原行星盘天生就有旋涡吗？--由原恒星坠落驱动的Rossby波不稳定性
Are protoplanetary disks born with vortices? -- Rossby wave instability driven by protostellar infall
摘要：
我们进行了双流体，二维全球流体动力学模拟，以测试是否原恒星落入可以触发Rossby波不稳定性（RWI）在原行星盘。我们的研究结果表明，降落可以触发的RWI和产生的涡旋附近的质量降落在磁盘的外缘（即离心半径）。我们发现，RWI是在各种条件下触发的，虽然细节取决于磁盘参数和下落模式。触发RWI的共同关键特征是由下落区域外边缘的局部密度增加引起的方位角速度的陡峭径向梯度。当不稳定性进入非线性区域时，旋涡形成。在我们的标准模型中，自引力被忽略，旋涡在$\sim 20$局部轨道时间内合并成单个旋涡，合并的旋涡在计算的剩余时间（$> 170$局部轨道时间）内存活。旋涡参与向外的角动量输送，雷诺应力为$\lesssim10^{-2}$。我们的双流体计算表明，涡旋有效地捕获尘埃粒子的轨道时间的顺序的停止时间，局部提高适当大小的颗粒的灰尘气体比的一个因素，$\sim 40$在我们的标准模型。然而，当考虑自重力时，涡流往往会受到阻碍而无法合并，最终可能会消散。我们的结论是，很可能有原行星盘有良好的条件，在原恒星的下降阶段，这可能会促进早期行星核心的形成。
英文摘要：
We carry out two-fluid, two-dimensional global hydrodynamic simulations to test whether protostellar infall can trigger Rossby wave instability (RWI) in protoplanetry disks. Our results show that infall can trigger the RWI and generate vortices near the outer edge of the mass landing on the disk (i.e. centrifugal radius). We find that the RWI is triggered under a variety of conditions, although the details depend on the disk parameters and the infall pattern. The common key feature of triggering the RWI is the steep radial gradient of the azimuthal velocity induced by the local increase in density at the outer edge of the infall region. Vortices form when the instability enters the nonlinear regime. In our standard model where self-gravity is neglected, vortices merge together to a single vortex within $\sim 20$ local orbital times, and the merged vortex survives for the remaining duration of the calculation ($> 170$ local orbital times). The vortex takes part in outward angular momentum transport, with a Reynolds stress of $\lesssim10^{-2}$. Our two-fluid calculations show that vortices efficiently trap dust particles with stopping times of the order of the orbital time, locally enhancing the dust to gas ratio for particles of the appropriate size by a factor of $\sim 40$ in our standard model. When self-gravity is considered, however, vortices tend to be impeded from merging and may eventually dissipate. We conclude it may well have that protoplanetary disks have favorable conditions for vortex formation during the protostellar infall phase, which might enhance early planetary core formation.
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