Diffusion of relativistic charged particles and field lines in isotropic turbulence: I. Numerical simulations
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arXiv
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2022
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| author | Kuhlen, Marco Phan, Vo Hong Minh Mertsch, Philipp |
| author_facet | Kuhlen, Marco Phan, Vo Hong Minh Mertsch, Philipp |
| contents | The transport of non-thermal particles across a large-scale magnetic field in the presence of magnetised turbulence has been a long-standing issue in high-energy astrophysics. Of particular interest is the dependence of the parallel and perpendicular mean free paths $λ_{\parallel}$ and $λ_{\perp}$ on rigidity $\mathcal{R}$. We have revisited this important issue with a view to applications from the transport of Galactic cosmic rays to acceleration at astrophysical shocks. We have run test particle simulations of cosmic ray transport in synthetic, isotropic Kolmogorov turbulence at unprecedentedly low reduced rigidities $\rg/\Lc \simeq 10^{-4}$, corresponding to $\mathcal{R} \simeq 10 \, \text{TV}$ for a turbulent magnetic field of $\Brms = 4 \, μ\text{G}$ and correlation length $\Lc = 30 \, \text{pc}$. Extracting the (asymptotic) parallel and perpendicular mean free paths $λ_{\parallel}$ and $λ_{\perp}$, we have found $λ_{\parallel} \propto (\rg/\Lc)^{1/3}$ as expected for a Kolmogorov turbulence spectrum. In contrast, $λ_{\perp}$ has a faster dependence on $\rg/\Lc$ for $10^{-2} \lesssim \rg/\Lc \lesssim 1$, but for $\rg/\Lc \ll 10^{-2}$, also $λ_{\perp} \propto (\rg/\Lc)^{1/3}$. Our results have important implications for the transport of Galactic cosmic rays. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2211_05881 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Diffusion of relativistic charged particles and field lines in isotropic turbulence: I. Numerical simulations Kuhlen, Marco Phan, Vo Hong Minh Mertsch, Philipp High Energy Astrophysical Phenomena Astrophysics of Galaxies Solar and Stellar Astrophysics The transport of non-thermal particles across a large-scale magnetic field in the presence of magnetised turbulence has been a long-standing issue in high-energy astrophysics. Of particular interest is the dependence of the parallel and perpendicular mean free paths $λ_{\parallel}$ and $λ_{\perp}$ on rigidity $\mathcal{R}$. We have revisited this important issue with a view to applications from the transport of Galactic cosmic rays to acceleration at astrophysical shocks. We have run test particle simulations of cosmic ray transport in synthetic, isotropic Kolmogorov turbulence at unprecedentedly low reduced rigidities $\rg/\Lc \simeq 10^{-4}$, corresponding to $\mathcal{R} \simeq 10 \, \text{TV}$ for a turbulent magnetic field of $\Brms = 4 \, μ\text{G}$ and correlation length $\Lc = 30 \, \text{pc}$. Extracting the (asymptotic) parallel and perpendicular mean free paths $λ_{\parallel}$ and $λ_{\perp}$, we have found $λ_{\parallel} \propto (\rg/\Lc)^{1/3}$ as expected for a Kolmogorov turbulence spectrum. In contrast, $λ_{\perp}$ has a faster dependence on $\rg/\Lc$ for $10^{-2} \lesssim \rg/\Lc \lesssim 1$, but for $\rg/\Lc \ll 10^{-2}$, also $λ_{\perp} \propto (\rg/\Lc)^{1/3}$. Our results have important implications for the transport of Galactic cosmic rays. |
| title | Diffusion of relativistic charged particles and field lines in isotropic turbulence: I. Numerical simulations |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2211.05881 |