The effect of porosity of dust particles on polarization and color with
  special reference to comets
  Cosmic dusts are mostly responsible for polarization of the light that we ob-
serve from astrophysical objects. They also lead to color-extinction, thermal
re- emission and other scattering related phenomena. Dusts are made of small
particles which are characterised by their size (radius), composition (matter),
and structure (morphology, including porosity). In the present work, we address
the question of the role of the dust particle porosity on light polarization
and color, using Discrete Dipole Approximation (DDA) light scattering code. To
answer this question, we developed an algorithm to generate solid particles of
arbitrary values of porosity. In brief, the model considers a given homogeneous
structure made of touching dipoles. The dipoles are randomly removed one by
one, such that the remaining structure remains connected. We stop the removal
process when the desired poros- ity is obtained. Then we study the optical
properties of the porous particle. That way, we show how the proper value of
the porosity affects the polarization and color of the light scattered by these
porous particles. In addition to polarization, porosity has important effects
on photometric color. Considering an important application, we emphasize the
possible role of the porosity of the cometary dust particles on polarization
and color of the light scattered by cometary coma.
