Umov effect for single-scattering agglomerate particles E. Zubko , 1,2 G. Videen, 3 Yu. Shkuratov, 2 K. Muinonen, 1,4 and T. Yamamoto 5 May 8, 2012 1 Department of Physics, University of Helsinki, Finland 2 Institute of Astronomy, Kharkov National University, Ukraine 3 Army Research Laboratory AMSRL-CI-EM, USA 4 Finnish Geodetic Institute, Finland 5 Institute of Low Temperature Science, Hokkaido University, Japan
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Umov effect for single-scattering agglomerate particles
Umov effect for single-scattering agglomerate particles. E. Zubko , 1,2 G. Videen, 3 Yu. Shkuratov, 2 K. Muinonen, 1,4 and T. Yamamoto 5. 1 Department of Physics, University of Helsinki, Finland 2 Institute of Astronomy, Kharkov National University, Ukraine - PowerPoint PPT Presentation
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Umov effect for single-scattering agglomerate particles
E. Zubko,1,2 G. Videen,3 Yu. Shkuratov,2
K. Muinonen,1,4 and T. Yamamoto5
May 8, 2012
1 Department of Physics, University of Helsinki, Finland2 Institute of Astronomy, Kharkov National University, Ukraine3 Army Research Laboratory AMSRL-CI-EM, USA4 Finnish Geodetic Institute, Finland5 Institute of Low Temperature Science, Hokkaido University, Japan
Polarimetry of Comets
Circumstances of polarimetric observations
Dependence of polarization in comets on
phase angle
The brighter powder, the lower its linear polarization
N. Umov (1846-1915)
N. Umov, Phys. Zeits. 6, 674-676 (1905)
In 1960-1970, the qualitative law was quantified:
log(Pmax) linearly depends on log(A)
Origin of the phenomenon – depolarization due to multiple scattering in regolith
Umov Effect
Shkuratov & Opanasenko, Icarus 99, 468-484 (1992)
Umov Effect
Geometric albedo A for single particles:
A=(S11(0))/(k2G)
Here, S11(0) is the Mueller matrix element at back-scattering, k – wavenumber, and G – the geometric cross-section of the particle.
Umov Effect for Single-Scattering ParticlesAs was found in Zubko et al. (2011, Icarus, 212,
403– 415), the Umov effect holds also for single-scattering particles with size comparable to wavelength. Therefore, it can be applied to comets.
Basic idea:
Gains: (1) arbitrary shape and internal structure (2) simplicity in preparation of sample
1.5+0.021.5+0.02ii – – Inner coma Inner coma 0.2310.231
Application to innermost coma in 26P/Grigg-Skjellerup
Using the Umov effect, one can estimate albedo of single-scattering dust particles.
When this technique is applied to whole Comet C/1996 B2 (Hyakutake), it yields the geometric albedo in the range A=0.034–0.079, that is well consistent with the expected value of A=0.05.
For the innermost coma studied by Giotto in 26P/Grigg-Skjellerup, the Umov effect reveals dramatically higher geometric albedo A=0.23.