Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for kinetic passing electron dynamics and is known to generate stationary $E\times B$ zonal flow shear layers at radial locations near low-order mode rational surfaces (Weikl et al. Phys. Plasmas, vol. 25, 2018, 072305). We find that self-interaction, in fact, plays a very significant role in also generating fluctuating zonal flows, which is critical to regulating turbulent transport throughout the radial extent. Unlike the usual picture of zonal flow drive in which microinstability eigenmodes coherently amplify the flow via modulational instabilities, the self-interaction drive of zonal flows from these eigenmodes are uncorrelated with each other. It is shown that the associated shearing rate of the fluctuating zonal flows therefore reduces as more toroidal modes are resolved in the simulation. In simulations accounting for the full toroidal domain, such an increase in the density of toroidal modes corresponds to an increase in the toroidal system size, leading to a finite system size effect that is distinct from the well-known profile shearing effect.

中文翻译：

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本征模态自相互作用如何影响带状流动和托卡马克核心湍流与环形系统尺寸的收敛

自相互作用是沿平行于磁场的方向延伸的微不稳定性本征模与其自身非线性相互作用的过程。这种效应在考虑动力学传递电子动力学的陀螺动力学模拟中特别显着，并且已知会产生静止的 $E\乘以 B$ 低阶模态有理面附近径向位置的纬向流剪切层（Weikl等。物理。等离子, 卷。25, 2018, 072305)。我们发现，事实上，自相互作用在产生波动的纬向流方面也起着非常重要的作用，这对于调节整个径向范围内的湍流传输至关重要。与通常的纬向流动驱动图不同，其中微不稳定性本征模式通过调制不稳定性相干放大流动，来自这些本征模式的纬向流动的自相互作用驱动彼此不相关。结果表明，随着在模拟中解析更多的环形模式，脉动带状流的相关剪切速率因此降低。在考虑整个环形域的模拟中，环形模式密度的这种增加对应于环形系统尺寸的增加，