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Bacchini F, Zhdankin V, Gorbunov EA, Werner GR, Arzamasskiy L, Begelman MC, Uzdensky DA. Collisionless Magnetorotational Turbulence in Pair Plasmas: Steady-State Dynamics, Particle Acceleration, and Radiative Cooling. PHYSICAL REVIEW LETTERS 2024; 133:045202. [PMID: 39121430 DOI: 10.1103/physrevlett.133.045202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 06/14/2024] [Indexed: 08/11/2024]
Abstract
We present 3D fully kinetic shearing-box simulations of pair-plasma magnetorotational turbulence with unprecedented macro-to-microscopic scale separation. While retrieving the expected fluid behavior of the plasma at large scales, we observe a steepening of turbulent spectra at kinetic scales and substantial angular-momentum transport linked with kinetic processes. For the first time, we provide a definitive demonstration of nonthermal particle acceleration in kinetic magnetorotational turbulence agnostically of shearing-box initial conditions by means of a novel strategy exploiting synchrotron cooling.
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Affiliation(s)
| | | | - Evgeny A Gorbunov
- Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
| | | | | | - Mitchell C Begelman
- JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309-0440, USA
- Department of Astrophysical and Planetary Sciences, University of Colorado, 391 UCB, Boulder, Colorado 80309-0391, USA
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Grošelj D, Hakobyan H, Beloborodov AM, Sironi L, Philippov A. Radiative Particle-in-Cell Simulations of Turbulent Comptonization in Magnetized Black-Hole Coronae. PHYSICAL REVIEW LETTERS 2024; 132:085202. [PMID: 38457737 DOI: 10.1103/physrevlett.132.085202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 09/30/2023] [Accepted: 01/24/2024] [Indexed: 03/10/2024]
Abstract
We report results from the first radiative particle-in-cell simulations of strong Alfvénic turbulence in plasmas of moderate optical depth. The simulations are performed in a local 3D periodic box and self-consistently follow the evolution of radiation as it interacts with a turbulent electron-positron plasma via Compton scattering. We focus on the conditions expected in magnetized coronae of accreting black holes and obtain an emission spectrum consistent with the observed hard state of Cyg X-1. Most of the turbulence power is transferred directly to the photons via bulk Comptonization, shaping the peak of the emission around 100 keV. The rest is released into nonthermal particles, which generate the MeV spectral tail. The method presented here shows promising potential for ab initio modeling of various astrophysical sources and opens a window into a new regime of kinetic plasma turbulence.
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Affiliation(s)
- Daniel Grošelj
- Centre for mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, B-3001 Leuven, Belgium
- Department of Astronomy and Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA
| | - Hayk Hakobyan
- Computational Sciences Department, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
- Department of Physics and Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA
| | - Andrei M Beloborodov
- Department of Physics and Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA
- Max Planck Institute for Astrophysics, D-85741 Garching, Germany
| | - Lorenzo Sironi
- Department of Astronomy and Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA
| | - Alexander Philippov
- Department of Physics, University of Maryland, College Park, Maryland 20742, USA
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Gong Z, Shen X, Hatsagortsyan KZ, Keitel CH. Electron Slingshot Acceleration in Relativistic Preturbulent Shocks Explored via Emitted Photon Polarization. PHYSICAL REVIEW LETTERS 2023; 131:225101. [PMID: 38101383 DOI: 10.1103/physrevlett.131.225101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 09/23/2023] [Accepted: 10/23/2023] [Indexed: 12/17/2023]
Abstract
Transient electron dynamics near the interface of counterstreaming plasmas at the onset of a relativistic collisionless shock (RCS) is investigated using particle-in-cell simulations. We identify a slingshotlike injection process induced by the drifting electric field sustained by the flowing focus of backward-moving electrons, which is distinct from the well-known stochastic acceleration. The flowing focus signifies the plasma kinetic transition from a preturbulent laminar motion to a chaotic turbulence. We find a characteristic correlation between the electron dynamics in the slingshot acceleration and the photon emission features. In particular, the integrated radiation from the RCS exhibits a counterintuitive nonmonotonic dependence of the photon polarization degree on the photon energy, which originates from a polarization degradation of relatively high-energy photons emitted by the slingshot-injected electrons. Our results demonstrate the potential of photon polarization as an essential information source in exploring intricate transient dynamics in RCSs with relevance for Earth-based plasma and astrophysical scenarios.
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Affiliation(s)
- Zheng Gong
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | - Xiaofei Shen
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
| | | | - Christoph H Keitel
- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
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