Light Scattering by Interplanetary Fractal Aggregates

行星际分形聚集体的光散射

• 批准号: 04835011
• 负责人: MUKAI Tadashi
• 金额: $ 1.22万
• 依托单位: Kobe University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1993
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04835011/
• 关键词: Solar system; Interplanetary dust grains; Fractal; Light scattering

(1)Fractal aggregate model has been applied to the irregularly shaped dust particles existing in the interplanetary space. Their scattering properties have been examined in detail. In 1992, a wavelength dependence of their absorption/pressure coefficients has been deduced and in 1993 a phase angle dependence of their scattering function has been obtained. It is found from these works that Discrete Dipole Approximation is useful method to estimate the scattering properties of fractal aggregates. Furthermore we have learned that there exists an applicable limit on the conventional method called as Maxwell-Garnett Mie theory.(2)A motion of interplanetary dust can be estimated from the analysis of doppler shifts measured in the zodiacal light. In the previous investigation one famous question has been left, namely why the velocity of grain deduced from Doppler shifts is larger than Kepler velocity inside the Earth's orbit. We have re-examined the theoretical formula of velocity-dependence of observed Doppler shifts and found a lack of important factor in that estimation. Our revised formula has solved the long standing problem and consequently it has predicted a variation of the nature of dust grains with a solar distance.Referring to the scattering pattern of irregularly shaped particles considered above, the observed polarimetric data of 4179 Toutatis, which is one of near-Earth asteroids, have been examined. It is found that the Toutatis would be covered by inhomogeneous rough surface with regolith.

(1)将分形聚集模型应用于存在于行星际空间的不规则形状尘埃粒子。对它们的散射特性进行了详细的研究。1992年推导出它们的吸收/压力系数与波长的关系，1993年推导出它们的散射函数与相角的关系。这些工作表明离散偶极近似是估计分形聚集体散射特性的有效方法。此外，我们还了解到，传统的称为麦克斯韦-加内特米氏理论的方法存在一个适用的极限。(2)通过分析黄道光测量的多普勒频移，可以估计行星际尘埃的运动。在之前的研究中留下了一个著名的问题，即为什么从多普勒频移推断出的颗粒速度大于地球轨道内的开普勒速度。我们重新检验了观测到的多普勒频移与速度相关的理论公式，发现在该估计中缺少一个重要因素。我们修正的公式解决了长期存在的问题，因此它预测了尘埃颗粒性质随太阳距离的变化。参考上述不规则形状粒子的散射模式，对近地小行星之一的4179 Toutatis的观测偏振数据进行了研究。研究发现，图塔蒂斯将被不均匀的粗糙表面和风化层所覆盖。

项目成果

I.Mann, H.Okamoto, T.Mukai, H.Kimura and Y.Kitada: "Fractal aggregate and analogues for near solar dust properties" Astron.Astrophys. (submitted). (1994)

I.Mann、H.Okamoto、T.Mukai、H.Kimura 和 Y.Kitada：“近太阳尘埃特性的分形聚合和类似物”Astron.Astrophys。

T.Watanabe: "Polarization distribution of the inner cometary coma" Proc.of the 26th ISAS Lunar and Planetary Symp. 13-16 (1993)

T.Watanabe：“内部彗星彗差的偏振分布”Proc.of the 26th ISAS Lunar and Planetary Symp。

Tadashi Mukai: "Fragmentation of Fluffy Dust Particles" Proc.of International Astro.Symp.“Meteoroids and Theu Parent Bodies". (1993)

Tadashi Mukai：“蓬松尘埃粒子的碎片”Proc.of International Astro.Symp.“流星体和 Theu 母体”(1993)。

T.Mukai: Sho-wakusei ga yatte kuru(Japanese). Iwanami Syoten, (1994)

T.Mukai：Sho-wakusei ga yatte kuru（日语）。

T.Mukai: "Polarimetry of asteroids" Planetary and Space Science. (印刷中). (1994)

T.Mukai：“小行星的偏振测量”，行星与空间科学（正在出版）（1994 年）。