The shear Alfvén continuum with a magnetic island chain in tokamak plasmas
Abstract The shear Alfvén continuum spectrum is studied for a tokamak with a single island chain using the ideal magnetohydrodynamics theory. We have taken into account the toroidal geometry and toroidal mode coupling with the island considered as a highly-shaped stellarator. Various new frequency g...
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crioppubl:10.1088/1361-6587/aca9f8 2024-09-15T18:41:48+00:00 The shear Alfvén continuum with a magnetic island chain in tokamak plasmas Qu, Z S Hole, M J National Computational Infrastructure Australian Research Council Simons Foundation 2022 http://dx.doi.org/10.1088/1361-6587/aca9f8 https://iopscience.iop.org/article/10.1088/1361-6587/aca9f8 https://iopscience.iop.org/article/10.1088/1361-6587/aca9f8/pdf unknown IOP Publishing https://iopscience.iop.org/page/copyright https://iopscience.iop.org/info/page/text-and-data-mining Plasma Physics and Controlled Fusion volume 65, issue 2, page 025002 ISSN 0741-3335 1361-6587 journal-article 2022 crioppubl https://doi.org/10.1088/1361-6587/aca9f8 2024-08-12T04:14:56Z Abstract The shear Alfvén continuum spectrum is studied for a tokamak with a single island chain using the ideal magnetohydrodynamics theory. We have taken into account the toroidal geometry and toroidal mode coupling with the island considered as a highly-shaped stellarator. Various new frequency gaps open up inside the island due to its asymmetry both poloidally and toroidally, such as the mirror-induced Alfvén eigenmode (MAE) gap and the helicity-induced Alfvén eigenmode (HAE) gap. We have shown that the MAE gap acts as the continuation of the outside toroidal Alfvén eigenmode (TAE) gap into the island. However, the combined TAE/MAE gap is getting narrower as the island grows, leaving only half of its original width with a moderate island size as much as 3.2% of the minor radius. In addition, the two-dimensional eigenfunction of the continuum mode on the lower tip of the MAE gap now has highly localised structures around the island’s long axis, contrary to the usual oscillatory global solutions found with no or a low level of toroidal asymmetry—an indication of the continuous spectrum becoming discrete and dense. These results have implications for the frequency, mode structure and continuum damping of global TAEs residing in the gap. Article in Journal/Newspaper Magnetic Island Single Island IOP Publishing Plasma Physics and Controlled Fusion 65 2 025002 |
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Abstract The shear Alfvén continuum spectrum is studied for a tokamak with a single island chain using the ideal magnetohydrodynamics theory. We have taken into account the toroidal geometry and toroidal mode coupling with the island considered as a highly-shaped stellarator. Various new frequency gaps open up inside the island due to its asymmetry both poloidally and toroidally, such as the mirror-induced Alfvén eigenmode (MAE) gap and the helicity-induced Alfvén eigenmode (HAE) gap. We have shown that the MAE gap acts as the continuation of the outside toroidal Alfvén eigenmode (TAE) gap into the island. However, the combined TAE/MAE gap is getting narrower as the island grows, leaving only half of its original width with a moderate island size as much as 3.2% of the minor radius. In addition, the two-dimensional eigenfunction of the continuum mode on the lower tip of the MAE gap now has highly localised structures around the island’s long axis, contrary to the usual oscillatory global solutions found with no or a low level of toroidal asymmetry—an indication of the continuous spectrum becoming discrete and dense. These results have implications for the frequency, mode structure and continuum damping of global TAEs residing in the gap. |
author2 |
National Computational Infrastructure Australian Research Council Simons Foundation |
format |
Article in Journal/Newspaper |
author |
Qu, Z S Hole, M J |
spellingShingle |
Qu, Z S Hole, M J The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
author_facet |
Qu, Z S Hole, M J |
author_sort |
Qu, Z S |
title |
The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
title_short |
The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
title_full |
The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
title_fullStr |
The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
title_full_unstemmed |
The shear Alfvén continuum with a magnetic island chain in tokamak plasmas |
title_sort |
shear alfvén continuum with a magnetic island chain in tokamak plasmas |
publisher |
IOP Publishing |
publishDate |
2022 |
url |
http://dx.doi.org/10.1088/1361-6587/aca9f8 https://iopscience.iop.org/article/10.1088/1361-6587/aca9f8 https://iopscience.iop.org/article/10.1088/1361-6587/aca9f8/pdf |
genre |
Magnetic Island Single Island |
genre_facet |
Magnetic Island Single Island |
op_source |
Plasma Physics and Controlled Fusion volume 65, issue 2, page 025002 ISSN 0741-3335 1361-6587 |
op_rights |
https://iopscience.iop.org/page/copyright https://iopscience.iop.org/info/page/text-and-data-mining |
op_doi |
https://doi.org/10.1088/1361-6587/aca9f8 |
container_title |
Plasma Physics and Controlled Fusion |
container_volume |
65 |
container_issue |
2 |
container_start_page |
025002 |
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1810486192541532160 |