The structure and evolution of protoplanetary discs (PPDs) are largely governed by disc angular momentum transport, mediated by magnetic fields. In the most observable outer disc, ambipolar diffusion is the primary non-ideal magnetohydrodynamic (MHD) effect. In this work, we study the gas dynamics in outer PPDs by conducting a series of global three-dimensional non-ideal MHD simulations with ambipolar diffusion and net poloidal magnetic flux, using the Athena++ MHD code, with resolution comparable to local simulations. Our simulations demonstrate the coexistence of magnetized disc winds and turbulence driven by the magneto-rotational instability (MRI). While MHD winds dominate disc angular momentum transport, the MRI turbulence also contributes significantly. We observe that magnetic flux spontaneously concentrates into axisymmetric flux sheets, leading to radial variations in turbulence levels, stresses, and accretion rates. Annular substructures arise as a natural consequence of magnetic flux concentration. The flux concentration phenomena show diverse properties with different levels of disc magnetization and ambipolar diffusion. The disc generally loses magnetic flux over time, though flux sheets could prevent the leak of magnetic flux in some cases. Our results demonstrate the ubiquity of disc annular substructures in weakly MRI turbulent outer PPDs and imply a stochastic nature of disc evolution.

中文翻译：

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具有双极扩散的外原行星盘的全局三维模拟

原行星盘 (PPD) 的结构和演化很大程度上受盘角动量传输的控制，由磁场介导。在最可观察到的外盘中，双极扩散是主要的非理想磁流体动力学 (MHD) 效应。在这项工作中，我们通过使用 Athena++ MHD 代码进行一系列具有双极扩散和净极向磁通量的全局三维非理想 MHD 模拟来研究外部 PPD 中的气体动力学，其分辨率可与局部模拟相媲美。我们的模拟证明了磁化盘风和由磁旋转不稳定性 (MRI) 驱动的湍流并存。虽然 MHD 风主导椎间盘角动量传输，但 MRI 湍流也有显着贡献。我们观察到磁通量自发地集中成轴对称的通量片，导致湍流水平、应力和吸积率的径向变化。环形子结构是磁通量集中的自然结果。通量集中现象表现出不同的特性，具有不同水平的圆盘磁化和双极扩散。磁盘通常会随着时间的推移失去磁通量，尽管在某些情况下通量片可以防止磁通量泄漏。我们的研究结果表明，在弱 MRI 湍流外部 PPD 中普遍存在椎间盘环状亚结构，并暗示椎间盘进化的随机性。磁盘通常会随着时间的推移失去磁通量，尽管在某些情况下通量片可以防止磁通量泄漏。我们的研究结果表明，在弱 MRI 湍流外部 PPD 中普遍存在椎间盘环状亚结构，并暗示椎间盘进化的随机性。磁盘通常会随着时间的推移失去磁通量，尽管在某些情况下通量片可以防止磁通量泄漏。我们的研究结果表明，在弱 MRI 湍流外部 PPD 中普遍存在椎间盘环状亚结构，并暗示椎间盘进化的随机性。