Abstract Details
Abstracts
Author: Erik C. Hansen
Requested Type: Consider for Invited
Submitted: 2026-03-09 23:57:45
Co-authors: W. Barham, P.J. Morrison, D.R. Hatch, S.M. Mahajan
Contact Info:
University of Texas, Austin
2515 Speedway, C1600
Austin, TX 78712
United States
Abstract Text:
Understanding plasma behavior requires accurate modeling of the turbulent enhancement of particle and energy transport. We examine three descriptions of nonlinear plasma dynamics to evaluate their physical consistency. To describe turbulence, the Kuramoto-Sivashinsky equation balances fluid advection, energy input, and hyper-dissipation. The instabilities in this simple system can produce patterns in generic turbulent phenomena, from the flow of water down a hill to the tokamak trapped ion mode. But we show that it cannot be considered thermodynamically consistent, as its anti-diffusive forcing would require a negative entropy.[arXiv:2601.05389] By contrast, the incompressible Hall MHD equations have been justified by the plasma two-fluid theory and describe fluid plasma phenomena on the order of the ion skin depth. We simulate the turbulence of circularly polarized Alfvén waves in this model, constructing three-wave interactions which survive the linear timescale for fusion and astrophysical plasma conditions. The predicted exact time for a three-wave system to evolve is compared to timescales defined numerically. Yet a simpler model than extended MHD which retains physical consistency is the three-field model due to Hazeltine. This model couples the reduced MHD description of large aspect ratio fusion devices, the Hasegawa-Mima electrostatic turbulence, and Ohmic dissipation. When a background density gradient is added to this model, we can recover the Hasegawa-Wakatani equations in a way that spotlights Ohmic dissipation as the driver of this instability. By understanding the consistency of these models of plasma turbulence, we can develop more appropriate explanations of next-generation fusion plasma behavior.
Characterization: 1.0
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