部分电离原行星盘的新复合模型
New composite models of partially ionized protoplanetary disks
摘要：
我们研究了一个吸积盘，其中三个不同的区域可能共存：MHD湍流区，死区和引力不稳定区。虽然死区是稳定的，但由于与从湍流层发射的波相关的雷诺应力，存在一些传输。我们在每个不同的区域通过其自己的$α$参数，这是10到$10^{3}$倍小死区比在活动层的运输模型。在引力不稳定区域，$α$是由圆盘自我调整到边缘稳定状态的事实决定的。我们构建这样的磁盘的稳态模型。我们发现，对于均匀的质量流，盘必须更大的质量，更热，更厚的半径有一个死区。在死区质量很大的圆盘中，存在引力不稳定性。这种模型是否真实，取决于湍流层驱动的流体动力学波动是否能一直穿透死区。当活性层的质量与死区的质量的比率相对较大时，这可以更容易地实现，在我们的模型中，这对应于死区中的$α$为活性层中的$α$的约10%。如果圆盘在其演化的某个阶段不是处于稳态，那么表面密度将向稳态解演化。然而，如果死区中的$α$比活动区中的小得多，则磁盘的超出几个AU的部分达到稳定状态的时间尺度可能变得比磁盘寿命长。具有死区的稳态盘比标准盘更有利于行星形成，因为死区的质量通常比相同位置的相应湍流区大10倍。
英文摘要：
We study an accretion disk in which three different regions may coexist: MHD turbulent regions, dead zones and gravitationally unstable regions. Although the dead zones are stable, there is some transport due to the Reynolds stress associated with waves emitted from the turbulent layers. We model the transport in each of the different regions by its own $α$ parameter, this being 10 to $10^{3}$ times smaller in dead zones than in active layers. In gravitationally unstable regions, $α$ is determined by the fact that the disk self-adjusts to a state of marginal stability. We construct steady-state models of such disks. We find that for uniform mass flow, the disk has to be more massive, hotter and thicker at the radii where there is a dead zone. In disks in which the dead zone is very massive, gravitational instabilities are present. Whether such models are realistic or not depends on whether hydrodynamical fluctuations driven by the turbulent layers can penetrate all the way inside the dead zone. This may be more easily achieved when the ratio of the mass of the active layer to that of the dead zone is relatively large, which in our models corresponds to $α$ in the dead zone being about 10% of $α$ in the active layers. If the disk is at some stage of its evolution not in steady-state, then the surface density will evolve toward the steady-state solution. However, if $α$ in the dead zone is much smaller than in the active zone, the timescale for the parts of the disk beyond a few AU to reach steady-state may become longer than the disk lifetime. Steady-state disks with dead zones are a more favorable environment for planet formation than standard disks, since the dead zone is typically 10 times more massive than a corresponding turbulent zone at the same location.
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