Abstract Details
Abstracts
Author: Gary M Staebler
Requested Type: Consider for Invited
Submitted: 2023-03-14 10:08:54
Co-authors: J. Candy, E. A. Belli
Contact Info:
ORNL
PO Box 2001
Oak Ridge, TN 37831
USA
Abstract Text:
Gyro-fluid equations are velocity space moments of the gyrokinetic equation. Special gyro-Landau-fluid closures have been developed to include the damping due to kinetic resonances by fitting to the collisionless local plasma response functions. This damping allows for accurate linear eigenmodes to be computed with a relatively low number of velocity space moments compared to gyrokinetic codes. However, none of the published gyro-Landau-fluid closure schemes preserve the Onsager symmetries of the resulting quasilinear fluxes. Onsager symmetry guarantees that the matrix of diffusivities is positive definite, an important property for the numerical stability of a transport solver. A very simple closure scheme for regularizing the gyro-fluid equations, that preserves the Onsager symmetry and is scalable to higher velocity space moments, has been developed. The new linear gyro-fluid eigensolver (GFS) is used to extend the TGLF quasilinear transport model so that it can compute the energy and momentum fluxes due to parallel magnetic fluctuations, completing the transport matrix. The GFS equations do not use a bounce average approximation. The GFS equations are fully electromagnetic, with general flux surface magnetic geometry, pitch angle scattering for electron collisions and subsonic equilibrium rotation. The TGLF transport model, with the new GFS eigensolver, can output the symmetric diffusion and convection response matrices for each species. This will be particularly helpful for multi-ion species plasmas transport studies. The TGLF fluxes for different number of velocity and parallel space moments are verified with CGYRO linear eigenmodes using the same saturation model. Prospects for future applications of quasilinear theory to new plasma transport regimes and magnetic confinement devices in addition to tokamaks are opened by the flexibility of the GFS eigensolver.
This work was supported by the U.S. Department of Energy under DE-FG02-95ER54309 and DE-AC05-00OR22
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