Abstract Details
Abstracts
Author: Zhenyu Wang
Requested Type: Consider for Invited
Submitted: 2025-02-20 12:48:00
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Contact Info:
Institute of Plasma Physics, CAS
350 Shushan Lake Rd.
Hefei, Anhui 230031
China
Abstract Text:
We have studied the quasi-kinetic equilibrium with spatial inhomogeneity and instability driven by ion temperature gradient by six-dimensional (6D) full-f particle-in-cell (PIC) simulations. In a system with spatial inhomogeneity, fluid equilibrium can be established straightforwardly, but there is no known suitable analytical equilibrium that satisfies the time-independent Vlasov-Maxwell system exactly. Full-f simulations with 6D ions and adiabatic electrons are carried out by a geometric structure preserving PIC algorithm[1] on unstructured mesh to search for a quasi-kinetic equilibrium with spatial inhomogeneity. The time evolution of density, ion-temperature and ion-velocity profiles are obtained, and the time-dependent ion distribution function is also numerically constructed. The frequency spectrum of the density, ion-temperature, ion-velocity, ion distribution function from the PIC simulation is compared to the timescale analysis of the dynamics of the Vlasov equation. We find the 6D gyromotion has formed an equilibrium velocity-shear in the poloidal direction. An instability appears on the top of this velocity-shear in the region of the strong temperature gradient with the inhomogeneity scale length of only a few ion gyroradii. By comparing to the five-dimensional (5D) gyrokinetic analysis[2], we confirm the instability driven by ion temperature gradient instead of the equilibrium velocity shear. It is demonstrated that the 5D gyrokinetic theory predicts the instability qualitatively consistent with the 6D full-f simulation, but the quantitative comparison shows the obvious divergence between the 5D gyrokinetic and the 6D fully-kinetic results. The study suggests the necessity to carry out fully kinetic 6D studies in strong gradient region like steep edge pedestal.
[1] Z. Wang, H. Qin, B. J. Sturdevant and C.S. Chang, J. Plasma. Phys., 2021.
[2] B. J. Sturdevant, Private Communication. 2023.
Characterization: 7.0
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