Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.astro.spbu.ru/staff/ilin2/INTAS/P3-SPB1/CONF/ABSTR/fip-opc2.txt Дата изменения: Fri Nov 19 16:17:32 2010 Дата индексирования: Tue Oct 2 06:20:15 2012 Кодировка: Поисковые слова: molecular cloud

Light scattering by multi-layered ellipsoidal particles
in quasi-static approximation

V.G.Farafonov
St.Petersburg University of Aerocosmic Instrumentation
St.Petersburg, 190000, Russia

and

V.B.Il'in
Astronomical Institute, St.Petersburg University
St.Petersburg, 198504, Russia


ABSTRACT

Calculation of light scattering by finite size non-axisymmetric inhomogeneous
particles is a complicated problem whose solution by the exact methods (e.g.,
the Discrete Dipole Approximation) is very computational time consuming.
Therefore any approximate solution of the problem for multi-layered
ellipsoidal particles is of interest.

A recent review on approximate approaches presented in [1] describes the
current state of the Rayleigh, Rayleigh-Gans, anomalous diffraction and
other approximations for homogeneous and core/mantle particles.
The Rayleigh approximation for multi-layered confocal and non-confocal
ellipsoids was developed in [2,3] only after the appearance of the book [1].

A not sufficient space in the review was devoted to the quasi-static
approximation being a generalization of the Rayleigh and Rayleigh-Gans
approximations, when the field inside a homogeneous particle is represented
by the incident field similarly to the Rayleigh-Gans approximation,
taking into account the particle polarizability like in the Rayleigh
approximation (see [4-7] for more details). For multi-layered particles,
the polarizability is calculated in a special way using the Rayleigh
approximation [6].

It should be emphasized that the quasi-static approximation has an
essentially wider range of applicability than the Rayleigh and Rayleigh-Gans
approximations [5-6]. The approximation works in particular efficiently
in the case of strongly elongated or flattened particles [6-7]. For
homogeneous spheroids, the quasi-static approximation was shown to give
the main term of the asymptotics of scattered radiation in the limit of
small values of the aspect ration of the particles [7] (see also [8-9]
for more details).

In this paper we consider light scattering by multi-layered (non-confocal)
ellipsoidal and spheroidal particles in the quasi-static approximation.
Some results obtained for ensembles of such particles are presented as well.

The work was partly supported by INTAS (grant 99/652).


References:

1. Mishchenko M.I., Hovenier J.W., Travis L.D. (2000) Light Scattering by
Non-Spherical Particles, Acad. Press.
2. Farafonov V.G. (2000) Opt. Spectr. 88, 441.
3. Farafonov V.G. (2000) Opt. Spectr. in press.
4. Farafonov V.G. (1994) Opt. Spectr. 77, 402.
5. Voshchinnikov N.V., Farafonov V.G. (2000) Opt. Spectr. 88, 71.
6. Farafonov V.G., Prokopjeva M.S., Il'in V.B., Henning Th. (2000)
in: W.L.Smith and Yu.M.Timofeyev (eds.) IRS 2000: Current Problems in
Atmospheric Radiation, A.Deepack Publ., Hampton, VA.
7. Voshchinnikov N.V., Farafonov V.G. (1993) Astrophys. Space Sci. 204, 19.
8. Farafonov V.G. (1989) Opt. Spectr. 66, 86.
9. Farafonov V.G. (1990) Opt. Spectr. 68, 232.