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Author: Jian Bao
Requested Type: Pre-Selected Invited
Submitted: 2017-03-17 22:08:51

Co-authors: D. Liu, Z. Lin

Contact Info:
University of California, Irvine
4184 FRH, UC Irvine
Irvine, CA   92697
US

Abstract Text:
Electromagnetic gyrokinetic particle simulation with kinetic electrons is computationally challenging in the perturbative (δf) gyrokinetic particle simulation, especially for collision-less tearing modes. We show that [1] this numerical difficulty arises from the fact that perturbed electron density and current measured from kinetic markers do not satisfy electron continuity equation in the conventional δf scheme due to electron noises. Consequently, electrostatic potential calculated from the density and parallel vector potential calculated from the current are not consistent with each other, which results in an unphysically large parallel electric field. This problem of electromagnetic simulation with kinetic electrons can be resolved in a “conservative scheme” [1] by applying the electron continuity equation to time-advance the electron density perturbation using the perturbed current calculated from the perturbed distribution function. Based on this finding, we propose a new nonlinear particle simulation model that incorporates low frequency electromagnetic fluctuations with both tearing parity and non-tearing parity [2]. This new simulation model has been implemented in the gyrokinetic toroidal code (GTC). The dispersion relations of kinetic Alfven wave and collision-less tearing mode from GTC simulations have been verified with analytic theory by using this new model, and it shows that the perpendicular grid size does not need to resolve the electron skin depth for the numerical accuracy and stability when the physical scale is beyond the electron skin depth. This new model will be utilized for gyrokinetic particle simulations of micro-tearing mode and neoclassical tearing mode in tokamaks.
[1] J. Bao and Z. Lin, http://arxiv.org/abs/1702.01406 (2017).
[2] J. Bao, D. Liu and Z. Lin, http://arxiv.org/abs/1702.01407 (2017).

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