TERRAPUB Earth, Planets and Space
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Earth Planets Space, Vol. 65 (No. 3), pp. 139-148, 2013
doi:10.5047/eps.2012.02.003

Light scattering by cometary dust: Large-particle contribution

Evgenij Zubko1,2

1Department of Physics, P.O. Box 64, FIN-00014, University of Helsinki, Finland
2Astronomical Institute of Kharkov National University, 35 Sumskaya St., Kharkov, 61022, Ukraine

(Received January 11, 2012; Revised February 12, 2012; Accepted February 13, 2012; Online published March 12, 2013)

Abstract: Using the discrete dipole approximation (DDA) and a model of agglomerated debris particles, we study the contribution of large particles on the light scattering by cometary dust. The numerical simulations show that moderately and highly absorbing particles larger than 3 μm do not significantly affect the backscattering phenomena observed at visible wavelengths in comets at phase angles α ≤ 30°, such as the brightness surge and the negative polarization branch. Weakly and non-absorbing particles may play some role even if they are larger than 3 μm; but they are not abundant species in comets. However, the contribution of large particles on polarizations at phase angles α>30° can be significant, even though they are highly absorbing; simultaneously, the phase dependence of brightness remains insensitive to the contribution of large particles.
Key words: Comets, backscattering, enhancement of brightness, negative polarization, discrete dipole approximation.


Corresponding author E-mail: ezubko@rambler.ru


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