Abstract

The paper considers the free molecular flow of gas through the dusty porous surface layer of a comet nucleus. The study is based on computer models of generation of a porous medium and Knudsen gas diffusion. We consider various types of homogeneous and heterogeneous layers constructed from nonintersecting spheres, including layers that contain microcracks or inner cavities. Using the test-particle method, we quantitatively estimate the free path distribution function, layer permeability, and effective kinetic characteristics of sublimation products passing through a nonisothermal porous layer. In addition, in this approach, we consider the volumetric absorption of visible solar radiation in the near-surface absorbing layer. Simple approximation expressions are obtained for all the transport characteristics under study, which makes it possible to estimate the characteristics with sufficient accuracy for practical applications in the physics of comets. The results will be used to construct new consistent models of energy transfer in the near-surface layer of a comet nucleus and, first of all, to analyze the results of the observations of comet 67P/Churyumov‒Gerasimenko.

中文翻译：

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67P /丘留莫夫-格拉西缅科彗星核近表面层的输运特性

摘要

本文考虑了穿过彗核多尘多孔表面层的气体自由分子流。该研究基于多孔介质生成和Knudsen气体扩散的计算机模型。我们考虑了由不相交的球体构成的各种类型的均质和非均质层，包括包含微裂纹或内腔的层。使用测试粒子方法，我们定量估计了通过非等温多孔层的升华产物的自由程分布函数，层渗透性和有效动力学特性。另外，在这种方法中，我们考虑了近表面吸收层中可见太阳辐射的体积吸收。对于所研究的所有传输特性，都获得了简单的近似表达式，这使得有可能以足够的精度估算出特性，以用于彗星物理学中的实际应用。该结果将用于在彗星核的近表层构造新的一致的能量传输模型，首先，将分析67P / Churyumov‒Gerasimenko彗星的观测结果。