Nonlinear gyrokinetic theory, the direct interaction approximation, and anomalous thermal transport in tokamaks

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Abstract
Invariance properties under scale transformations of the nonlinear gyrokinetic Vlasov and heat transport equations are used to examine anomalous thermal transport due to drift wave turbulence. To fully exploit the gyrokinetic expansion, separation of the fluctuations from the background by means of averaging is required. This leads to a statistical description of the system and the use of the direct interaction approximation. The invariance properties of the gyrokinetic and statistical descriptions produce the same results for χ, the thermal diffusivity. For a collisionless, low‐β, quasineutral plasma in a general magnetic field, a unique result is derived for χ.