Excitation of beta-induced Alfvén eigenmodes in the presence of a magnetic island

Observation of magnetic activity in several discharges in the Frascati Tokamak Upgrade has revealed high-frequency oscillations that accompany the development of large magnetic islands in ohmic plasmas. The frequency of these oscillations is one order of magnitude above the typical island rotation f...

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Bibliographic Details
Published in:Plasma physics and controlled fusion 2007-04, Vol.49 (4), p.475-483
Main Authors: Annibaldi, S V, Zonca, F, Buratti, P
Format: Article
Language:English
Subjects:
Compressibility
Eigenvalues and eigenfunctions
Electric discharges
Energy gap
Natural frequencies
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Summary:Observation of magnetic activity in several discharges in the Frascati Tokamak Upgrade has revealed high-frequency oscillations that accompany the development of large magnetic islands in ohmic plasmas. The frequency of these oscillations is one order of magnitude above the typical island rotation frequency and one order of magnitude below the toroidicity-induced gap of the shear-Alfvén continuum. By writing a precise dispersion relation, we interpret these modes as beta-induced Alfvén eigenmodes, i.e. Alfvén eigenmodes located in the low frequency gap which is caused by finite compressibility.
ISSN:0741-3335
1361-6587
1361-6587
DOI:10.1088/0741-3335/49/4/010