磁旋转驱动的湍流盘中的尘埃沉降I：数值方法和强流动不稳定性的证据
Dust Settling in Magnetorotationally-Driven Turbulent Discs I: Numerical Methods and Evidence for a Vigorous Streaming Instability
摘要：
本文用计算天体物理学的RIEMANN程序研究了垂直分层的原恒星吸积盘中真实分布的尘埃颗粒与气体的相互作用。圆盘被模拟为具有最小质量太阳星云的密度和温度，并通过磁旋转不稳定性（MRI）被驱动到充分发展的湍流。我们发现，包括标准的尘埃气体比例没有任何显着的影响，即使当尘埃沉积到吸积盘的中平面的MRI。尘埃的密度分布达到高斯分布，我们得到的尘埃的刻度高度被证明是成比例的尘埃半径的平方根的倒数。最大的尘埃显示出强烈的倾向，沉降到吸积盘的中平面，并倾向于组织成高密度的细长团块。这些团块的动态被证明是一致的流不稳定性。流动不稳定性被认为是非常有力的和持久的，一旦它形成。每一个高密度的尘埃流显示出一个减少的RMS速度分散，和密集的大尘埃结块的流相交的地方形成。我们还表明，平均自由程和碰撞时间的尘埃，参与流不稳定性减少了近两个数量级的平均自由程和碰撞时间。我们发现，在我们的10个Au模拟的一些大的灰尘应该有倾向于颗粒聚结。
英文摘要：
(Abridged) In this paper we have used the RIEMANN code for computational astrophysics to study the interaction of a realistic distribution of dust grains with gas in a vertically stratified protostellar accretion disc. The disc was modeled to have the density and temperature of a minimum mass solar nebula, and was driven to a fully-developed turbulence via the magnetorotational instability (MRI). We find that the inclusion of standard dust to gas ratios does not have any significant effect on the MRI even when the dust sediments to the midplane of the accretion disc. The density distribution of the dust reaches a Gaussian profile, and the scale heights for the dust that we derive are shown to be proportional to the reciprocal of the square root of the dust radius. The largest dust shows a strong tendency to settle to the midplane of the accretion disc, and tends to organize itself into elongated clumps of high density. The dynamics of these clumps is shown to be consistent with a streaming instability. The streaming instability is seen to be very vigorous and persistent once it forms. Each stream of high density dust displays a reduced RMS velocity dispersion, and the densest clumpings of large dust are shown to form where the streams intersect. We have also shown that the mean free path and collision time for the dust that participates in the streaming instability is reduced by almost two orders of magnitude relative to the average mean free paths and collision times. We show that some of the large dust in our 10 au simulations should have a propensity for grain coalescence.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
