Magnetic Field-Line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence
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| Format: | Preprint |
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2025
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| _version_ | 1866917076431536128 |
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| author | Sebastian, Samuel Comisso, Luca |
| author_facet | Sebastian, Samuel Comisso, Luca |
| contents | We employ first-principles, fully kinetic particle-in-cell simulations to investigate magnetic field-line curvature in magnetically dominated turbulent plasmas and its role in particle acceleration through curvature-drift motion along the motional electric field. By varying the fluctuation-to-mean magnetic-field ratio $δB_0/B_0$, we examine curvature $κ$ statistics and their connection to particle acceleration. The curvature probability densities display broad power-law wings, scaling linearly in $κ$ below the peak and developing hard high-$κ$ tails for $δB_0/B_0 \gtrsim 1$. As the mean field strengthens, the high-$κ$ tails steepen, and large-curvature events are suppressed when $δB_0/B_0 \ll 1$. The probability density functions of magnetic field-line contraction, ${\bf v}_E \cdot {\bf κ}$, with ${\bf v}_E$ the field-line velocity, develop power-law tails well described by a symmetric Pareto distribution, characteristic of stochastic energy exchanges, with the tails becoming harder as $δB_0/B_0$ increases. Our guiding-center analysis shows that curvature-drift acceleration accounts for a substantial fraction of the energization via the motional electric field, and that it strengthens with increasing $δB_0/B_0$. For well-magnetized particles, curvature-drift acceleration typically exceeds ${\bf\nabla}B$ drift, polarization drift, and betatron contributions. These results identify curvature-drift acceleration as a principal pathway through which magnetized turbulence transfers energy to nonthermal particles in astrophysical plasmas. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_20628 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Magnetic Field-Line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence Sebastian, Samuel Comisso, Luca High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Plasma Physics We employ first-principles, fully kinetic particle-in-cell simulations to investigate magnetic field-line curvature in magnetically dominated turbulent plasmas and its role in particle acceleration through curvature-drift motion along the motional electric field. By varying the fluctuation-to-mean magnetic-field ratio $δB_0/B_0$, we examine curvature $κ$ statistics and their connection to particle acceleration. The curvature probability densities display broad power-law wings, scaling linearly in $κ$ below the peak and developing hard high-$κ$ tails for $δB_0/B_0 \gtrsim 1$. As the mean field strengthens, the high-$κ$ tails steepen, and large-curvature events are suppressed when $δB_0/B_0 \ll 1$. The probability density functions of magnetic field-line contraction, ${\bf v}_E \cdot {\bf κ}$, with ${\bf v}_E$ the field-line velocity, develop power-law tails well described by a symmetric Pareto distribution, characteristic of stochastic energy exchanges, with the tails becoming harder as $δB_0/B_0$ increases. Our guiding-center analysis shows that curvature-drift acceleration accounts for a substantial fraction of the energization via the motional electric field, and that it strengthens with increasing $δB_0/B_0$. For well-magnetized particles, curvature-drift acceleration typically exceeds ${\bf\nabla}B$ drift, polarization drift, and betatron contributions. These results identify curvature-drift acceleration as a principal pathway through which magnetized turbulence transfers energy to nonthermal particles in astrophysical plasmas. |
| title | Magnetic Field-Line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Plasma Physics |
| url | https://arxiv.org/abs/2510.20628 |