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 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.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

Compressibility

Eigenvalues and eigenfunctions

Electric discharges

Energy gap

Natural frequencies

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