Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

Abstract

Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux -ṽ rñṽθ is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux ṽ rñṽθ in strong electrostatic turbulence is calculated using Hasegawa-Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.

Non-Oberbeck–Boussinesq zonal flow generation

“…This deviation is mainly reasoned in the triple fluctuation drive. Its importance in steep background density gradient regimes is in qualitative agreement with the theoretical estimate in the strong turbulence regime [38]. A similar dependence as for the Favre stress drive is found for the radial ZF advection mechanism.…”

“…Despite these obstacles Eq. ( 6) has been recently used to show that the second term, occasionally misinterpreted as advective, and the cubic term can be comparable to the Reynolds stress related drive ∂ x ( n R) [15,37,38]. Thus, we go a step further and utilize a density weighted Favre decomposition instead of the Reynolds decomposition according to h := [[h]] + h and [[h]] := nh / n [44].…”

How turbulence fronts induce plasma spin-up

“…The nonlinear flux requires a closure calculation. Recent works [16,17] report the calculations of the nonlinear flux in the strong turbulence regime. However, * kosuga@riam.kyushu-u.ac.jp the turbulence amplitude is typically at the level of the mixing length estimate, as reported from experiments [18,19] and simulations [20].…”

On the Application of Cross Bispectrum and Cross Bicoherence

“…They should be evaluated by cross-bispectrum [45][46][47][48][49][50]. First, if we consider the excitation of poloidal flow (radial electric field), the difference between…”