Ion temperature gradient driven turbulence with strong trapped ion resonance

Kosuga, Y.; Itoh, Sanae I.; Diamond, P. H.; Itoh, K.; Lesur, Maxime

doi:10.1063/1.4897179

Cited by 15 publications

(11 citation statements)

References 45 publications

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“…Following the previous work, 9,14,15,33,34 we can construct the two-point correlation evolution Following the standard procedure of symmetrization with respect to the two points and ensemble averaging, 35 we obtain…”

Section: Two-point Decorrelation Analysesmentioning

confidence: 99%

Anisotropic E × B shearing rate in a magnetic island

et al. 2021

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We derive the ExB shearing rate associated with vortex flow inside a macroscopic magnetic island (MI) in axisymmetric toroidal geometry. Due to the elongation of the MI and incompressibility of the ExB flow, the shearing rate near X-points is much lower than that near the mid-plane (x-axis of the local Cartesian coordinate) of the MI on the same flux surface. Furthermore, the rate formally vanishes at the X-points where the local poloidal magnetic field associated with the MI stagnates. This calculation of ExB shearing profile and, in particular minimal ExB shear near the X-points is consistent with the recent experimental finding that turbulence tends to spread into an MI through regions around the X-points [K. Ida et al., Phys. Rev. Lett. 120, 245001 (2018)], and can contribute to more thorough quantitative interpretation of the results from experiments and simulations.

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Section: Two-point Decorrelation Analysesmentioning

confidence: 99%

Anisotropic E × B shearing rate in a magnetic island

et al. 2021

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“…Fast-forwarding over several decades of plasma-turbulence theory (see Krommes 2015 and Laval, Pesme & Adam 2016 for review and references), the notion of ‘phase-space turbulence’, pioneered by Dupree (1972), has, in the recent years, again become a popular object of study, treated either, Dupree-style, in terms of formation of phase-space structures and their effect on the transport properties of the plasma (Kosuga & Diamond 2011; Lesur, Diamond & Kosuga 2014 a , b ; Kosuga et al. 2014, 2017) or in terms of a kinetic cascade carrying free energy to collisional scales in velocity space (Watanabe & Sugama 2004; Schekochihin et al. 2008, 2009; Tatsuno et al.…”

Section: Introductionmentioning

confidence: 99%

“…It has long been realised that nonlinear effects can lead to Landau damping shutting down, both for broad-spectrum fields and individual monochromatic waves (Vedenov, Velikhov & Sagdeev 1962;Mazitov 1965;O'Neil 1965;Manheimer & Dupree 1968;Weiland 1992), or even to apparently damped perturbations coming back from phase space, a phenomenon called 'plasma echo' (Gould, O'Neil & Malmberg 1967;Malmberg et al 1968). Fast-forwarding over several decades of plasma-turbulence theory (see Krommes 2015 and Laval, Pesme & Adam 2016 for review and references), the notion of 'phase-space turbulence', pioneered by Dupree (1972), has, in the recent years, again become a popular object of study, treated either, Dupree-style, in terms of formation of phase-space structures and their effect on the transport properties of the plasma (Kosuga & Diamond 2011;Lesur, Diamond & Kosuga 2014a,b;Kosuga et al 2014Kosuga et al , 2017 or in terms of a kinetic cascade carrying free energy to collisional scales in velocity space (Watanabe & Sugama 2004;Schekochihin et al 2008Tatsuno et al 2009;Plunk et al 2010;Bañón Navarro et al 2011;Plunk & Tatsuno 2011;Teaca et al 2012Teaca et al , 2016Hatch et al 2014;Kanekar 2015;Parker et al 2016;Schekochihin et al 2016;Servidio et al 2017).…”

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confidence: 99%

A solvable model of Vlasov-kinetic plasma turbulence in Fourier–Hermite phase space

Adkins

Schekochihin

2018

J. Plasma Phys.

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A class of simple kinetic systems is considered, described by the 1D Vlasov-Landau equation with Poisson or Boltzmann electrostatic response and an energy source. Assuming a stochastic electric field, a solvable model is constructed for the phase-space turbulence of the particle distribution. The model is a kinetic analog of the Kraichnan-Batchelor model of chaotic advection. The solution of the model is found in Fourier-Hermite space and shows that the free-energy flux from low to high Hermite moments is suppressed, with phase mixing cancelled on average by anti-phase-mixing (stochastic plasma echo). This implies that Landau damping is an ineffective route to dissipation (i.e., to thermalisation of electric energy via velocity space). The full Fourier-Hermite spectrum is derived. Its asymptotics are m −3/2 at low wave numbers and high Hermite moments (m) and m −1/2 k −2 at low Hermite moments and high wave numbers (k). These conclusions hold at wave numbers below a certain cut off (analog of Kolmogorov scale), which increases with the amplitude of the stochastic electric field and scales as inverse square of the collision rate. The energy distribution and flows in phase space are a simple and, therefore, useful example of competition between phase mixing and nonlinear dynamics in kinetic turbulence, reminiscent of more realistic but more complicated multi-dimensional systems that have not so far been amenable to complete analytical solution.

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“…Similarly to the 1D systems discussed above, the mechanism is based on the nonlinear growth of a hole structure in phase-space [61,74]. The mechanism still works in the present of turbulent decorrelation of such structures [75,76] so this is relevant to the context of granulation [77].…”

Section: Overviewmentioning

confidence: 99%

Subcritical Instabilities in Neutral Fluids and Plasmas

Lesur

Médina

Sasaki

et al. 2018

Fluids

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In neutral fluids and plasmas, the analysis of perturbations often starts with an inventory of linearly unstable modes. Then, the nonlinear steady-state is analyzed or predicted based on these linear modes. A crude analogy would be to base the study of a chair on how it responds to infinitesimaly small perturbations. One would conclude that the chair is stable at all frequencies, and cannot fall down. Of course, a chair falls down if subjected to finite-amplitude perturbations. Similarly, waves and wave-like structures in neutral fluids and plasmas can be triggered even though they are linearly stable. These subcritical instabilities are dormant until an interaction, a drive, a forcing, or random noise pushes their amplitude above some threshold. Investigating their onset conditions requires nonlinear calculations. Subcritical instabilities are ubiquitous in neutral fluids and plasmas. In plasmas, subcritical instabilities have been investigated based on analytical models and numerical simulations since the 1960s. More recently, they have been measured in laboratory and space plasmas, albeit not always directly. The topic could benefit from the much longer and richer history of subcritical instability and transition to subcritical turbulence in neutral fluids. In this tutorial introduction, we describe the fundamental aspects of subcritical instabilities in plasmas, based on systems of increasing complexity, from simple examples of a point-mass in a potential well or a box on a table, to turbulence and instabilities in neutral fluids, and finally, to modern applications in magnetized toroidal fusion plasmas.

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Ion temperature gradient driven turbulence with strong trapped ion resonance

Cited by 15 publications

References 45 publications

Anisotropic E × B shearing rate in a magnetic island

Anisotropic E × B shearing rate in a magnetic island

A solvable model of Vlasov-kinetic plasma turbulence in Fourier–Hermite phase space

Subcritical Instabilities in Neutral Fluids and Plasmas

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