Particle Acceleration in Magnetized Shear-Driven Turbulence
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arXiv
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| Auteurs principaux: | , , , , , , , |
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| Format: | Preprint |
| Publié: |
2025
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| _version_ | 1866911318457450496 |
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| author | Liu, Mingxuan Ruszkowski, Mateusz Zweibel, Ellen Sun, Xiaochen Caprioli, Damiano Liang, Naixin Oh, Siang Peng Spitkovsky, Anatoly |
| author_facet | Liu, Mingxuan Ruszkowski, Mateusz Zweibel, Ellen Sun, Xiaochen Caprioli, Damiano Liang, Naixin Oh, Siang Peng Spitkovsky, Anatoly |
| contents | Shear flows, ubiquitous in space and astrophysical plasmas, can accelerate particles through turbulence excited by the Kelvin-Helmholtz instability. We present the first numerical study of particle acceleration in non-relativistic, magnetized, and purely shear-driven turbulence that includes full particle backreaction. Using two-dimensional MHD-PIC simulations with an initially uniform flow-aligned magnetic field and external stirring force, we demonstrate that sustained particle acceleration requires continuously driven turbulence, whereas freely decaying turbulence rapidly depletes its energy reservoirs and halts the acceleration. The acceleration mechanism operates through the systematic distortion of gyro-orbits by turbulent electric fields: acceleration phases extend the particle trajectory along the electric force, increasing the energy gain, while deceleration phases shorten the trajectory, reducing the energy loss. This asymmetry produces net energy gain despite stochastic fluctuations, with the mean energy change scaling quadratically with shear velocity, characteristic of second-order Fermi acceleration. Initially monoenergetic particles develop substantial non-thermal tails after the turbulence onset. For particles repeatedly crossing shear layers, their energization follows geometric Brownian motion with weak systematic drift, yielding a log-normal distribution. High-energy particles exhibit pitch-angle anisotropy, becoming preferentially perpendicular to the flow-aligned magnetic field as their gyroradii exceed the turbulent layer width. These results establish shear-driven turbulence as a viable particle acceleration mechanism, providing a general model for particle energization in shear flows. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_12720 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Particle Acceleration in Magnetized Shear-Driven Turbulence Liu, Mingxuan Ruszkowski, Mateusz Zweibel, Ellen Sun, Xiaochen Caprioli, Damiano Liang, Naixin Oh, Siang Peng Spitkovsky, Anatoly High Energy Astrophysical Phenomena Shear flows, ubiquitous in space and astrophysical plasmas, can accelerate particles through turbulence excited by the Kelvin-Helmholtz instability. We present the first numerical study of particle acceleration in non-relativistic, magnetized, and purely shear-driven turbulence that includes full particle backreaction. Using two-dimensional MHD-PIC simulations with an initially uniform flow-aligned magnetic field and external stirring force, we demonstrate that sustained particle acceleration requires continuously driven turbulence, whereas freely decaying turbulence rapidly depletes its energy reservoirs and halts the acceleration. The acceleration mechanism operates through the systematic distortion of gyro-orbits by turbulent electric fields: acceleration phases extend the particle trajectory along the electric force, increasing the energy gain, while deceleration phases shorten the trajectory, reducing the energy loss. This asymmetry produces net energy gain despite stochastic fluctuations, with the mean energy change scaling quadratically with shear velocity, characteristic of second-order Fermi acceleration. Initially monoenergetic particles develop substantial non-thermal tails after the turbulence onset. For particles repeatedly crossing shear layers, their energization follows geometric Brownian motion with weak systematic drift, yielding a log-normal distribution. High-energy particles exhibit pitch-angle anisotropy, becoming preferentially perpendicular to the flow-aligned magnetic field as their gyroradii exceed the turbulent layer width. These results establish shear-driven turbulence as a viable particle acceleration mechanism, providing a general model for particle energization in shear flows. |
| title | Particle Acceleration in Magnetized Shear-Driven Turbulence |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2512.12720 |