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Issue A&A
Volume 448, Number 1, March II 2006
Page(s) 395 - 399
Section Planets and planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20053332



A&A 448, 395-399 (2006)
DOI: 10.1051/0004-6361:20053332

Applicability of the discrete-dipole approximation to light-scattering simulations of large cosmic dust aggregates

M. Köhler1, H. Kimura2 and I. Mann1

1  Institut für Planetologie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
    e-mail: koehlert@uni-muenster.de
2  Institute of Low Temperature Science, Hokkaido University, Kita-ku Kita-19 Nishi-8, Sapporo 060-0819, Japan

(Received 28 April 2005 / Accepted 11 October 2005 )

Abstract
Light-scattering properties of cosmic dust particles depend on the structure and composition of the particles. A common model assumption of cosmic dust particles that is consistent with observational data is to describe them as aggregates consisting of irregularly shaped, inhomogeneous, submicron-sized monomers. It is necessary for a study of their optical properties to apply a proper light-scattering theory, in which we can fully take this shape and structure of particles into account. Among currently available light-scattering theories, the discrete-dipole approximation (DDA) with the lattice dispersion relation (LDR) is the best method to simulate light scattering by aggregates of such complex structures. We investigate the accuracy of the LDR-DDA method with large aggregates consisting of spherically shaped, homogeneous, identical monomers of 0.1 $\mu$m in radius, for which rigorous solutions are known. The asymmetry parameter and single-scattering albedo of these aggregates are here computed with the LDR-DDA method as well as the superposition T-matrix method. We find that the conditions previously given in the literature to calculate cross sections of spherical particles within the accuracy of a few percent are also suitable for large aggregates. We discuss the required computer memory that restricts simulating the optical properties of the considered aggregates.


Key words: scattering -- solar system: general -- circumstellar matter -- dust, extinction -- meteors, meteoroids




© ESO 2006


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