The predictions of gyrokinetic and gyrofluid simulations ion-temperature-gradient (ITG) instability turbulence in tokamak plasmas as well some plasma thermal transport models, which have been widely used for predicting the performance proposed International Thermonuclear Experimental Reactor (ITER) [Plasma Physics Controlled Nuclear Fusion Research, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 1, p. 3], are compared. These comparisons provide information on effects...

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations the solar wind, interstellar medium galaxy clusters, as well models particle heating accretion disks. All these plasmas many others have turbulent motions at weakly collisional collisionless scales. The focuses on strong mean magnetic field. key assumptions are that small compared to field, spatially anisotropic...

A closed set of fluid moment equations is developed which represents kinetic Landau damping physics and takes a simple form in wave-number space. The linear-response function corresponds to three-pole (or four-pole) approximation the plasma dispersion Z. Alternatively, response exact for distribution close Maxwellian, but decreases asymptotically as 1/${\mathit{v}}^{4}$ 1/${\mathit{v}}^{6}$). Among other applications, these should be useful nonlinear studies turbulence driven by...

A physically comprehensive and theoretically based transport model tuned to three-dimensional (3-D) ballooning mode gyrokinetic instabilities gyrofluid nonlinear turbulence simulations is formulated with global local magnetic shear stabilization E×B rotational stabilization. Taking no fit coefficients from experiment, the tested against a large profile database good agreement. This capable of describing enhanced core confinement barriers in negative central discharges on The used make...

Deuterium neutral beams with energies up to 110 keV were injected into TFTR (Tokamak Fusion Test Reactor) plasmas at low magnetic field such that the beam injection velocities comparable Alfv\'en velocity. Excitation of toroidal eigenmodes was observed by Mirnov coils and emission spectroscopy.

This paper studies the turbulent cascade of magnetic energy in weakly collisional magnetized plasmas. A model is presented, based on assumptions local nonlinear transfer wavenumber space, critical balance between linear propagation and interaction times, applicability dissipation rates for nonlinearly plasma. The follows from driving scale MHD regime, through transition at ion Larmor radius into kinetic Alfven wave which turbulence dissipated by processes. fluctuations remain frequencies...

This Letter presents the first ab initio, fully electromagnetic, kinetic simulations of magnetized turbulence in a homogeneous, weakly collisional plasma at scale ion Larmor radius (ion gyroscale). Magnetic- and electric-field energy spectra show break gyroscale; spectral slopes are consistent with scaling predictions for critically balanced Alfvén waves above gyroscale (spectral index -5/3) below indices -7/3 magnetic -1/3 electric fluctuations). behavior is also qualitatively situ...

Turbulence in tokamaks is characterized by long parallel wavelengths and short perpendicular wavelengths. A coordinate system for nonlinear fluid, gyrokinetic ‘‘Vlasov,’’ or particle simulations presented that exploits the elongated nature of turbulence resolving minimum necessary simulation volume: a thin twisting flux tube. It very similar to ballooning representation, although periodicity constraints can be incorporated manner allows E×B nonlinearities evaluated efficiently with fast...

A first-principles model of anomalous thermal transport based on numerical simulations is presented, with stringent comparisons to experimental data from the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. This nonlinear gyrofluid simulations, which predict fluctuation and characteristics toroidal ion-temperature-gradient-driven (ITG) turbulence, comprehensive linear gyrokinetic ballooning calculations, provide very accurate growth rates, critical temperature gradients,...

Nonlinear gyrofluid equations are derived by taking moments of the nonlinear, electrostatic gyrokinetic equation. The principal model presented includes evolution for guiding center n, u∥, T∥, and T⊥ along with an equation expressing quasineutrality constraint. Additional higher that may be used if greater accuracy is desired. moment hierarchy closed a Landau damping [G. W. Hammett F. Perkins, Phys. Rev. Lett. 64, 3019 (1990)], which equivalent to multipole approximation plasma dispersion...

Under certain conditions, the electron heat transport induced by temperature gradient (ETG) streamers is sufficiently large and sensitive with respect to normalized represent a possible cause for profile consistency (“stiffness”). Here, linear gyrokinetic simulations of toroidal ETG modes in tokamak core edge plasmas are presented. An algebraic formula threshold instability derived from numerical solutions equations which recovers previous analytical results appropriate limits.

A status report is given on developments in the gyrofluid approach to simulating tokamak turbulence. 'Gyrofluid' (r 'gyro-Landau fluid') equations attempt extend range of validity fluid a more collisionless regime typical tokamaks, by developing models important kinetic effects such as Landau-damping and gyro-orbit averaging. The moments should converge if enough are kept, though this may require large number for some processes. Toroidal have been extended from 4 6 moments, include mu Del B...

