Abstract Details

Name: Naznin R Choudhury
Affiliation: Assam University, Silchar, India
Conference ID: ASI2017_1216
Title : Study of porous grains and related properties of cometary dust
Authors and Co-Authors : A. K. Sen Assam University, Silchar, India and R. Botet Laboratoire de Physique des Solides UMR8502, Universit ́e Paris-Sud, Universit ́e Paris-Saclay, Orsay, France
Abstract Type : Oral
Abstract Category : Sun and the Solar System
Abstract : The study of comets gives us valuable information about the least processed and pristine materials of early solar nebula from which the present day solar system has been evolved. The knowledge of the physical properties of cometary dust comes from the study of scattered light or re-emitted thermal radiation from the dust present in the coma of comet. Cometary dusts are fluffy or porous aggregates with irregular shapes. The light scattering and re-emission properties of porous (fractal) dust can be calculated by various numerical codes such as DDA, T-Matrix, etc. In the present study, the optical properties of such porous dusts, with two different models, have been discussed. One model considers a homogeneous structure made of touching dipoles. The dipoles are randomly removed one by one from a compact structure, such that the remaining structure remains connected. The other model generates dusts with porosity by randomly removing dipoles, without constraining the dipoles to remain connected. To study the effect of porosity, the polarization values at different porosities are calculated using DDSCAT light scattering code, the results obtained for both models are compared. In a separate work, the values of effective refractive indices are obtained from effective medium theory assuming the particle is homogeneous. Then, using Mie results, the differences between DDA and EMT has been discused. Also, the thermal re-emission from cometary dust in terms of composition and size distribution has been discussed.