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Author(s):
T. Watari, Y. Hamada, A. Nishizawa, J. Todoroki and K. Itoh
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Title:
Unified Linear Response Function for the Stationary Zonal Flow and the Geodesic Acoustic Mode
Date of publication:
Sep. 2005
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Key words:
zonal flow, geodesic acoustic mode, kinetic description, response function, finite orbit effects
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Abstract:
This paper presents a formulation of linear response function of electrostatic potential to the nonlinear drives, which is important in considering the self-regulation of the turbulence. There are two well-known branches, stationary zonal flow and Geodesic Acoustic mode, which are known to have weak damping rate and therefore have been believed to regulate the turbulences. Since the frequencies of these modes are in so different regimes, these branches have been analyzed separately with proper approximations. This paper gives unified expressions of these response functions. Drift kinetic equation is integrated along particle orbits by expressing particle orbits in Fourier series expansion. The obtained formula disclosed some interesting aspects of the response function, for example, the existence of a low frequency Geodesic Acoustic Mode and the harmonic resonance effects of individual particles.
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