A Stringent Limit on the Amplitude of Alfvénic Perturbations in High-Beta Low-Collisionality Plasmas

Squire, Jonathan; Quataert, Eliot; Schekochihin, A. A.

doi:10.3847/2041-8205/830/2/l25

Cited by 47 publications

(116 citation statements)

References 47 publications

Supporting

Mentioning

108

Contrasting

Order By: Relevance

“…Of these stages, (iii) is notably different from the predictions of one-dimensional Landau-fluid (LF) models [9,10]. Figure 2 shows one-dimensional (y-averaged) wave profiles.…”

mentioning

confidence: 91%

“…If these (now stable) fluctuations scatter particles sufficiently strongly, δB z can decay with Δp ≈ −B 2 =4π; if they do not (e.g., if they are resonantly damped [16,29,33]), δB z cannot decrease [9]. The firehose modes' evolution is governed by Δp [12], which varies in space.…”

mentioning

confidence: 99%

“…We initialize with λ A ¼ L x in the out-of-plane field, δB z ¼ −δbB 0 cosð2πx=λ A Þ, and, for the traveling wave, a corresponding velocity perturbation, δu z ¼ δbv A cosð2πx=λ A Þ. In each case, we take the wave amplitude δb ¼ 0.5, which is well above the interruption limit δb max ≈ 2β −1=2 [9]. Within the MHD model, these initial conditions would create continuing sinusoidal SA oscil-…”

mentioning

confidence: 99%

See 2 more Smart Citations

Kinetic Simulations of the Interruption of Large-Amplitude Shear-Alfvén Waves in a High- β Plasma

et al. 2017

Self Cite

View full text Add to dashboard Cite

Using two-dimensional hybrid-kinetic simulations, we explore the nonlinear "interruption" of standing and traveling shear-Alfvén waves in collisionless plasmas. Interruption involves a self-generated pressure anisotropy removing the restoring force of a linearly polarized Alfvénic perturbation, and occurs for wave amplitudes δB ⊥ =B 0 ≳ β −1=2 (where β is the ratio of thermal to magnetic pressure). We use highly elongated domains to obtain maximal scale separation between the wave and the ion gyroscale. For standing waves above the amplitude limit, we find that the large-scale magnetic field of the wave decays rapidly. The dynamics are strongly affected by the excitation of oblique firehose modes, which transition into long-lived parallel fluctuations at the ion gyroscale and cause significant particle scattering. Traveling waves are damped more slowly, but are also influenced by small-scale parallel fluctuations created by the decay of firehose modes. Our results demonstrate that collisionless plasmas cannot support linearly polarized Alfvén waves above δB ⊥ =B 0 ∼ β −1=2 . They also provide a vivid illustration of two key aspects of low-collisionality plasma dynamics: (i) the importance of velocity-space instabilities in regulating plasma dynamics at high β, and (ii) how nonlinear collisionless processes can transfer mechanical energy directly from the largest scales into thermal energy and microscale fluctuations, without the need for a scale-by-scale turbulent cascade.

show abstract

“…Of these stages, (iii) is notably different from the predictions of one-dimensional Landau-fluid (LF) models [9,10]. Figure 2 shows one-dimensional (y-averaged) wave profiles.…”

mentioning

confidence: 91%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Kinetic Simulations of the Interruption of Large-Amplitude Shear-Alfvén Waves in a High- β Plasma

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…In fact, it is almost certain that MHD and plasma process play a key role in the underlying transport processes (Squire et al 2016;Kunz et al 2015), and that these processes may be determined on scales as small as the proton gyro-radius, which for typical Virgo ICM parameters would be many orders of magnitude below the spatial scales we are probing here. However, whatever these underlying processes are, the ICM apparently behaves as an inviscid fluid on macroscopic scales.…”

Section: Discussionmentioning

confidence: 99%

Stripped Elliptical Galaxies as Probes of ICM Physics. III. Deep Chandra Observations of NGC 4552: Measuring the Viscosity of the Intracluster Medium

