标题： 演化星周盘中的颗粒传输： Stardust结果的启示 显示英文标题

标题： Particle transport in evolving protoplanetary disks: Implications for results from Stardust

摘要： 由星尘任务从维尔德2号彗星采集的样本确认，在彗星形成过程中掺入了大量晶体硅酸盐。 我们研究了这一观察结果对原行星盘物理施加的限制，假设在外流过程中，通过高温处理的颗粒向外传输是通过在演化盘中的对流和湍流扩散实现的。 我们也寻找关于颗粒形成位置的限制条件。 我们的结果基于随时间演化的一维盘模型，在粘性作用和光蒸发作用下发生变化，并利用粒子轨迹集合追踪固体传输。 我们发现有两种类型的盘模型与星尘任务的结果一致。 一类具有较高的粒子扩散性（施密特数Sc < 1），这足以使大小达20微米的粒子在平均气流方向上向外扩散。 对于Sc > 1，这类模型不太可能成立，显著的向外传输需要感兴趣的颗粒下沉到经历向外气流的中平面层。 在这两种模型类中，内盘物质到达外盘的质量强烈依赖于盘的初始紧密程度。 因此，稳态盘中的颗粒传输模型低估了向外传输的效率。 这两种模型都不支持非常大的颗粒（超过毫米级）的持续向外传输。 我们表明，传输效率通常会随着时间迅速下降。 因此，高温材料必须迅速被纳入冰质天体以避免回落，显著的径向传输可能仅发生在快速盘演化的初期阶段。 此外，根据它们的初始质量分布情况，不同盘之间的传输也可能存在显著差异。 我们讨论了这些结果对斯皮策望远镜观测T型恒星盘中晶体硅酸盐的意义。 显示英文摘要

摘要： Samples returned from comet 81P/Wild 2 by Stardust confirm that substantial quantities of crystalline silicates were incorporated into the comet at formation. We investigate the constraints that this observation places upon protoplanetary disk physics, assuming that outward transport of particles processed at high temperatures occurs via advection and turbulent diffusion in an evolving disk. We also look for constraints on particle formation locations. Our results are based upon 1D disk models that evolve with time under the action of viscosity and photoevaporation, and track solid transport using an ensemble of individual particle trajectories. We find that two classes of disk model are consistent with the Stardust findings. One class features a high particle diffusivity (a Schmidt number Sc < 1), which suffices to diffuse particles up to 20 microns in size outward against the mean gas flow. For Sc > 1, such models are unlikely to be viable, and significant outward transport requires that the particles of interest settle into a midplane layer that experiences an outward gas flow. In either class of models, the mass of inner disk material that reaches the outer disk is a strong function of the disk's initial compactness. Hence, models of grain transport within steady-state disks underestimate the efficiency of outward transport. Neither model results in sustained outward transport of very large particles exceeding a mm in size. We show that the transport efficiency generally falls off rapidly with time. Hence, high-temperature material must be rapidly incorporated into icy bodies to avoid fallback, and significant radial transport may only occur during the initial phase of rapid disk evolution. It may also vary substantially between disks depending upon their initial mass distributions. We discuss implications for Spitzer observations of crystalline silicates in T Tauri disks.