AI 中文总结
本研究通过DISPATCH框架的3D理想磁流体动力学模拟，揭示原行星盘跨尺度吸积机制，发现流丝与盘相互作用会改变盘结构，后期吸积主要沿中平面和表层进行，外盘暂不适宜行星形成。
AI 中文摘要
原行星盘围绕新生恒星演化，其演化过程由周围湍流云物质的吸积、向年轻恒星的吸积以及外流驱动的质量损失三者共同作用决定。长期以来，确定原行星盘的物质主要是沿盘的中平面还是沿两极供给，以及吸积是稳态还是爆发式的，一直是一项挑战。在此，我们使用自适应网格细化框架DISPATCH，在动态的大尺度分子云环境中开展了一系列3D理想磁流体动力学模拟，研究原行星盘的形成与演化。我们聚焦9个恒星系统，将原行星盘的分辨率细化至0.8天文单位（au）的尺度。在整个样本范围内，恒星吸积在10万年（10⁵年）的时间尺度上以约10⁻⁵太阳质量每年（M☉ yr⁻¹）的速率进行，且存在显著的变异性。原行星盘可生长至100 au的尺度，且在时间上保持引力稳定，盘与恒星的质量比低于10%。具有1万年（10 kyr）吸积时间的瞬态高密度流丝，可驱动各向异性的物质输运，其速率与背景吸积流相当。流丝与原行星盘的相互作用通常会导致盘的尺寸暂时缩小一半，盘质量减少40%。在原行星盘演化的后期静止阶段（t≳50 kyr），吸积主要发生在中平面和盘表层，这与环形磁场结构的形成相关，该结构在两个盘面处均存在磁场反转。通过这种方式，整个盘的质量储备可在10 kyr的时间尺度上得到补充。这些发现表明，当极年轻的外盘电离充分且接近理想磁流体动力学（MHD） regime时，由于高补充率、强湍流以及破坏性的流丝吸积事件，该区域尚不具备行星形成的有利条件。
英文摘要
Protoplanetary discs evolve around newly-formed stars through an interplay of infall from surrounding turbulent cloud material, accretion towards the young star, and outflow driven mass-loss. It has been challenging to determine if discs are fed predominantly through infall along the disc midplane, or along the poles, and if accretion occurs in a steady or burst-like fashion. Here, we present a suite of 3D ideal magnetohydrodynamical simulations of protoplanetary disc formation and evolution in a dynamic, large-scale molecular cloud environment using the adaptive mesh refinement framework DISPATCH. We focus on nine stellar systems, where we resolve discs down to a scale of 0.8 au. Across the sample, stellar accretion proceeds at rates of $\sim$10$^{-5}$ M$_\odot$ yr$^{-1}$ over 10$^{5}$ yr, with significant variability. Discs grow to 100 au scales and remain gravitationally stable in time, with disc-to-star mass ratios below 10 %. Transient high-density streamers, with 10 kyr infall times, can drive anisotropic mass delivery at rates comparable to the background accretion flow. Their interaction with discs typically results in a temporary reduction of the disc size by half, and disc mass by 40 %. During later quiescent disc evolution stages ($t\gtrsim$50 kyr), accretion predominantly occurs through the midplane and disc surface layers. This is associated with the development of a toroidal magnetic field morphology, which includes field reversals across both disc surfaces. In this way, the full disc mass reservoir is replenished on 10 kyr-timescales. These findings support that the outer parts of very young discs, when well-ionised and close to the ideal MHD regime, are not yet conducive to planet formation, due to high replenishment rates, strong turbulence, and disruptive streamer infall events.
Comments21 pages, 19 figures
