream bulk flow by the wakefield, and are picked up again by the flow. The picked-up particles are accelerated by the motional electric field. The maximum attainable Lorentz factor is estimated as for electrons and for ions, where α ∼ 10 is determined from our simulation results. α can increase up to γ
for a weakly magnetized shock if γ
is sufficiently large. This result indicates that highly relativistic astrophysical shocks such as external shocks of gamma-ray bursts can be an efficient particle accelerator.Note:
- 14 pages, 13 figures, accepted to ApJ
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