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Martin Lemoine - One of the best experts on this subject based on the ideXlab platform.

  • Particle Acceleration in relativistic turbulence: A theoretical appraisal
    Physical Review D, 2020
    Co-Authors: Camilia Demidem, Martin Lemoine, Fabien Casse
    Abstract:

    We discuss the physics of stochastic Particle Acceleration in relativistic magnetohydrodynamic (MHD) turbulence, combining numerical simulations of test-Particle Acceleration in synthetic wave turbulence spectra with detailed analytical estimates. In particular, we study Particle Acceleration in wavelike isotropic fast mode turbulence, in Alfv\'en and slow Goldreich-Sridhar type wave turbulence (properly accounting for anisotropy effects), including resonance broadening due to wave decay and pitch-angle randomization. At high Particle rigidities, the contributions of those three modes to Acceleration are comparable to within an order of magnitude, as a combination of several effects (partial disappearance of transit-time damping for fast modes, increased scattering rate for Alfv\'en and slow modes due to resonance broadening). Additionally, we provide analytical arguments regarding Acceleration beyond the regime of MHD wave turbulence, addressing the issue of nonresonant Acceleration in a turbulence comprised of structures rather than waves, as well as the issue of Acceleration in small-scale parallel electric fields. Finally, we compare our results to the existing literature and provide ready-to-use formulas for applications to high-energy astrophysical phenomenology.

  • Particle Acceleration in relativistic turbulence: a theoretical appraisal
    2019
    Co-Authors: Camilia Demidem, Martin Lemoine, Fabien Casse
    Abstract:

    We discuss the physics of stochastic Particle Acceleration in relativistic MHD turbulence, combining numerical simulations of test-Particle Acceleration in synthetic wave turbulence spectra with detailed analytical estimates. In particular, we study Particle Acceleration in wave-like isotropic fast mode turbulence, in Alfv\'en and slow Goldreich-Sridhar type wave turbulence (properly accounting for local anisotropy effects), including resonance broadening due to wave decay and pitch-angle randomization. At high Particle rigidities, the contributions of those three modes to Acceleration are comparable to within an order of magnitude, as a combination of several effects (partial disappearance of transit-time damping for fast modes, increased scattering rate for Alfv\'en and slow modes due to resonance broadening). Additionally, we provide analytical arguments regarding Acceleration beyond the regime of MHD wave turbulence, addressing the issue of non-resonant Acceleration in a turbulence comprised of structures rather than waves, as well as the issue of Acceleration in small-scale parallel electric fields. Finally, we compare our results to the existing literature and provide ready-to-use formulas for applications to high-energy astrophysical phenomenology.

  • Particle Acceleration at relativistic shock waves
    2017
    Co-Authors: Martin Lemoine, Guy Pelletier
    Abstract:

    International audienceThis paper reviews our current understanding of the physics of Particle Acceleration at relativistic shock waves, emphasizing in particular the intimate link between the Acceleration of Particles and the generation of turbulence, as well as the importance of microphysics for phenomenology

  • Particle Acceleration at relativistic shock waves
    2016
    Co-Authors: Martin Lemoine, Ghyslain Pelletier
    Abstract:

    This paper reviews our current understanding of the physics of Particle Acceleration at relativistic shock waves, emphasizing in particular the intimate link between the Acceleration of Particles and the generation of turbulence, as well as the importance of microphysics for phenomenology.

  • Relativistic Shocks: Particle Acceleration and Magnetization
    Space Science Reviews, 2015
    Co-Authors: L. Sironi, U. Keshet, Martin Lemoine
    Abstract:

    We review the physics of relativistic shocks, which are often invoked as the sources of non-thermal Particles in pulsar wind nebulae (PWNe), gamma-ray bursts (GRBs), and active galactic nuclei (AGN) jets, and as possible sources of ultra-high energy cosmic-rays. We focus on Particle Acceleration and magnetic field generation, and describe the recent progress in the field driven by theory advances and by the rapid development of Particle-in-cell (PIC) simulations. In weakly magnetized or quasi parallel-shocks (i.e. where the magnetic field is nearly aligned with the flow), Particle Acceleration is efficient. The accelerated Particles stream ahead of the shock, where they generate strong magnetic waves which in turn scatter the Particles back and forth across the shock, mediating their Acceleration. In contrast, in strongly magnetized quasi-perpendicular shocks, the efficiencies of both Particle Acceleration and magnetic field generation are suppressed. Particle Acceleration, when efficient, modifies the turbulence around the shock on a long time scale, and the accelerated Particles have a characteristic energy spectral index of s γ ≃ 2.2 $s_{\gamma}\simeq2.2$ in the ultra-relativistic limit. We discuss how this novel understanding of Particle Acceleration and magnetic field generation in relativistic shocks can be applied to high-energy astrophysical phenomena, with an emphasis on PWNe and GRB afterglows.

