光蒸发风中的尘埃输送和卷吸
Dust delivery and entrainment in photoevaporative winds
摘要：
我们对经历极紫外光蒸发的湍流原行星盘中的气体和尘埃动力学进行了建模，以便更好地表征热成风中的尘埃特性（例如尺寸分布、通量率、轨迹）。我们的半分析方法使我们能够快速计算这些灰尘的属性，而无需诉诸昂贵的流体动力学模拟。我们发现，光蒸发创建一个垂直的气流内的光盘，协助湍流提供灰尘的电离前。我们研究了尘埃的电离前，其随后夹带在上覆风的交付。我们推导出一个简单的分析标准，可以夹带的最大晶粒尺寸，并表明，这是在良好的协议与以前的模拟结果，其中光蒸发是由一系列的辐射类型驱动。我们表明，在磁驱动风的情况下，我们不希望大规模的尘埃运输光盘内的光蒸发的影响。我们还表明，可以被风夹带的颗粒的最大尺寸（$s_{\rm max}$）比仅通过平流输送到前方的颗粒的最大尺寸大约大一个数量级（赫比格Ae/Be星的$s_{\rm crit} \lesssim 1$ $μ{\rm m}$和金牛座T星的$\lesssim 0.01$ $μ{\rm m}$）。我们进一步研究如何更大的晶粒，到一个有限的大小$s_{\rm limit}$，可以单独通过湍流扩散传递到前面。在所有的情况下，我们发现$s_{\rm max} \gtrsim s_{\rm limit}$，所以我们预计，任何灰尘，是提供到前面可以被夹带在风中，大多数夹带的灰尘遵循的轨迹接近的气体。
英文摘要：
We model the gas and dust dynamics in a turbulent protoplanetary disc undergoing extreme-UV photoevaporation in order to better characterise the dust properties in thermal winds (e.g. size distribution, flux rate, trajectories). Our semi-analytic approach allows us to rapidly calculate these dust properties without resorting to expensive hydrodynamic simulations. We find that photoevaporation creates a vertical gas flow within the disc that assists turbulence in supplying dust to the ionisation front. We examine both the delivery of dust to the ionisation front and its subsequent entrainment in the overlying wind. We derive a simple analytic criterion for the maximum grain size that can be entrained and show that this is in good agreement with the results of previous simulations where photoevaporation is driven by a range of radiation types. We show that, in contrast to the case for magnetically driven winds, we do not expect large scale dust transport within the disc to be effected by photoevaporation. We also show that the maximum size of grains that can be entrained in the wind ($s_{\rm max}$) is around an order of magnitude larger than the maximum size of grains that can be delivered to the front by advection alone ($s_{\rm crit} \lesssim 1$ $μ{\rm m}$ for Herbig Ae/Be stars and $\lesssim 0.01$ $μ{\rm m}$ for T Tauri stars). We further investigate how larger grains, up to a limiting size $s_{\rm limit}$, can be delivered to the front by turbulent diffusion alone. In all cases, we find $s_{\rm max} \gtrsim s_{\rm limit}$ so that we expect that any dust that is delivered to the front can be entrained in the wind and that most entrained dust follows trajectories close to that of the gas.
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