Light scattering by multi-layered ellipsoidal particles
                 in the quasistatic approximation

          B Posselt^1,2, V G Farafonov^3, V B Il'in^2
                     and M S Prokopjeva^2

   ^1 Friedrich Schiller University, Schillergaesschen 2-3,
      Jena, D-07745 Germany

   ^2 Sobolev Astronomical Institute,St.Petersburg University,
      Bibliotechnaya pl.2, St.Petersburg 198504, Russia

   ^3 St.Petersburg University of Aerocosmic Instrumentation,
      Bol.Morskaya 67, St.Petersburg 190000, Russia


                           Abstract

The Rayleigh (RA) and Rayleigh-Gans (RGA) approximations are generalized
in the form of the quasistatic approximation (QSA).
The advantage of the QSA is most conspicuous
for non-spherical scatterers. In that case,
the RA, RGA, etc. are known to have the applicability range quickly
decreasing with a growing particle asphericity, whereas
the range of the QSA remains practically independent of the scatterer
shape.

In this paper we develop the QSA for multi-layered ellipsoids
in the general case of non-confocal layer surfaces. In principle,
the approach used should give a solution for ellipsoidal particles
with any internal structure of this kind.

Our numerical results for multi-layered ellipsoids
show that the QSA is preferable to the RA (and RGA)
if the ratio of the maximum to minimum dimensions of
the outer (inner) boundary of the layer dominating the scattering process
exceeds $\sim$3, which well coincides with the conclusion
drawn earlier for homogeneous spheroids.

We also introduce a special rule of the effective medium theory
giving much more accurate results than the known ones
for small layered ellipsoids.