论文标题
关于流媒体磁盘的流媒体不稳定性和垂直剪切不稳定性的共存
On the coexistence of the streaming instability and the vertical shear instability in protoplanetary disks
论文作者
论文摘要
流媒体不稳定性是解释行星图的形成的主要候选机制。然而，鉴于其作为线性流体动力学不稳定的基本性质，这种不稳定性在驱动湍流中的作用尚未详细研究。我们研究了流媒体不稳定性引起的湍流及其与垂直剪切不稳定性的相互作用。为此，我们使用闪存代码进行二维轴对称全球磁盘模拟，跨越半径从$ 1 $ au到$ 100 $ au，包括气体和灰尘之间的相互阻力以及径向和垂直恒星重力。如果流媒体不稳定性和垂直剪切不稳定性同时开始生长，我们发现尘埃中间平面层中的湍流主要由流媒体不稳定性驱动。它产生了垂直气体运动，其马赫数最多可达$ {\ sim} 10^{ - 2} $。尘埃尺度的高度以自我调节方式设置为大约$ 1 \％的气体尺度高度。相反，如果允许垂直剪切不稳定在将灰尘引入我们的模拟之前饱和，则它仍然是灰尘层中湍流的主要来源。垂直剪切不稳定性诱导湍流，其马赫数为$ {\ sim} 10^{ - 1} $，从而阻碍了灰尘沉积。尽管如此，我们发现垂直剪切不稳定性和组合流的不稳定性，从而导致长寿命积累的径向尘埃浓度，这比单独流动不稳定性形成的垂直脱位量显着浓密。因此，垂直的剪切不稳定性可以通过产生弱的过度繁殖来促进行星形成，从而充当流媒体不稳定性的种子。
The streaming instability is a leading candidate mechanism to explain the formation of planetesimals. Yet, the role of this instability in the driving of turbulence in protoplanetary disks, given its fundamental nature as a linear hydrodynamical instability, has so far not been investigated in detail. We study the turbulence that is induced by the streaming instability as well as its interaction with the vertical shear instability. For this purpose, we employ the FLASH Code to conduct two-dimensional axisymmetric global disk simulations spanning radii from $1$ au to $100$ au, including the mutual drag between gas and dust as well as the radial and vertical stellar gravity. If the streaming instability and the vertical shear instability start their growth at the same time, we find the turbulence in the dust mid-plane layer to be primarily driven by the streaming instability. It gives rise to vertical gas motions with a Mach number of up to ${\sim}10^{-2}$. The dust scale height is set in a self-regulatory manner to about $1\%$ of the gas scale height. In contrast, if the vertical shear instability is allowed to saturate before the dust is introduced into our simulations, then it continues to be the main source of the turbulence in the dust layer. The vertical shear instability induces turbulence with a Mach number of ${\sim}10^{-1}$ and thus impedes dust sedimentation. Nonetheless, we find the vertical shear instability and the streaming instability in combination to lead to radial dust concentration in long-lived accumulations which are significantly denser than those formed by the streaming instability alone. Thus, the vertical shear instability may promote planetesimal formation by creating weak overdensities that act as seeds for the streaming instability.
