Collisionless electron-temperature-gradient-driven (ETG) turbulence in toroidal geometry is studied via nonlinear numerical simulations. To this aim, two massively parallel, fully gyrokinetic Vlasov codes are used, both including electromagnetic effects. Somewhat surprisingly, and unlike the analogous case of ion-temperature-gradient-driven (ITG) turbulence, we find that turbulent electron heat flux significantly underpredicted by simple mixing length estimates a certain parameter regime...

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...

The first toroidal, gyrokinetic, electromagnetic simulations of small scale plasma turbulence are presented. considered is driven by gradients in the electron temperature. It found that temperature gradient (ETG) can induce experimentally relevant thermal losses magnetic confinement fusion devices. For typical tokamak parameters, transport essentially electrostatic character. simulation results qualitatively consistent with a model balances linear and secondary mode growth rates. Significant...

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...

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...

A three-dimensional, nonlinear gyrokinetic simulation of plasma turbulence resolving scales from the ion to electron gyroradius with a realistic mass ratio is presented, where all damping provided by resolved physical mechanisms. The resulting energy spectra are quantitatively consistent magnetic power spectrum scaling k(-2.8) as observed in situ spacecraft measurements "dissipation range" solar wind turbulence. Despite strongly nature turbulence, linear kinetic Alfvén wave mode describes...

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...

We address the mechanisms underlying zonal flow generation and stability in turbulent systems driven by electrostatic ion-temperature-gradient (ITG) mode. In case of stability, we show poloidal flows typical numerical simulations become unstable when they exceed a critical level. Near marginal linear ITG mode, system can generate that are sufficiently weak to remain stable strong suppress This region corresponds parameter regime nonlinear Dimits up-shift.

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...

Differential rotation occurs in conducting flows accretion disks and planetary cores. In such systems, the magnetorotational instability can arise from coupling Lorentz centrifugal forces to cause large radial angular momentum fluxes. We present first experimental observation of instability. Our system consists liquid sodium between differentially rotating spheres, with an imposed coaxial magnetic field. characterize observed patterns, dynamics, torque increases, establish that this occur a...

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...

A new analytically and numerically manageable model collision operator is developed specifically for turbulence simulations. The like-particle includes both pitch-angle scattering energy diffusion satisfies the physical constraints required operators: it conserves particles, momentum, energy, obeys Boltzmann’s H-theorem (collisions cannot decrease entropy), vanishes on a Maxwellian, efficiently dissipates small-scale structure in velocity space. process of transforming this into gyroaveraged...

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,...

Abstract A theoretical model is presented that for the first time matches experimental measurements of pedestal width-height Diallo scaling in low-aspect-ratio high- β tokamak NSTX. Combining linear gyrokinetics with self-consistent equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, shown to limit achievable confinement spherical pedestals. Simulations are used find novel Gyrokinetic Critical Pedestal constraint, which determines steepest pressure...

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...

The confinement improvement in reversed-shear experiments on the Tokamak Fusion Test Reactor [Plasma Phys. Controlled 26, 11 (1984)] is investigated using nonlinear gyrofluid simulations including a bounce-averaged trapped electron fluid model. This model includes important kinetic effects for both ions and electrons, agrees well with linear theory. Both reversed shear Shafranov shift reverse precession drifts of large fraction which significantly reduces growth rate mode, found to be...

Nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence, within an internal particle transport barrier, are performed and compared with experimental data. The results provide a mechanism for barrier control on-axis radio frequency heating, as demonstrated in Alcator C-Mod experiments [S. J. Wukitch et al., Phys. Plasmas 9, 2149 (2002)]. Off-axis heating produces energy after the transition to enhanced Dα high confinement mode. foot reaches half-radius, peak density 2.5...

The experimental conditions under which tokamak turbulence at hyperfine (electron gyroradius) scales is predicted to be significant and observable are described. first quantitative predictions of fluctuation amplitudes, spectral features, the associated electron energy transport presented. A novel theoretical model quantitatively describes boundaries high-amplitude streamer regime presented shown explain gyrokinetic simulation results. This uniquely includes consideration two distinct...

Electrostatic turbulence in weakly collisional, magnetized plasma can be interpreted as a cascade of entropy phase space, which is proposed universal mechanism for dissipation energy turbulence. When the nonlinear decorrelation time at scale thermal Larmor radius shorter than collision time, broad spectrum fluctuations sub-Larmor scales numerically found velocity and position with theoretically predicted scalings. The results are important because they identify what probably Kolmogorov-like...