Particle Acceleration in Superluminal Strong Waves

Teraki, Yuto; Ito, Hirotaka; Nagataki, Shigehiro

doi:10.1088/0004-637x/805/2/138

Cited by 4 publications

(3 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spectrum of transmitted electrons resembles a relativistic Maxwellian, M (γ) ∝ γ γ 2 − 1 exp(−γ/∆γ), shown, for comparison as a black dotted line. This is in agreement with the results of Sironi & Spitkovsky (2011) and Teraki et al (2015), who studied acceleration in the driven magnetic reconnection and in the superluminal regimes, respectively. The peak energy of the distribution is Γ s (σ + 1), shown in Fig.…”

Section: Test-particle Trajectoriessupporting

confidence: 92%

Electron Acceleration at Pulsar Wind Termination Shocks

Giacchè

Kirk

2017

ApJ

View full text Add to dashboard Cite

We study the acceleration of electrons and positrons at an electromagnetically modified, ultrarelativistic shock in the context of pulsar wind nebulae (PWNe). We simulate the outflow produced by an obliquely rotating pulsar in proximity of its termination shock with a two-fluid code which uses a magnetic shear wave to mimic the properties of the wind. We integrate electron trajectories in the test-particle limit in the resulting background electromagnetic fields to analyse the injection mechanism. We find that the shock-precursor structure energizes and reflects a sizeable fraction of particles, which becomes available for further acceleration. We investigate the subsequent first-order Fermi process sustained by small-scale magnetic fluctuations with a Monte Carlo code. We find that the acceleration proceeds in two distinct regimes: when the gyro-radius r g exceeds the wavelength of the shear λ, the process is remarkably similar to first-order Fermi acceleration at relativistic, parallel shocks. This regime corresponds to a low density wind which allows the propagation of superluminal waves. When r g < λ, which corresponds to the scenario of driven reconnection, the spectrum is softer.

show abstract

Section: Test-particle Trajectoriessupporting

confidence: 92%

Electron Acceleration at Pulsar Wind Termination Shocks

Giacchè

Kirk

2017

ApJ

View full text Add to dashboard Cite

show abstract

“…Applicability of the analytic models to the strong turbulence has been investigated using test particle simulations, but it is still controversial. The turbulence is usually provided by a superposition of plane waves in the Fourier space (e.g., O'Sullivan et al 2009;Fatuzzo & Melia 2014;Teraki et al 2015), or driven by some algorithms (e.g., Dmitruk et al 2003;Teaca et al 2014;Lynn et al 2014). These studies are useful to investigate features of the stochastic acceleration owing to their controllablity of the turbulence.…”

Section: Introductionmentioning

confidence: 99%

Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows

Kimura

Tomida

Murase

2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We investigate acceleration and propagation processes of high-energy particles inside hot accretion flows. The magnetorotational instability (MRI) creates turbulence inside accretion flows, which triggers magnetic reconnection and may produce non-thermal particles. They can be further accelerated stochastically by the turbulence. To probe the properties of such relativistic particles, we perform magnetohydrodynamic simulations to obtain the turbulent fields generated by the MRI, and calculate orbits of the high-energy particles using snapshot data of the MRI turbulence. We find that the particle acceleration is described by a diffusion phenomenon in energy space with a diffusion coefficient of the hard-sphere type: D ǫ ∝ ǫ 2 , where ǫ is the particle energy. Eddies in the largest scale of the turbulence play a dominant role in the acceleration process. On the other hand, the stochastic behaviour in configuration space is not usual diffusion but superdiffusion: the radial displacement increases with time faster than that in the normal diffusion. Also, the magnetic field configuration in the hot accretion flow creates outward bulk motion of high-energy particles. This bulk motion is more effective than the diffusive motion for higher energy particles. Our results imply that typical active galactic nuclei that host hot accretion flows can accelerate CRs up to ǫ ∼ 0.1 − 10 PeV.

show abstract

“…To establish the picture of the energy-diffusion process from a fundamental point, we neglect the nonlinear wave-wave interaction and anisotropy of the turbulence. This method has been widely used for the investigation of the spatial diffusion (Sun & Jokipii 2011, 2015Hussein et al 2015); radiation spectra from the charged particles moving in the turbulence (Teraki & Takahara 2011, 2014; and the diffusion in the momentum space (O'sullivan et al 2009;Teraki et al 2015). With this method, we can focus on each wave mode without additional effects such as boundary effect or wave damping.…”

Section: Introductionmentioning

confidence: 99%

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Teraki

Asano

2019

ApJ

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Particle Acceleration in Superluminal Strong Waves

Cited by 4 publications

References 35 publications

Electron Acceleration at Pulsar Wind Termination Shocks

Electron Acceleration at Pulsar Wind Termination Shocks

Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows

Particle Energy Diffusion in Linear Magnetohydrodynamic Waves

Contact Info

Product

Resources

About