The global dynamics of geodesic acoustic modes (GAMs) is studied analytically and by means of gyrokinetic simulations for several equilibria with flat and nonuniform profiles. In particular, the effects of phase mixing via the continuum spectrum in the presence of a temperature gradient are investigated. We show that the frequency of GAM is not constant but can evolve in time because of the increase of the radial wavenumber. As a consequence, also the radial velocity of GAM increases in time. Thus, this study reduces the discrepancy between the linear theory and the experiments, in which strong velocities of GAM are generally observed. An estimate of phase and group velocity is given for simulations performed with experimental parameter values. Published by AIP Publishing.
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EURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, France
Univ Saskatchewan, Saskatoon, SK S7N 5E2, CanadaEURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, France
Smolyakov, A. I.
Nguyen, C.
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EURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, FranceEURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, France
Nguyen, C.
Garbet, X.
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EURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, FranceEURATOM, CEA,DSM,DRFC, Ctr Cadarache, F-13108 St Paul Les Durance, France
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Natl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Natl Res Nucl Univ MEPhI, Moscow 115409, RussiaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Melnikov, A. V.
Eliseev, L. G.
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Natl Res Ctr Kurchatov Inst, Moscow 123182, RussiaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Eliseev, L. G.
Lysenko, S. E.
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Natl Res Ctr Kurchatov Inst, Moscow 123182, RussiaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Lysenko, S. E.
Perfilov, S. V.
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Natl Res Ctr Kurchatov Inst, Moscow 123182, RussiaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Perfilov, S. V.
Shurygin, R. V.
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Natl Res Ctr Kurchatov Inst, Moscow 123182, RussiaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia
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Natl Res Ctr Kurchatov Inst, Moscow 123182, Russia
Univ Saskatchewan, Saskatoon, SK S7N 5E2, CanadaNatl Res Ctr Kurchatov Inst, Moscow 123182, Russia