Abstract Details
Abstracts
Author: Brady Elster
Requested Type: Poster
Submitted: 2026-03-21 06:51:28
Co-authors: Luca Guazzotto, Evdokiya Kostadinova
Contact Info:
Auburn University
380 Duncan Drive
Auburn, Alabama 36832
United States
Abstract Text:
Equilibrium flows play a key role in determining stability in tokamaks, and their effects have been studied extensively within single-fluid models. In a two-fluid description, however, equilibrium rotation is tied to "flow surfaces" that are close to, but distinct from, magnetic surfaces, giving rise to a velocity component normal to the magnetic surfaces. This "normal flow" is expected to qualitatively modify the behavior of magnetic-surface-localized instabilities, such as tearing modes. We present an analytical investigation using the slab approximation and the reduced-MHD equations under the presence of two-fluid equilibrium flow. The poloidal periodicity of the normal flow introduces coupling between poloidal harmonics or "sidebands", and resistive layer equations gain additional advection terms dependent on odd derivatives of these sidebands. We present a realistic scaling of small parameters called a "distinguished limit", consistent with simulations from the FLOW2 code [1] for DIII-D and NSTX-like equilibria. This systematic approach identifies how the dominant physical balances shift across radial regions as the resonant surface is approached, enabling consistent perturbative expansions when necessary. Under the constant-flux approximation, we generalize the classic Rutherford-Furth solution and show progress in deriving analytic expressions for the tearing stability index as a function of the equilibrium flow speeds. These analytical findings are compared against numerical simulations to obtain eigenfunction profiles for the perturbed velocity and magnetic field.
This work is supported by DE-SC0023061, DE-SC0024547, and DE-SC0014196.
[1] L. Guazzotto and R. Betti, "Two-fluid equilibrium with flow: FLOW2", Physics of Plasmas, vol. 22, no. 9, 2015, Art. no. 092512.
Characterization: 1.0
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