Kraft

Röediger

Macháček

et al. 2017

ApJ

View full text Add to dashboard Cite

We present results from a deep (200 ks) Chandra observation of the early-type galaxy NGC 4552 (M89) which is falling into the Virgo cluster. Previous shallower X-ray observations of this galaxy showed a remnant gas core, a tail to the South of the galaxy, and twin 'horns' attached to the northern edge of the gas core (Machacek et al. 2005a). In our deeper data, we detect a diffuse, low surface brightness extension to the previously known tail, and measure the temperature structure within the tail. We combine the deep Chandra data with archival XMM-Newton observations to put a strong upper limit on the diffuse emission of the tail out to a large distance (10×the radius of the remnant core) from the galaxy center. In our two previous papers (Roediger et al. 2015a,b), we presented the results of hydrodynamical simulations of ram pressure stripping specifically for M89 falling into the Virgo cluster and investigated the effect of ICM viscosity. In this paper, we compare our deep data with our specifically tailored simulations and conclude that the observed morphology of the stripped tail in NGC 4552 is most similar to the inviscid models. We conclude that, to the extent the transport processes can be simply modeled as a hydrodynamic viscosity, the ICM viscosity is negligible. More generally, any micro-scale description of the transport processes in the high-β plasma of the cluster ICM must be consistent with the efficient mixing observed in the stripped tail on macroscopic scales.

show abstract

“…The division of turbulence into these two regimes is convenient, but the coupling between the two can be highly nontrivial. For example, in high-beta plasmas, kinetic effects can build up a pressure anisotropy that destabilizes largescale, high-amplitude shear Alfvén waves to the firehose instability, conceivably causing a direct transfer of energy from large scales to kinetic scales, bypassing the turbulent cascade (Squire et al 2016(Squire et al , 2017. In a similar vein, in low-beta plasmas with dynamic alignment, the inertial-range energy cascade may be mediated by the collisionless tearing instability at small scales, rather than classical nonlinear eddy interactions.…”

Section: Turbulence Preliminariesmentioning

confidence: 99%

Numerical investigation of kinetic turbulence in relativistic pair plasmas – I. Turbulence statistics

Zhdankin

Uzdensky

Werner

et al. 2017

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We describe results from particle-in-cell simulations of driven turbulence in collisionless, magnetized, relativistic pair plasma. This physical regime provides a simple setting for investigating the basic properties of kinetic turbulence and is relevant for high-energy astrophysical systems such as pulsar wind nebulae and astrophysical jets. In this paper, we investigate the statistics of turbulent fluctuations in simulations on lattices of up to 1024 3 cells and containing up to 2 × 10 11 particles. Due to the absence of a cooling mechanism in our simulations, turbulent energy dissipation reduces the magnetization parameter to order unity within a few dynamical times, causing turbulent motions to become sub-relativistic. In the developed stage, our results agree with predictions from magnetohydrodynamic turbulence phenomenology at inertial-range scales, including a power-law magnetic energy spectrum with index near −5/3, scaledependent anisotropy of fluctuations described by critical balance, log-normal distributions for particle density and internal energy density (related by a 4/3 adiabatic index, as predicted for an ultra-relativistic ideal gas), and the presence of intermittency. We also present possible signatures of a kinetic cascade by measuring power-law spectra for the magnetic, electric, and density fluctuations at sub-Larmor scales.

show abstract

A Stringent Limit on the Amplitude of Alfvénic Perturbations in High-Beta Low-Collisionality Plasmas

Cited by 47 publications

References 47 publications

Kinetic Simulations of the Interruption of Large-Amplitude Shear-Alfvén Waves in a High- β Plasma

Kinetic Simulations of the Interruption of Large-Amplitude Shear-Alfvén Waves in a High- β Plasma

Stripped Elliptical Galaxies as Probes of ICM Physics. III. Deep Chandra Observations of NGC 4552: Measuring the Viscosity of the Intracluster Medium

Numerical investigation of kinetic turbulence in relativistic pair plasmas – I. Turbulence statistics

Contact Info

Product

Resources

About