M. Hoshino - One of the best experts on this subject based on the ideXlab platform.

  • angular momentum transport and Particle Acceleration during magnetorotational instability in a kinetic accretion disk
    Physical Review Letters, 2015
    Co-Authors: M. Hoshino
    Abstract:

    Angular momentum transport and Particle Acceleration during the magnetorotational instability (MRI) in a collisionless accretion disk are investigated using three-dimensional Particle-in-cell simulation. We show that the kinetic MRI can provide not only high-energy Particle Acceleration but also enhancement of angular momentum transport. We find that the plasma pressure anisotropy inside the channel flow with p(∥)>p(⊥) induced by active magnetic reconnection suppresses the onset of subsequent reconnection, which, in turn, leads to high-magnetic-field saturation and enhancement of the Maxwell stress tensor of angular momentum transport. Meanwhile, during the quiescent stage of reconnection, the plasma isotropization progresses in the channel flow and the anisotropic plasma with p(⊥)>p(∥) due to the dynamo action of MRI outside the channel flow contribute to rapid reconnection and strong Particle Acceleration. This efficient Particle Acceleration and enhanced angular momentum transport in a collisionless accretion disk may explain the origin of high-energy Particles observed around massive black holes.

  • Relativistic Reconnection and Particle Acceleration
    Space Science Reviews, 2012
    Co-Authors: M. Hoshino, Y. Lyubarsky
    Abstract:

    This chapter mainly deals with magnetic reconnection and Particle Acceleration in relativistic astrophysical plasmas, where the temperature of the current sheet exceeds the rest mass energy and the Alfvén velocity is close to the speed of light. Magnetic reconnection now receives a great deal of interest for its role in many astrophysical systems such as pulsars, magnetars, galaxy clusters, and active galactic nucleus jets. We review recent advances that emphasize the roles of reconnection in high-energy astrophysical phenomena.

  • Relativistic Reconnection and Particle Acceleration
    Space Science Reviews, 2012
    Co-Authors: M. Hoshino, Y. Lyubarsky
    Abstract:

    This chapter mainly deals with magnetic reconnection and Particle Acceleration in relativistic astrophysical plasmas, where the temperature of the current sheet exceeds the rest mass energy and the Alfven velocity is close to the speed of light. Magnetic reconnection now receives a great deal of interest for its role in many astrophysical systems such as pulsars, magnetars, galaxy clusters, and active galactic nucleus jets. We review recent advances that emphasize the roles of reconnection in high-energy astrophysical phenomena.

  • Direct Particle Acceleration in Astroplasmas
    AIP Conference Proceedings, 2002
    Co-Authors: M. Hoshino
    Abstract:

    The high energy Particle Acceleration mechanisms are discussed by focusing on the direct Acceleration in the astrophysical context. We specifically argue that the relativistic magnetic reconnection and the shock surfing/surfatron processes can efficiently accelerate charged Particles to a relativistic energy, and that those mechanisms may produce a non‐thermal, power‐law energy spectrum.

Y. Lyubarsky - One of the best experts on this subject based on the ideXlab platform.

  • Relativistic Reconnection and Particle Acceleration
    Space Science Reviews, 2012
    Co-Authors: M. Hoshino, Y. Lyubarsky
    Abstract:

    This chapter mainly deals with magnetic reconnection and Particle Acceleration in relativistic astrophysical plasmas, where the temperature of the current sheet exceeds the rest mass energy and the Alfvén velocity is close to the speed of light. Magnetic reconnection now receives a great deal of interest for its role in many astrophysical systems such as pulsars, magnetars, galaxy clusters, and active galactic nucleus jets. We review recent advances that emphasize the roles of reconnection in high-energy astrophysical phenomena.

  • Relativistic Reconnection and Particle Acceleration
    Space Science Reviews, 2012
    Co-Authors: M. Hoshino, Y. Lyubarsky
    Abstract:

    This chapter mainly deals with magnetic reconnection and Particle Acceleration in relativistic astrophysical plasmas, where the temperature of the current sheet exceeds the rest mass energy and the Alfven velocity is close to the speed of light. Magnetic reconnection now receives a great deal of interest for its role in many astrophysical systems such as pulsars, magnetars, galaxy clusters, and active galactic nucleus jets. We review recent advances that emphasize the roles of reconnection in high-energy astrophysical phenomena.

Yuri E. Litvinenko - One of the best experts on this subject based on the ideXlab platform.

  • Time-dependent Particle Acceleration in a Fermi reservoir
    Astronomy & Astrophysics, 2012
    Co-Authors: Yuri E. Litvinenko
    Abstract:

    Context. A steady model was presented by Burn, in which energy conservation is used to constrain the parameters of stochastic Fermi Acceleration. A steady model, however, is unlikely to be adequate for Particle Acceleration in impulsive solar flares. Aims. This paper describes a time-dependent model for Particle Acceleration in a Fermi reservoir Methods. The calculation is based on the original formulation of stochastic Acceleration by Fermi, with additional physically motivated assumptions about the turbulent and Particle energy densities within the reservoir, that are similar to those of the steady analysis. The problem is reduced to an integro-differential equation that possesses an analytical solution. Results. The model predicts the formation of a power-law differential energy spectrum N(E) ∼ E−2, that is observable outside the reservoir. The predicted spectral index is independent of the parameters of the model. The results may help in understanding Particle Acceleration in solar flares and other astrophysical applications.

