论文标题
具有多种灰尘物种的流式不稳定性：I。线性生长的有利条件
Streaming Instability with Multiple Dust Species: I. Favourable Conditions for the Linear Growth
论文作者
论文摘要
最近的研究表明，流媒体不稳定性是推动行星模拟形成的主要机制之一，可能不如先前想象的那么有效。在某些圆盘条件下，考虑到多个灰尘物种时，不稳定性的生长时间尺度可能比椎间盘寿命更长。为了进一步探索这一发现，我们使用线性分析和直接的数值模拟使用气体流体和灰尘颗粒来更详细地对不稳定模式相互验证和研究不稳定的模式。我们将先前研究的参数空间延长了一个数量级，在灰尘分布的范围内$ [t_ {s，min}，t_ {s，max}] $和总固体与气体质量比$ \ varepsilon $，并引入了第三个维度，并带有大小分布的斜率$ q $。我们发现，快速增长的制度和慢增长制度在$ \ varepsilon $ - $ t_ {s，max} $ space中明显分开，而此边界对$ q $或$ q $或$ t_ {s，min} $并不明显敏感。圆盘中存在各种灰尘尺寸（例如$ t_ {s，min} \ Lessim10^{ - 3} $），由于考虑了更多的灰尘物种，慢增长状态的增长率会降低。另一方面，由于灰尘尺寸狭窄（例如$ t_ {s，max}/t_ {s，min} = 5 $），另一方面，大多数$ \ varepsilon $ - $ t_ {s，max} $空间的增长率随着尘埃增加而增加，但速度越来越快，但缓慢的增长状态仍然保持分离。此外，最大的灰尘物种没有必要主导不稳定模式的生长，而较小的灰尘物种会以复杂的方式影响生长速度。无论如何，我们发现快速增长制度受$ \ varepsilon \ gtrsim 1 $或$ t_ {s，max} \ gtrsim 1 $界定，这可能代表了行星形成的有利条件。
Recent study suggests that the streaming instability, one of the leading mechanisms for driving the formation of planetesimals, may not be as efficient as previously thought. Under some disc conditions, the growth timescale of the instability can be longer than the disc lifetime when multiple dust species are considered. To further explore this finding, we use both linear analysis and direct numerical simulations with gas fluid and dust particles to mutually validate and study the unstable modes of the instability in more detail. We extend the previously studied parameter space by one order of magnitude in both the range of the dust-size distribution $[T_{s,min}, T_{s,max}]$ and the total solid-to-gas mass ratio $\varepsilon$ and introduce a third dimension with the slope $q$ of the size distribution. We find that the fast-growth regime and the slow-growth regime are distinctly separated in the $\varepsilon$-$T_{s,max}$ space, while this boundary is not appreciably sensitive to $q$ or $T_{s,min}$. With a wide range of dust sizes present in the disc (e.g. $T_{s,min}\lesssim10^{-3}$), the growth rate in the slow-growth regime decreases as more dust species are considered. With a narrow range of dust sizes (e.g. $T_{s,max}/T_{s,min}=5$), on the other hand, the growth rate in most of the $\varepsilon$-$T_{s,max}$ space is converged with increasing dust species, but the fast and the slow growth regimes remain clearly separated. Moreover, it is not necessary that the largest dust species dominate the growth of the unstable modes, and the smaller dust species can affect the growth rate in a complicated way. In any case, we find that the fast-growth regime is bounded by $\varepsilon\gtrsim 1$ or $T_{s,max}\gtrsim 1$, which may represent the favourable conditions for planetesimal formation.
