Aggregate dust model to study the polarization properties of comet C/1996 B2 Hyakutake  

作　　者：Himadri Sekhar Das Abinash Suklabaidya Saonli Datta Majumder Asoke Kumar Sen 

机构地区：[1]Department of Physics,Assam University

出　　处：《Research in Astronomy and Astrophysics》2010年第4期355-362,共8页天文和天体物理学研究（英文版）

摘　　要：The observed linear polarization data of comet Hyakutake are studied at wavelengths λ=0.365 μm,λ=0.485 μm and 0.684μm through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate aggregates of 128 spherical monomers.We first found that the size parameter of the monomer,x ～ 1.56-1.70,turned out to be the most suitable which provides the best fits to the observed dust scattering properties at three wavelengths：λ=0.365 μm,0.485μm and 0.684μm.Thus,the effective radius of the aggregate （r） lies in the range 0.45 μm ≤ r ≤ 0.49 μm at λ=0.365 μm;0.60 μm ≤ r ≤ 0.66 μm at λ=0.485 μm and 0.88 μm ≤ r ≤ 0.94 μm at λ=0.684 μm.Now using superposition T-MATRIX code and the power-law size distribution,n（r） ～ r-3,the best-fitting values of complex refractive indices are calculated for the observed polarization data at the above three wavelengths.The best-fitting complex refractive indices （n,k） are found to be （1.745,0.095） at λ=0.365 μm,（1.743,0.100） at λ=0.485 μm and （1.695,0.100） at λ=0.684 μm.The refractive indices derived from the present analysis correspond to a mixture of both silicates and organics,which are in good agreement with the in situ measurement of comets by different spacecraft.The observed linear polarization data of comet Hyakutake are studied at wavelengths λ=0.365 μm,λ=0.485 μm and 0.684μm through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate aggregates of 128 spherical monomers.We first found that the size parameter of the monomer,x ～ 1.56-1.70,turned out to be the most suitable which provides the best fits to the observed dust scattering properties at three wavelengths：λ=0.365 μm,0.485μm and 0.684μm.Thus,the effective radius of the aggregate （r） lies in the range 0.45 μm ≤ r ≤ 0.49 μm at λ=0.365 μm;0.60 μm ≤ r ≤ 0.66 μm at λ=0.485 μm and 0.88 μm ≤ r ≤ 0.94 μm at λ=0.684 μm.Now using superposition T-MATRIX code and the power-law size distribution,n（r） ～ r-3,the best-fitting values of complex refractive indices are calculated for the observed polarization data at the above three wavelengths.The best-fitting complex refractive indices （n,k） are found to be （1.745,0.095） at λ=0.365 μm,（1.743,0.100） at λ=0.485 μm and （1.695,0.100） at λ=0.684 μm.The refractive indices derived from the present analysis correspond to a mixture of both silicates and organics,which are in good agreement with the in situ measurement of comets by different spacecraft.

关 键 词：comets：general - dust extinction - scattering - polarization 

分 类 号：P185.81[天文地球—天文学] TN253[电子电信—物理电子学]