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Physical properties of heterogeneous dust grain

异质尘粒的物理性质

基本信息

批准号：
60540163
负责人：
MUKAI Tadashi
金额：
$ 1.28万
依托单位：
Kanazawa Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60540163/
关键词：
Solar system Comets Cometary dust Interplanetary dust 塵の物理特性

项目摘要

Exploration of Comet Halley has provided many valuable information of the cometary dust grains. Then, it becomes possible to do more qualitative analysis concerning the origin and evolution of dust in the solar system. Based on the heterogeneous grain model, the following topics were examined.(1) The complex refractive index <m^*> of heterogeneous material measured for mixtures of <H_2> O/ and <NH_3> ices are compared with those estimated based on the Maxwell-Garnett mixing rule. We found that when there are no newly formed chemical bonds between ice and inclusions, the MG rule can give the reasonable values of <m^*> for heterogeneous material.(2) Dirty ice attains higher temperature than pute ice does. This result preferrs to explain higher production rate of OH molecules in a distant comet.(3) Since a lifetime of dirty water-ice grain ejected from the cometary nucleus is short, we can't expect the detection of large halo of icy particles around the nucleus when comet enters to the comet-sun distance less than 1 AU.(4) Dirty ice grains look 'dark' in distant place from the sun. Time evolution of these dark grains causes brighter particles because loss of <H_2> O due to sublimation leads refractory grains with high albedos. Therefore, it can explain the observed evidence that the grains located far from the sun have lower albedos compared with those near the sun.It is found that our heterogeneous grain model is a powerful tool to analyse the observed results in comets, as well as in interplanetary space.

哈雷彗星的探测提供了许多有价值的彗星尘埃信息。这样，就有可能对太阳系中尘埃的起源和演化进行更多的定性分析。基于非均匀晶粒模型，研究了以下问题。(1)测量的混合物的O/和冰的非均质材料的复折射率<m^*><H_2><NH_3>进行了比较的基础上的麦克斯韦-加内特混合规则的估计。我们发现，当冰和包裹体之间没有新形成的化学键时，MG规则可以给出非均质材料的<m^*>的合理值。(2)脏冰比普通冰达到更高的温度。这一结果更倾向于解释遥远彗星中OH分子的较高产生率。(3)由于从彗核喷出的脏水-冰粒的寿命很短，当彗星进入到彗星-太阳距离小于1 Au时，我们不能期望探测到彗核周围的大的冰粒晕。(4)肮脏的冰粒在离太阳较远的地方看起来很“暗”。这些暗颗粒的时间演化导致较亮的颗粒，因为<H_2>由于升华导致的O损失导致具有高折射率的难熔颗粒。因此，它可以解释观测到的证据，即远离太阳的颗粒比那些靠近太阳的颗粒具有较低的折射率。我们发现，我们的非均匀颗粒模型是一个强大的工具来分析在彗星，以及在行星际空间的观测结果。