Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-09-19
Astron.Astrophys. 429 (2005) 371-381
Astronomy and Astrophysics
Astrophysics
12 pages, 16 figures, Astronomy & Astrophysics (accepted)
Scientific paper
10.1051/0004-6361:200400081
There are indications that interstellar and interplanetary dust grains have an inhomogeneous and fluffy structure. We investigate different methods to describe light scattering by such composite particles. Both a model of layered particles and discrete dipole calculations for particles with Rayleigh and non-Rayleigh inclusions are used. The calculations demonstrate that porosity is a key parameter for determining light scattering. We find that the optical properties of the layered particles depend on the number and position of layers if the number of layers is small ($\la 15$). For a larger number of layers the scattering characteristics become independent of the layer sequence. The optical properties of particles with inclusions depend on the size of inclusions provided the porosity is large. The scattering characteristics of very porous particles with inclusions of different sizes are found to be close to those of multi-layered spheres. We compare the results of these calculations with the predictions of the effective medium theories (EMT) which are often used in astronomy as a tool to calculate the optical properties of composite particles. The results of our analysis show that the internal structure of grains (layers versus inclusions) only slightly affects the optics of particles provided the porosity does not exceed 50%. It is also demonstrated that in this case the optical properties of composite grains calculated with EMT agree with the results of the exact method for layered particles. For larger porosity, the standard EMT rules (i.e., Garnett and Bruggeman rules) give reliable results for particles with Rayleigh inclusions only.
Henning Th
Il'in Vladimir B.
Voshchinnikov Nikolai V.
No associations
LandOfFree
Modelling the optical properties of composite and porous interstellar grains does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Modelling the optical properties of composite and porous interstellar grains, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Modelling the optical properties of composite and porous interstellar grains will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-633687