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| Natura: | Preprint |
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2024
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| Accesso online: | https://arxiv.org/abs/2410.05546 |
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| _version_ | 1866912147597950976 |
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| author | Comisso, Luca Farrar, Glennys R. Muzio, Marco S. |
| author_facet | Comisso, Luca Farrar, Glennys R. Muzio, Marco S. |
| contents | Ultra-High-Energy Cosmic Rays (UHECRs), particles characterized by energies exceeding $10^{18}$ eV, are generally believed to be accelerated electromagnetically in high-energy astrophysical sources. One promising mechanism of UHECR acceleration is magnetized turbulence. We demonstrate from first principles, using fully kinetic particle-in-cell simulations, that magnetically dominated turbulence accelerates particles on a short timescale, producing a power-law energy distribution with a rigidity-dependent, sharply defined cutoff well approximated by the form $f_{\rm cut}\left({E, E_{\rm cut}}\right) = {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$. Particle escape from the turbulent accelerating region is energy-dependent, with $t_{\rm esc} \propto E^{-δ}$ and $δ\sim 1/3$. The resulting particle flux from the accelerator follows $dN/dEdt \propto E^{-s} {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$, with $s \sim 2.1$. We fit the Pierre Auger Observatory's spectrum and composition measurements, taking into account particle interactions between acceleration and detection, and show that the turbulence-associated energy cutoff is well supported by the data, with the best-fitting spectral index being $s = 2.1^{+0.06}_{-0.13}$. Our first-principles results indicate that particle acceleration by magnetically dominated turbulence may constitute the physical mechanism responsible for UHECR acceleration. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_05546 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Ultra-High-Energy Cosmic Rays Accelerated by Magnetically Dominated Turbulence Comisso, Luca Farrar, Glennys R. Muzio, Marco S. High Energy Astrophysical Phenomena Plasma Physics Ultra-High-Energy Cosmic Rays (UHECRs), particles characterized by energies exceeding $10^{18}$ eV, are generally believed to be accelerated electromagnetically in high-energy astrophysical sources. One promising mechanism of UHECR acceleration is magnetized turbulence. We demonstrate from first principles, using fully kinetic particle-in-cell simulations, that magnetically dominated turbulence accelerates particles on a short timescale, producing a power-law energy distribution with a rigidity-dependent, sharply defined cutoff well approximated by the form $f_{\rm cut}\left({E, E_{\rm cut}}\right) = {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$. Particle escape from the turbulent accelerating region is energy-dependent, with $t_{\rm esc} \propto E^{-δ}$ and $δ\sim 1/3$. The resulting particle flux from the accelerator follows $dN/dEdt \propto E^{-s} {\text{sech}}\left[ ( {{E}/{E_{\rm cut}}} )^2 \right]$, with $s \sim 2.1$. We fit the Pierre Auger Observatory's spectrum and composition measurements, taking into account particle interactions between acceleration and detection, and show that the turbulence-associated energy cutoff is well supported by the data, with the best-fitting spectral index being $s = 2.1^{+0.06}_{-0.13}$. Our first-principles results indicate that particle acceleration by magnetically dominated turbulence may constitute the physical mechanism responsible for UHECR acceleration. |
| title | Ultra-High-Energy Cosmic Rays Accelerated by Magnetically Dominated Turbulence |
| topic | High Energy Astrophysical Phenomena Plasma Physics |
| url | https://arxiv.org/abs/2410.05546 |