Abstract Details

Name: Prithish Halder
Affiliation: Physical Research Laboratory, Ahmedabad
Conference ID: ASI2021_159
Title : A comet dust model based on the findings from the Rosetta mission.
Authors and Co-Authors : Prithish Halder & Shashikiran Ganesh (Astronomy & Astrophysics Division, Physical Research Laboratory, Ahmedabad)
Abstract Type : Poster
Abstract Category : Sun and the Solar System
Abstract : The morphology of dust particles observed by the Rosetta/MIDAS and COSIMA instruments reveal the presence of fluffy aggregated dust particles having hierarchical structure called Hierarchical Aggregates (HA) with smallest unit or monomer size of 0.1µm (σ = ±0.02 µm to ±0.035µm). In this work we construct HA using Ballistic Cluster Cluster Agglomeration (BCCA) algorithm having mean size of 0.1 µm and polydispersity (σ). We also construct Solids (dust with low porosity) using the algorithm for agglomerated debris (porosity < 10%) and a mixed morphology having mixture of HA and Solids called Fluffy Solids (with moderate porosity). The three morphologies are used as light scattering targets for light scattering simulations using Multi-Sphere T-Matrix (MSTM) and Discrete Dipole Approximation (DDA) codes, considering inhomogeneous mixed composition of silicate minerals and carbonaceous materials having power law size distribution index (n) in the range 2.0 – 3.0. The degree of linear polarization obtained from the light scattering computations over the modelled dust particles allow us to simulate the polarization-phase curve, observed in the case of the comets 1P/Halley, 67P/Churyumov-Gerasimenko, C/1995 O1 Hale-Bopp and C/1996 B2 (Hyakutake). The dust model is verified by the polarimetric color profile which exhibits a positive trend as obtained by previous studies. Also, the model recreates the wavelength dependence of polarization observed in the case of the comet Hale-Bopp. Finally, the model agrees with the idea that long-period comets may have a high percentage of loose particles, retaining the morphology from the proto-planetary phase, while the short-period comets possess a high percentage of solid particles with low porosity. This difference in the dust properties could be due to frequent and/or higher magnitude of weathering by solar radiation during the relatively more frequent passages close to the Sun by the short-period comets. This computational study extensively used the Vikram-100 HPC facility at PRL, Ahmedabad.