Beyond Fermi-II: Intermittent Particle Acceleration by Relativistic Turbulence in Astrophysical Plasmas
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arXiv
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| Autores principales: | , , |
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| Formato: | Preprint |
| Publicado: |
2026
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| _version_ | 1866914381134036992 |
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| author | Dmytriiev, Anton van der Merwe, Frans Böttcher, Markus |
| author_facet | Dmytriiev, Anton van der Merwe, Frans Böttcher, Markus |
| contents | Stochastic particle acceleration in turbulent plasmas plays a key role in shaping high-energy emission from relativistic outflows, such as those in Active Galactic Nuclei (AGN) and microquasars. While traditional Fermi-II models provide a foundational framework, they often oversimplify the complex nature of realistic magnetohydrodynamic (MHD) turbulence, especially in high-amplitude ($δB/B_0 \sim 1$) and relativistic regimes. Recent plasma simulations for these conditions have revealed highly non-linear energization effects, such as sudden, large momentum jumps, that remain largely unexplored in astrophysical applications. We present a novel Monte Carlo framework STRIPE that models particle acceleration as a continuous-time random walk (CTRW), capturing both intermittent energy gains and radiative losses. The stochastic evolution of particle momenta is driven by jumps with random magnitudes determined by a distribution of magnetic-field-line velocity gradients, with synchrotron and inverse Compton cooling incorporated self-consistently. Using STRIPE, we explore particle acceleration under physical conditions characteristic of TeV-PeV $γ$-ray emitting microquasars recently identified by Large High Altitude Air Shower Observatory (LHAASO). We find that relativistic, high-amplitude turbulence naturally produces particle spectra with steep low-energy cutoffs, and hard extended power-law high-energy tails reaching tens of PeV. These features differ markedly from standard quasi-linear theory and are well suited to explaining the unexpectedly hard TeV-PeV spectra of LHAASO-detected microquasars. These results highlight turbulent acceleration in the relativistic regime as a promising mechanism for particle energization in microquasar systems, as well as potentially other extreme astrophysical environments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_09394 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Beyond Fermi-II: Intermittent Particle Acceleration by Relativistic Turbulence in Astrophysical Plasmas Dmytriiev, Anton van der Merwe, Frans Böttcher, Markus High Energy Astrophysical Phenomena Stochastic particle acceleration in turbulent plasmas plays a key role in shaping high-energy emission from relativistic outflows, such as those in Active Galactic Nuclei (AGN) and microquasars. While traditional Fermi-II models provide a foundational framework, they often oversimplify the complex nature of realistic magnetohydrodynamic (MHD) turbulence, especially in high-amplitude ($δB/B_0 \sim 1$) and relativistic regimes. Recent plasma simulations for these conditions have revealed highly non-linear energization effects, such as sudden, large momentum jumps, that remain largely unexplored in astrophysical applications. We present a novel Monte Carlo framework STRIPE that models particle acceleration as a continuous-time random walk (CTRW), capturing both intermittent energy gains and radiative losses. The stochastic evolution of particle momenta is driven by jumps with random magnitudes determined by a distribution of magnetic-field-line velocity gradients, with synchrotron and inverse Compton cooling incorporated self-consistently. Using STRIPE, we explore particle acceleration under physical conditions characteristic of TeV-PeV $γ$-ray emitting microquasars recently identified by Large High Altitude Air Shower Observatory (LHAASO). We find that relativistic, high-amplitude turbulence naturally produces particle spectra with steep low-energy cutoffs, and hard extended power-law high-energy tails reaching tens of PeV. These features differ markedly from standard quasi-linear theory and are well suited to explaining the unexpectedly hard TeV-PeV spectra of LHAASO-detected microquasars. These results highlight turbulent acceleration in the relativistic regime as a promising mechanism for particle energization in microquasar systems, as well as potentially other extreme astrophysical environments. |
| title | Beyond Fermi-II: Intermittent Particle Acceleration by Relativistic Turbulence in Astrophysical Plasmas |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2603.09394 |