Multi-dimensional gyrokinetic parameter studies based on eigenvalue computations

Merz, F.; Kowitz, Christoph; Romero, Eloy; Román, José E.; Jenko, F.

doi:10.1016/j.cpc.2011.12.018

Cited by 14 publications

(10 citation statements)

References 23 publications

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“…[8][9][10][11] The results of this study are also expected to provide insights into the nonlinear effect of turbulence which is driven by the unstable linear eigenmodes studied here. Microturbulence and the associated transport in fusion plasmas frequently retain signatures of the underlying linear eigenmode spectra.…”

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confidence: 99%

Aspects of linear Landau damping in discretized systems

et al. 2013

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Discrete kinetic eigenmode spectra of electron plasma oscillations in weakly collisional plasma: A numerical study Phys. Plasmas 20, 012125 (2013) Non-planar ion-acoustic solitary waves and their head-on collision in a plasma with nonthermal electrons and warm adiabatic ions Phys. Plasmas 20, 012122 (2013) The incomplete plasma dispersion function: Properties and application to waves in bounded plasmas Phys. Plasmas 20, 012118 (2013) Effect of ion temperature on ion-acoustic solitary waves in a magnetized plasma in presence of superthermal electrons Phys. Plasmas 20, 012306 (2013) Additional information on Phys. Plasmas Basic linear eigenmode spectra for electrostatic Langmuir waves and drift-kinetic slab ion temperature gradient modes are examined in a series of scenarios. Collisions are modeled via a Lenard-Bernstein collision operator which fundamentally alters the linear spectrum even for infinitesimal collisionality [Ng et al., Phys. Rev. Lett. 83, 1974(1999. A comparison between different discretization schemes reveals that a Hermite representation is superior for accurately resolving the spectra compared to a finite differences scheme using an equidistant velocity grid. Additionally, it is shown analytically that any even power of velocity space hyperdiffusion also produces a Case-Van Kampen spectrum which, in the limit of zero hyperdiffusivity, matches the collisionless Landau solutions. V C 2013 American Institute of Physics. [http://dx

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confidence: 99%

Aspects of linear Landau damping in discretized systems

et al. 2013

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“…Furthermore, subdominant instabilities are tracked employing the eigenvalue solver integrated into GENE, [49][50][51] which allows a more complete comparison between linear and nonlinear transport characteristics. For the present linear simulations, we employ a resolution of 31 × 64 × 64 × 16 in (k x , z, v , µ) dimensions, analyzing a single k y mode at a time.…”

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confidence: 99%

Characterizing turbulent transport in ASDEX Upgrade L-mode plasmas via nonlinear gyrokinetic simulations

et al. 2013

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The nature and level of turbulent transport in the outer core of low-confinement (L-mode) discharges performed at the ASDEX Upgrade tokamak [A. Kallenbach et al., Nucl. Fusion 51, 094012 (2011)] are examined. Previously, it was found that for an L-mode discharge of the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] gyrokinetic simulations were unable to reproduce the experimental ion heat flux, underestimating it by almost an order of magnitude. In the present work, employing the GENE gyrokinetic turbulence code, an extensive nonlinear study is performed for L-mode discharges of ASDEX Upgrade in order to cross-check this observation. It is shown that no systematic underprediction can be found in these simulations-instead, discrepancies with respect to experimental transport levels are small enough to be resolved within the uncertainties of the experimental profiles. Moreover, it is shown that some turbulence properties resemble closely those of the underlying linear microinstabilities at least out to 90% of the minor radius, so that quasilinear transport models remain in principle applicable even for these parameters, provided that appropriate nonlinear saturation rules can be developed.

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“…Both linear and non-linear simulations were performed. In the linear mode, an eigenvalue solver was used to compute multiple modes for each point in parameter space [36,37]. In the presence of rotation, when no time-independent eigenmodes can form, a complementary initial value solver was used.…”

Section: Gene Simulations and Discharge Parametersmentioning

confidence: 99%

Ion temperature profile stiffness: non-linear gyrokinetic simulations and comparison with experiment

et al. 2014

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Abstract. Recent experimental observations at JET show evidence of reduced ion temperature profile stiffness, hypothesised to be due to concomitant low magnetic shear (ŝ) and significant toroidal rotational flow shear. Non-linear gyrokinetic simulations are performed, aiming to investigate the physical mechanism behind the observations. A comprehensive set of simulations are carried out, comparing the impact on the ion heat flux of various parameters that differ within the data-set. These parameters include q,ŝ, rotation, effect of rotation on the magnetohydrodynamic (MHD) equilibrium, R/L n , β e , Z ef f , and the fast particle content. The effect of toroidal flow shear itself is not predicted by the simulations to lead to a significant reduction in ion heat flux, due both to an insufficient magnitude of flow shear and significant parallel velocity gradient destabilisation. It is however found that non-linear electromagnetic effects due to both thermal and fast-particle pressure gradients, even at low β e , can significantly reduce the profile stiffness. A total of five discharges are examined, at both inner and outer radii. For all cases studied, the simulated and experimental ion heat flux values agree within reasonable variations of input parameters around the experimental uncertainties.PACS numbers: 52.30. Gz, 52.35.Ra, 52.55.Fa, 52.65.Tt Ion temp. profile stiffness: non-lin. gyrokinetic simu. and comparison with exp.

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Multi-dimensional gyrokinetic parameter studies based on eigenvalue computations

Cited by 14 publications

References 23 publications

Aspects of linear Landau damping in discretized systems

Aspects of linear Landau damping in discretized systems

Characterizing turbulent transport in ASDEX Upgrade L-mode plasmas via nonlinear gyrokinetic simulations

Ion temperature profile stiffness: non-linear gyrokinetic simulations and comparison with experiment

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