Kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling
| Autor: | Vladimir Zhdankin, Dmitri A. Uzdensky, Gregory R. Werner, Mitchell C. Begelman |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics Radiative cooling Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences Astronomy and Astrophysics Magnetic reconnection Plasma Kinetic energy 01 natural sciences Physics - Plasma Physics Computational physics Magnetic radiation reaction force Plasma Physics (physics.plasm-ph) Particle acceleration Space and Planetary Science Physics::Space Physics 0103 physical sciences Radiative transfer Astrophysics - High Energy Astrophysical Phenomena 010306 general physics Blazar 010303 astronomy & astrophysics |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 493:603-626 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/staa284 |
| Popis: | High-energy astrophysical systems frequently contain collisionless relativistic plasmas that are heated by turbulent cascades and cooled by emission of radiation. Understanding the nature of this radiative turbulence is a frontier of extreme plasma astrophysics. In this paper, we use particle-in-cell simulations to study the effects of external inverse Compton radiation on turbulence driven in an optically thin, relativistic pair plasma. We focus on the statistical steady state (where injected energy is balanced by radiated energy) and perform a parameter scan spanning from low magnetization to high magnetization ($0.04 \lesssim \sigma \lesssim 11$). We demonstrate that the global particle energy distributions are quasi-thermal in all simulations, with only a modest population of nonthermal energetic particles (extending the tail by a factor of $\sim 2$). This indicates that nonthermal particle acceleration (observed in similar non-radiative simulations) is quenched by strong radiative cooling. The quasi-thermal energy distributions are well fit by analytic models in which stochastic particle acceleration (due to, e.g., second-order Fermi mechanism or gyroresonant interactions) is balanced by the radiation reaction force. Despite the efficient thermalization of the plasma, nonthermal energetic particles do make a conspicuous appearance in the anisotropy of the global momentum distribution as highly variable, intermittent beams (for high magnetization cases). The beamed high-energy particles are spatially coincident with intermittent current sheets, suggesting that localized magnetic reconnection may be a mechanism for kinetic beaming. This beaming phenomenon may explain rapid flares observed in various astrophysical systems (such as blazar jets, the Crab nebula, and Sagittarius A*). Comment: 26 pages, 30 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society |
| Databáze: | OpenAIRE |
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