Resonance-broadened Transit Time Damping of Particles in MHD Turbulence

Lazarían, A.

doi:10.3847/1538-4357/aae840

Cited by 47 publications

(45 citation statements)

References 43 publications

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“…Such effects are important not only for the incompressive (Alfvénic) turbulences, but also for the compressive turbulences. Based on Völk (1975), Yan & Lazarian (2008) have shown that the mirror force broadens the resonance condition of the TTD in compressive MHD turbulence (see also Xu & Lazarian 2018). This broadening mechanism is shown to be important also for the SA in this paper.…”

Section: Introductionsupporting

confidence: 54%

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Teraki

Asano

2019

ApJ

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In high-energy astronomical phenomena, the stochastic particle acceleration by turbulences is one of the promising processes to generate non-thermal particles. In this paper, we investigate the energydiffusion efficiency of relativistic particles in a temporally evolving wave ensemble that consists of a single mode (Alfvén, fast or slow) of linear magnetohydrodynamic waves. In addition to the gyroresonance with waves, the transit-time damping (TTD) also contributes to the energy-diffusion for fast and slow-mode waves. While the resonance condition with the TTD has been considered to be fulfilled by a very small fraction of particles, our simulations show that a significant fraction of particles are in the TTD resonance owing to the resonance broadening by the mirror force, which non-resonantly diffuses the pitch angle of particles. When the cutoff scale in the turbulence spectrum is smaller than the Larmor radius of a particle, the gyroresonance is the main acceleration mechanism for all the three wave modes. For the fast-mode, the coexistence of the gyroresonance and TTD resonance leads to anomalous energy-diffusion. For a particle with its Larmor radius smaller than the cutoff scale, the gyroresonance is negligible, and the TTD becomes the dominant mechanism to diffuse its energy. The energy-diffusion by the TTD-only resonance with fast-mode waves agrees with the hard-sphere-like acceleration suggested in some high-energy astronomical phenomena.

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Section: Introductionsupporting

confidence: 54%

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Teraki

Asano

2019

ApJ

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“…We evaluate E CR,scat numerically for the parameters appropriate to our galaxy sample in Table 1. We find that in starburst galaxies the minimum energies for efficient scattering are of order hundreds of TeV, so scattering by externally-driven turbulence in the ISM is unimportant for nearly all CRs Xu & Lazarian 2018).…”

Section: Turbulent Cascades and Cosmic Ray Scatteringmentioning

confidence: 80%

Cosmic ray transport in starburst galaxies

Krumholz

Crocker

Xu³

et al. 2020

Monthly Notices of the Royal Astronomical Society

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137

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Starburst galaxies are efficient γ-ray producers, because their high supernova rates generate copious cosmic ray (CR) protons, and their high gas densities act as thick targets off which these protons can produce neutral pions and thence γ-rays. In this paper we present a first-principles calculation of the mechanisms by which CRs propagate through such environments, combining astrochemical models with analysis of turbulence in weakly ionised plasma. We show that CRs cannot scatter off the strong large-scale turbulence found in starbursts, because efficient ion-neutral damping prevents such turbulence from cascading down to the scales of CR gyroradii. Instead, CRs stream along field lines at a rate determined by the competition between streaming instability and ion-neutral damping, leading to transport via a process of field line random walk. This results in an effective diffusion coefficient that is nearly energyindependent up to CR energies of ∼ 1 TeV. We apply our computed diffusion coefficient to a simple model of CR escape and loss, and show that the resulting γ-ray spectra are in good agreement with the observed spectra of the starbursts NGC 253, M82, and Arp 220. In particular, our model reproduces these galaxies' relatively hard GeV γ-ray spectra and softer TeV spectra without the need for any fine-tuning of advective escape times or the shape of the CR injection spectrum.

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“…Precise microscopic modeling of the magnetic fluctuation spectra which are produced by both the power of the cluster formation and the different plasma instabilities during the cluster relaxation is non feasible now because it involves the very broad dynamical range of the fluctuations. Physics of the MHD waves in the hot cluster plasmas with high β = 8πnk B (T e + T i )/B 2 (where n is particle number density, electron and ion temperatures are T e and T i and B is magnetic field) is a subject of the current interest (Wiener et al, 2018;Xu and Lazarian, 2018).…”

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confidence: 99%

Shocks and Non-thermal Particles in Clusters of Galaxies

et al. 2019

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Galaxy clusters grow by gas accretion, mostly from mergers of substructures, which release powerful shock waves into cosmic plasmas and convert a fraction of kinetic energy into thermal energy, amplification of magnetic fields and into the acceleration of energetic particles. The modeling of the radio signature of cosmic shocks, combined with the lack of detected γ-rays from cosmic ray (CR) protons, poses challenges to our understanding of how cosmic rays get accelerated and stored in the intracluster medium. Here we review the injection of CRs by cosmic shocks of different strengths, combining the detailed "microscopic" view of collisionless processes governing the creation of non-thermal distributions of electrons and protons in cluster shocks (based on analytic theory and particle-in-cell simulations), with the "macroscopic" view of the large-scale distribution of cosmic rays, suggested by modern cosmological simulations. Time dependent non-linear kinetic models of particle acceleration by multiple internal shocks with large scale compressible motions of plasma with soft CR spectra containing a noticable energy density in the superthermal protons of energies below a few GeV which is difficult to constrain by Fermi

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Resonance-broadened Transit Time Damping of Particles in MHD Turbulence

Cited by 47 publications

References 43 publications

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Cosmic ray transport in starburst galaxies

Shocks and Non-thermal Particles in Clusters of Galaxies

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