Theory of E×B shear suppression turbulence in toroidal geometry [Phys. Plasmas 2, 1648 (1995)] is extended to include fast time variations the flows often observed nonlinear simulations tokamak turbulence. It shown that quickly varying components flows, while they typically contribute significantly instantaneous shearing rate, are less effective than slowly suppressing This because flow pattern changes before eddies get distorted enough. The rate capturing this important physics analytically...

Magnetohydrodynamic (MHD) turbulence is encountered in a wide variety of astrophysical plasmas, including accretion disks, the solar wind, and interstellar intracluster medium. On small scales, this often expected to consist highly anisotropic fluctuations with frequencies compared ion cyclotron frequency. For number applications, scales are also collisionless, so kinetic treatment necessary. We show that well described by low frequency expansion theory called gyrokinetics. This paper first...

A closed set of fluid moment equations including models kinetic Landau damping is developed which describes the evolution collisionless plasmas in magnetohydrodynamic parameter regime. The model fully electromagnetic and dynamics both compressional shear Alfvén waves, as well ion acoustic waves. allows for separate parallel perpendicular pressures p∥ p⊥, and, unlike previous such Chew–Goldberger–Low theory, correctly predicts instability threshold mirror instability. Both a simple 3+1 more...

The gyro-Landau fluid (GLF) model equations for toroidal geometry [R. E. Waltz, R. Dominguez, and G. W. Hammett, Phys. Fluids B 4, 3138 (1992)] have been recently applied to study ion temperature gradient (ITG) mode turbulence using the three-dimensional (3-D) nonlinear ballooning representation (BMR) outlined earlier D. Kerbel, J. Milovich, Plasmas 1, 2229 (1994)]. present paper extends this work by treating some unresolved issues concerning ITG with adiabatic electrons. Although eddies are...

We show that under very general conditions, cluster plasmas threaded by weak magnetic fields are subject to fast growing plasma instabilities driven the anisotropy of pressure (viscous stress) with respect local direction field. Such an will naturally arise in any weakly magnetized has low collisionality and is stirring. The field must be sufficiently for occur, viz., beta>Re^{1/2}. captured extended MHD model Braginskii viscosity. However, their growth rates proportional wavenumber down...

Turbulent fluctuations in plasmas with reversed magnetic shear have been investigated on the Tokamak Fusion Test Reactor. Under intense auxiliary heating, these are observed to bifurcate into two states different transport properties. In state better confinement, it has found that level of is very small throughout most region negative shear. By contrast, lower confinement characterized by large bursts which suggest a competition between driving and suppression turbulence. These results...

A set of nonlinear gyrofluid equations for simulations tokamak turbulence are derived by taking moments the toroidal gyrokinetic equation. The moment hierarchy is closed with approximations that model kinetic effects parallel Landau damping, drift resonances, and finite Larmor radius effects. These generalize work Dorland Hammett [Phys. Fluids B 5, 812 (1993)] to geometry including essential closures phase mixing from ∇B curvature drifts take basic form presented in Waltz et al. 4, 3138...

We describe local shearing box simulations of turbulence driven by the magnetorotational instability (MRI) in a collisionless plasma. Collisionless effects may be important radiatively inefficient accretion flows, such as near black hole Galactic Center. The MHD version ZEUS is modified to evolve an anisotropic pressure tensor. A fluid closure approximation used calculate heat conduction along magnetic field lines. tensor provides qualitatively new mechanism for transporting angular momentum...

This Letter presents nonlinear gyrokinetic simulations of microtearing mode turbulence. The include collisional and electromagnetic effects use experimental parameters from a high-β discharge in the National Spherical Torus Experiment. predicted electron thermal transport is comparable to that given by analysis, it dominated contribution electrons free-streaming along resulting stochastic magnetic field line trajectories. Experimental values flow shear can significantly reduce transport.

A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., ITG turbulence) is proposed, with account taken both the nonlinear advection perturbed particle distribution by fluctuating ExB flows and its phase mixing, which caused streaming particles along mean magnetic field and, linear problem, would lead to Landau damping. It found that it possible construct consistent very little free energy leaks into high velocity moments function,...

Nonlinear energy transfer and dissipation in Alfvén wave turbulence are analyzed the first gyrokinetic simulation spanning all scales from tail of MHD range to electron gyroradius scale. For typical solar wind parameters at 1 AU, about 30% nonlinear close scale is mediated by modes cascade. Collisional occurs across entire kinetic k(⊥)ρ(I)≳1. Both mechanisms thus act on multiple coupled scales, which have be retained for a comprehensive picture Alfvénic turbulence.

Fluidlike models have long been used to develop qualitative understanding of the drift-wave class instabilities (such as ion temperature gradient mode and various trapped-particle modes) which are prime candidates for explaining anomalous transport in plasmas. Here, fluid approach is improved by developing fairly realistic kinetic effects, such Landau damping gyroradius orbit averaging, strongly affect both linear properties resulting nonlinear turbulence. Central this work a simple but...