Fundamental properties of ideal and resistive infernal modes in tokamaks

Infernal modes are unstable in regions of weak magnetic shear and significant pressure gradients. These modes comprise a broad class of instabilities, encompassing interchange modes and kink modes, with both short and long length scales. Toroidal effects and fully electromagnetic fields are of cruci...

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Bibliographic Details
Published in:Plasma physics and controlled fusion 2024-09, Vol.66 (9), p.95004
Main Authors: Coste-Sarguet, M, Graves, J P
Format: Article
Language:English
Subjects:
infernal modes
interchange modes
internal kink modes
low shear
resistive tokamak instabilities
spectrum of instabilities
subdominant modes
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Summary:Infernal modes are unstable in regions of weak magnetic shear and significant pressure gradients. These modes comprise a broad class of instabilities, encompassing interchange modes and kink modes, with both short and long length scales. Toroidal effects and fully electromagnetic fields are of crucial importance for their description. The role of resistive diffusion and compressibility are also critical. In order to investigate this awkward problem while still enabling fundamental physics interpretation, a new resistive MHD eigensolver has been developed. An outcome of this study is the identification of an unstable spectrum of resistive infernal modes in regions of the plasma with weak average curvature, and in regions where the average curvature is destabilising. These fast growing modes may be collectively important for our understanding of global reconnection events, stochastic magnetic fields states, and neighbouring supercritical bifurcations.
ISSN:0741-3335
1361-6587
DOI:10.1088/1361-6587/ad5ff2