Decay of geodesic acoustic modes due to the combined action of phase mixing and Landau damping

A. Biancalani, F. Palermo, C. Angioni, A. Bottino, F. Zonca

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Abstract

Geodesic acoustic modes (GAMs) are oscillations of the electric field whose importance in tokamak plasmas is due to their role in the regulation of turbulence. The linear collisionless damping of GAMs is investigated here by means of analytical theory and numerical simulations with the global gyrokinetic particle-in-cell code ORB5. The combined effect of the phase mixing and Landau damping is found to quickly redistribute the GAM energy in phase-space, due to the synergy of the finite orbit width of the passing ions and the cascade in wave number given by the phase mixing. When plasma parameters characteristic of realistic tokamak profiles are considered, the GAM decay time is found to be an order of magnitude lower than the decay due to the Landau damping alone, and in some cases of the same order of magnitude of the characteristic GAM drive time due to the nonlinear interaction with an ion-temperature-gradient (ITG) mode. In particular, the radial mode structure evolution in time is investigated here and reproduced quantitatively by means of a dedicated initial value code and diagnostics.
Original languageEnglish
Article number112115
Pages (from-to)-
JournalPhysics of Plasmas
Volume23
Issue number11
DOIs
Publication statusPublished - 1 Nov 2016
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

Biancalani, A., Palermo, F., Angioni, C., Bottino, A., & Zonca, F. (2016). Decay of geodesic acoustic modes due to the combined action of phase mixing and Landau damping. Physics of Plasmas, 23(11), -. [112115]. https://doi.org/10.1063/1.4967703