1993 Fiscal Year Final Research Report Summary
Light Scattering by Interplanetary Fractal Aggregates
| Project/Area Number |
04835011
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
惑星科学
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| Research Institution | Kobe University |
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Principal Investigator |
MUKAI Tadashi Faculty of Science, Professor, 理学部, 教授 (10097412)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Solar system / Interplanetary dust grains / Fractal / Light scattering |
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| Research Abstract |
(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.
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