Abstract Details
Abstracts
Author: Jeff Candy
Requested Type: Consider for Invited
Submitted: 2025-02-19 13:48:42
Co-authors: A. Dudkovskaia, E. Belli
Contact Info:
General Atomics
3550 General Atomics Court
San Diego, CA 92121
USA
Abstract Text:
In this work we detail a new mathematical framework to carry out global gyrokinetic simulation by a suitable modification of the existing local formulation. Although global simulations have been routine for more than 20 years, systematic quantification of global corrections to the precise local limit have been lacking in both the gradient-driven and flux-driven formalisms. A key obstacle in this quantification has been the inability to remove artificial shearing generated by global Dirichlet boundary conditions and associated artificial plasma profile shapes. In the new method, global curvature corrections are introduced asymptotically via the application of a discrete radial wavenumber advection operator. This approach enables a high-precision global simulation capability without sacrificing the efficiency and spectral accuracy of local simulations. Numerical results demonstrate that there are two distinct types of global correction to the local result: (1) a shift of the local result in radius due to variation of the effective temperature and density gradient scale length, (2) a decorrelation leading to turbulence suppression, similar to the well-known ExB shear effect. Corrections (1) and (2) are fully quantified by a handful of new physics parameters which measure the profile curvature (second derivatives, and products of first derivatives). This interpretation in terms of radial shift and nontrivial decorrelation provides a simple framework for more accurate interpretation of global gyrokinetic theory. This work has been submitted to Phys. Rev. Letters, and was supported by US DOE under DE-FG02-95ER54309 and DE-SC0024425 (FRONTIERS SciDAC-5 project).
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