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Physical properties of cometary and interplanetary dust

机译：彗星和行星际尘埃的物理性质

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In the absence of numerous in situ studies, physical properties of cosmic dust may be derived from observations of their light scattering and thermal properties, through numerical simulations making use of realistic assumptions. Estimations about cometary and interplanetary dust composition, structure, size, as well as about their light scattering and thermal properties, are first summarized. We then present and discuss the numerical simulations we have performed with different types of particles: core-mantle submicron-sized elongated grains (having contributed to the formation of cometary dust), fractal aggregates of such grains (found in cometary comae and in the interplanetary dust cloud), and fractal aggregates of large dust grains (found in cometary dust trails). A very satisfactory fit to the numerous polarimetric observations of comet Hale-Bopp is obtained for a mixture with about 33-60% of organics in mass, with a power law size distribution with an index of (-3) and a radius of 20 μm for the upper cut-off. For the less-constrained polarimetric observations of interplanetary dust near 1 AU, a fit is obtained for a mixture with about 40% of organics in mass, with a similar size distribution and a radius of about 50 μm for the upper cut-off. The ensemble of results obtained for the interplanetary dust strongly suggest that its light scattering and thermal properties stem from the presence of compact and fluffy particles, with compositions ranging from silicates to more absorbing materials, whose contribution decreases with decreasing distance to the Sun.
机译：在没有大量原位研究的情况下，宇宙尘埃的物理性质可能是通过使用实际假设进行数值模拟而从其光散射和热性质的观察中得出的。首先总结了有关彗星和行星际尘埃组成，结构，大小以及它们的光散射和热特性的估算。然后，我们介绍并讨论我们对不同类型的粒子执行的数值模拟：核幔套亚微米尺寸的细长晶粒（有助于形成彗星尘埃），此类颗粒的分形聚集体（在彗星彗星和行星际星际中发现）尘云）和大尘粒的分形聚集体（在彗星尘埃痕迹中发现）。对于质量约为33-60％的有机物的混合物，其幂律尺寸分布的指数为（-3），半径为20μm，非常适合海尔-波普彗星的众多极化观测结果用于上边界。对于较少受约束的1 AU附近星际尘埃的极化观测，对于质量约为40％的有机物的混合物，具有相似的尺寸分布，且上边界的半径约为50μm，因此得到了拟合。关于行星际尘埃获得的大量结果强烈表明，它的光散射和热学性质是由于存在致密而蓬松的颗粒而形成的，其组成范围从硅酸盐到吸收更多的材料，其贡献随着距太阳距离的减小而减小。

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