嵌入原行星盘的行星包层中的尘埃传输：I. 对流稳定包层
Dust transport in envelopes of disk-embedded planets: I. Convectively stable envelopes
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中文总结 AI 辅助
研究嵌入原行星盘的类地行星包层尘埃传输，通过多流体模拟发现对流稳定包层尘埃极度贫乏，可加速失控气体吸积，深部富集需大 pebble 输送后分解或升华。
中文摘要 AI 辅助
嵌入原行星盘的行星通过其气体包层吸积固体物质，行星包层内尘埃粒子的空间分布目前了解甚少。我们开展了高分辨率二维和三维多流体模拟，追踪质量与地球相近的行星周围气体和尘埃的动力学过程。模拟结果揭示了外层的循环流以及被该循环流屏蔽的内部对流稳定包层。我们发现存在尘埃极度贫乏的包层：尘埃气比沿径向向内递减，在包层深部（小于0.1倍Bondi半径，$R_{\rm B}$），其数值比包层外边缘降低了2至4个数量级。无量纲停止时间${\rm St}\backsimeq10^{-3}$的小颗粒会被裹挟在循环流中，无法进入包层；而${\rm St}\backsimeq10^{-2}$的大颗粒则能穿透包层，但会沿中平面快速沉降至核心。对流稳定包层中的尘埃贫乏意味着包层大部分区域的尘埃不透明度大幅降低，这有助于冷却，加速向失控吸积气体的转变。这些结果进一步表明，若要在包层深部（小于0.1倍$R_{\rm B}$）富集尘埃或挥发物，需要通过大 pebble 输送，随后大 pebble 在包层深部分解或从宿主颗粒升华。
英文摘要
Planets embedded in protoplanetary disks accrete solids through their gaseous envelopes. The spatial distribution of these dust particles inside the envelopes of disk-embedded planets is poorly known. We present high-resolution two- and three-dimensional multifluid simulations that follow the dynamics of gas and dust around planets similar in mass to Earth. Our simulations resolve an outer recycling flow and an inner convectively stable envelope that is shielded from the recycling flow. We identify strongly dust-depleted envelopes: the dust-to-gas ratio decreases radially inward and is reduced by more than two to four orders of magnitude in the deep interior ($<0.1\,R_{\rm B}$; Bondi radius) compared to its value at the outer edge of the envelope. Small grains, with a dimensionless stopping time ${\rm St}\lesssim10^{-3}$, remain entrained in the recycling flow and do not enter the envelope, whereas large grains (${\rm St}\gtrsim10^{-2}$) penetrate the envelope but settle rapidly onto the core along the midplane. The resulting dust depletion in convectively-stable envelopes implies a substantial reduction in dust opacity throughout much of the envelope, facilitating cooling and a more rapid transition to runaway gas accretion. These results further suggest that enriching the deep envelope ($<0.1\,R_{\rm B}$) with dust or volatiles requires their delivery through large pebbles that then subsequently disintegrate, or sublimate, from their host grains in the deep envelope interior.
