Stratified Simulations of Collisionless Accretion Disks

Hirabayashi, Kota; Hoshino, Masahiro

doi:10.3847/1538-4357/aa74b3

Cited by 7 publications

(5 citation statements)

References 35 publications

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“…Resistivity creates an electric field parallel to a magnetic field in a dissipation scale, which might affect the energy of CRs. The features of the MRI turbulence can be affected by the anisotropic pressure (Quataert et al 2002;Sharma et al 2006;Kunz et al 2014;Hirabayashi & Hoshino 2017) and/or anisotropic heat transfer (Ressler et al 2015;Foucart et al 2017). Magnetic reconnections are expected to have some influence on the MRI turbulence, since they are important dissipation processes (e.g., Sano & Inutsuka 2001).…”

Section: Future Directionsmentioning

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

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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.

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Section: Future Directionsmentioning

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

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“…The nonlinear effect associated with the deviation from the unperturbed distribution function does not seem to be included appropriately. Indeed, a typical strategy for nonlinear collisionless MHD simulations 6,19,20 is to include artificial pitch-angle scatterings, which will be turned on if the anisotropy develops into unstable regimes because otherwise, there is nothing to suppress the kinetic instability.…”

Section: Discussionmentioning

confidence: 99%

“…Note that, as we can see from Eqs. (20)(21), this introduces extra terms into the equations for pxz , pyz . With the same closure (p 0 now replaces p 0 ), we have the following dispersion relation:…”

Section: Closure In Wavenumber Spacementioning

confidence: 99%

A non-local fluid closure for modeling cyclotron resonance in collisionless magnetized plasmas

Jikei,

Amano

2021

Preprint

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A fluid description for collisionless magnetized plasmas that takes into account the effect of cyclotron resonance has been developed. Following the same approach as the Landau fluid closure, the heat flux components associated with transverse electromagnetic fluctuations are approximated by a linear combination of lower-order moments in wavenumber space. The closure successfully reproduces the linear cyclotron resonance for electromagnetic waves propagating parallel to the ambient magnetic field. In the presence of finite temperature anisotropy, the model gives approximately correct prediction for an instability destabilized via the cyclotron resonance. A nonlinear simulation demonstrates the wave growth consistent with the linear theory followed by the reduction of initial anisotropy, and finally, the saturation of the instability. The isotropization may be understood in terms of quasi-linear theory, which is developed within the framework of the fluid model but very similar to its fully kinetic counterpart. The result indicates that both linear and nonlinear collisionless plasma responses are approximately incorporated in the fluid model.

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“…In all these simulations no shock has been found comparing with reflected and injected jet simulations. More advanced kinetic instabilities are found in magnetorotational instability (MRI) (e.g., Hoshino 2015;Kunz et al 2016;Hirabayashi and Hoshino 2017;Kimura et al 2019). Hirabayashi and Hoshino (2017) show a series of stratified-shearing-box simulations of collisionless accretion disks in the recently developed framework of kinetic MHD, which can handle finite non-gyrotropy of a pressure tensor.…”

Section: Weibel Instabilities With Various Flavoursmentioning

confidence: 99%

“…More advanced kinetic instabilities are found in magnetorotational instability (MRI) (e.g., Hoshino 2015;Kunz et al 2016;Hirabayashi and Hoshino 2017;Kimura et al 2019). Hirabayashi and Hoshino (2017) show a series of stratified-shearing-box simulations of collisionless accretion disks in the recently developed framework of kinetic MHD, which can handle finite non-gyrotropy of a pressure tensor. Although a fully kinetic simulation predicted a more efficient angular-momentum transport in collisionless disks than in the standard MHD regime, the enhanced transport has not been observed in past kinetic-MHD approaches to gyrotropic pressure anisotropy.…”

Section: Weibel Instabilities With Various Flavoursmentioning

confidence: 99%

PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

Nishikawa¹,

Duţan

Köhn

et al. 2021

Living Rev Comput Astrophys

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The Particle-In-Cell (PIC) method has been developed by Oscar Buneman, Charles Birdsall, Roger W. Hockney, and John Dawson in the 1950s and, with the advances of computing power, has been further developed for several fields such as astrophysical, magnetospheric as well as solar plasmas and recently also for atmospheric and laser-plasma physics. Currently more than 15 semi-public PIC codes are available which we discuss in this review. Its applications have grown extensively with increasing computing power available on high performance computing facilities around the world. These systems allow the study of various topics of astrophysical plasmas, such as magnetic reconnection, pulsars and black hole magnetosphere, non-relativistic and relativistic shocks, relativistic jets, and laser-plasma physics. We review a plethora of astrophysical phenomena such as relativistic jets, instabilities, magnetic reconnection, pulsars, as well as PIC simulations of laser-plasma physics (until 2021) emphasizing the physics involved in the simulations. Finally, we give an outlook of the future simulations of jets associated to neutron stars, black holes and their merging and discuss the future of PIC simulations in the light of petascale and exascale computing.

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Stratified Simulations of Collisionless Accretion Disks

Cited by 7 publications

References 35 publications

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

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

A non-local fluid closure for modeling cyclotron resonance in collisionless magnetized plasmas

PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

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