Abstract Details
Abstracts
Author: Alexandre P Sainterme
Requested Type: Poster
Submitted: 2025-03-14 11:08:10
Co-authors: Fatima Ebrahimi
Contact Info:
Princeton University
4 Ivy Ln
Princeton, NJ 08544
USA
Abstract Text:
Large-scale Instabilities in fusion-grade plasmas may be modified both by the presence of sheared flows and via two-fluid (e.g., Hall) effects. This may be particularly important in the edge, where length scales can be comparable to the ion skin depth. Steady, super-Alfvenic azimuthal flows in a cylinder threaded with an axial magnetic field are unstable to magnetorotational instabilities (MRI). For non-axisymmetric perturbations, the linear MHD system exhibits global `magneto-curvature’ (MCI) modes in addition to the typical local non-axisymmetric MRI modes (Ebrahimi, et al. ApJ 936:145 2022). These modes are unstable over larger parameter ranges than the MRI, and persist for sub-Alfvenic flows in the case of an azimuthal magnetic field. The existence of global MCI modes in the sub-Alfvenic flow, strong magnetic field regime suggests that they may be relevant for rotating fusion plasmas. With the inclusion of the Hall term in the extended MHD Ohm’s law, the parameter range over which the axisymmetric MRI modes are unstable is modified (Wardle MNRAS 307 1999, Balbus and Terquem ApJ 552 2001, Ebrahimi PoP 18 2011). This work presents the development of a local dispersion relation for the linear Hall-MHD equations for non-axisymmetric modes in a sheared azimuthal flow. Numerical solutions of the global radial eigenvalue problem show that the Hall term increases the growth rate of the non-axisymmetric MRI, and does not significantly alter the more global MCI modes in the vertical magnetic field case. Results from an eigenvalue solver are compared with linear initial-value calculations using the NIMROD code. Nonlinear NIMROD simulations including the Hall term show the generation of larger-scale magnetic structures that are absent in MHD case.
Work supported by the U.S. National Science Foundation award #2308829
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