In this work, we highlight an issue that may reduce the accuracy of many local nonlinear gyrokinetic simulations – turbulent self-interaction through the parallel boundary condition. Given a sufficiently long parallel correlation length, individual turbulent eddies can span the full domain and ‘bite their own tails’, thereby altering their statistical properties. Such self-interaction is only modelled accurately when the simulation domain corresponds to a full flux surface, otherwise it is artificially strong. For Cyclone Base Case parameters and typical domain sizes, we find that this mechanism modifies the heat flux by approximately 40 % and it can be even more important. The effect is largest when using kinetic electrons, low magnetic shear and strong turbulence drive (i.e. steep background gradients). It is found that parallel self-interaction can be eliminated by increasing the parallel length and/or the binormal width of the simulation domain until convergence is achieved.

中文翻译：

---

通过局部陀螺动力学模拟中的平行边界条件消除湍流自相互作用

在这项工作中，我们强调了一个可能会降低许多局部非线性陀螺动力学模拟准确性的问题——通过平行边界条件的湍流自相互作用。给定足够长的平行相关长度，单个湍流涡流可以跨越整个域并“咬住自己的尾巴”，从而改变它们的统计特性。这种自相互作用只有在模拟域对应于全通量表面时才能准确建模，否则它是人为的强。对于 Cyclone Base Case 参数和典型域大小，我们发现这种机制将热通量修改了大约 40%，而且它可能更加重要。当使用动能电子、低磁剪切和强湍流驱动（即陡峭的背景梯度）时，效果最大。