  • Time-dependent Particle Acceleration in a Fermi reservoir (Research Note)
    2012
    Co-Authors: Yuri E. Litvinenko
    Abstract:

    Context. A steady model was presented by Burn, in which energy conservation is used to constrain the parameters of stochastic Fermi Acceleration. A steady model, however, is unlikely to be adequate for Particle Acceleration in impulsive solar flares. Aims. This paper describes a time-dependent model for Particle Acceleration in a Fermi reservoir Methods. The calculation is based on the original formulation of stochastic Acceleration by Fermi, with additional physically motivated assumptions about the turbulent and Particle energy densities within the reservoir, that are similar to those of the steady analysis. The problem is reduced to an integro-differential equation that possesses an analytical solution. Results. The model predicts the formation of a power-law differential energy spectrum N(E) ∼ E −2 , that is observable outside the reservoir. The predicted spectral index is independent of the parameters of the model. The results may help in understanding Particle Acceleration in solar flares and other astrophysical applications.

  • Particle Acceleration Scalings Based on Exact Analytic Models for Magnetic Reconnection
    The Astrophysical Journal, 2002
    Co-Authors: Ian J.d. Craig, Yuri E. Litvinenko
    Abstract:

    Observations suggest that Particle Acceleration in solar flares occurs in the magnetic reconnection region above the flare loops. Theoretical models for Particle Acceleration by the reconnection electric field, however, employ heuristic configurations for electric and magnetic fields in model current sheets, which are not solutions to the MHD reconnection problem. In the present study, Particle Acceleration is discussed within the context of a self-consistent MHD reconnection solution. This has the advantage of allowing poorly constrained local parameters in the current sheet region to be expressed in terms of the boundary conditions and electric resistivity of the global solution. The resulting Acceleration model leads to energy gains that are consistent with those for high-energy Particles in solar flares. The overall self-consistency of the approach is discussed.

Fabien Casse - One of the best experts on this subject based on the ideXlab platform.

  • Particle Acceleration in relativistic turbulence: A theoretical appraisal
    Physical Review D, 2020
    Co-Authors: Camilia Demidem, Martin Lemoine, Fabien Casse
    Abstract:

    We discuss the physics of stochastic Particle Acceleration in relativistic magnetohydrodynamic (MHD) turbulence, combining numerical simulations of test-Particle Acceleration in synthetic wave turbulence spectra with detailed analytical estimates. In particular, we study Particle Acceleration in wavelike isotropic fast mode turbulence, in Alfv\'en and slow Goldreich-Sridhar type wave turbulence (properly accounting for anisotropy effects), including resonance broadening due to wave decay and pitch-angle randomization. At high Particle rigidities, the contributions of those three modes to Acceleration are comparable to within an order of magnitude, as a combination of several effects (partial disappearance of transit-time damping for fast modes, increased scattering rate for Alfv\'en and slow modes due to resonance broadening). Additionally, we provide analytical arguments regarding Acceleration beyond the regime of MHD wave turbulence, addressing the issue of nonresonant Acceleration in a turbulence comprised of structures rather than waves, as well as the issue of Acceleration in small-scale parallel electric fields. Finally, we compare our results to the existing literature and provide ready-to-use formulas for applications to high-energy astrophysical phenomenology.

  • Particle Acceleration in relativistic turbulence: a theoretical appraisal
    2019
    Co-Authors: Camilia Demidem, Martin Lemoine, Fabien Casse
    Abstract:

    We discuss the physics of stochastic Particle Acceleration in relativistic MHD turbulence, combining numerical simulations of test-Particle Acceleration in synthetic wave turbulence spectra with detailed analytical estimates. In particular, we study Particle Acceleration in wave-like isotropic fast mode turbulence, in Alfv\'en and slow Goldreich-Sridhar type wave turbulence (properly accounting for local anisotropy effects), including resonance broadening due to wave decay and pitch-angle randomization. At high Particle rigidities, the contributions of those three modes to Acceleration are comparable to within an order of magnitude, as a combination of several effects (partial disappearance of transit-time damping for fast modes, increased scattering rate for Alfv\'en and slow modes due to resonance broadening). Additionally, we provide analytical arguments regarding Acceleration beyond the regime of MHD wave turbulence, addressing the issue of non-resonant Acceleration in a turbulence comprised of structures rather than waves, as well as the issue of Acceleration in small-scale parallel electric fields. Finally, we compare our results to the existing literature and provide ready-to-use formulas for applications to high-energy astrophysical phenomenology.