Aggregate model of cometary dust: an application to comet Levy 1990XX

Das, Himadri Sekhar; Das, Sudeep; Paul, Thomas; Suklabaidya, A.; Sen, A. K.

doi:10.1111/j.1365-2966.2008.13569.x

Cited by 21 publications

(44 citation statements)

References 39 publications

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“…The fractal dimension and the porosity are therefore independent parameters, both characterizing the morphology of fractal aggregates. In order to calculate the porosity of the aggregates, we applied the method by Mukai et al (1992), already used by several other authors (e.g Kozasa et al 1992;Petrova et al 2004;Kimura et al 2006;Bertini et al 2007;Das et al 2008). Firstly, although fractals do not possess a constant internal density, the so-called characteristic radius, R c , is calculated.…”

Section: The Porositymentioning

confidence: 99%

“…A widely-used parameter to describe the effect of volume-filling factor in fractal structures, and irregular particles in general, is the porosity, p, defined as 1 − V/V t , where V is the volume of the solid part of the particle and V t is the total volume, generally intended as the volume of the solid part plus the pores (e.g Greenberg & Hage 1990;Mukai et al 1992;Kozasa et al 1992;Davidsson & Skorov 2002;Petrova et al 2004;Kimura et al 2006;Bertini et al 2007;Das et al 2008;Voshchinnikov & Henning 2008). It should be emphasized at this point that the porosity and the fractal dimension need not to be uniquely related.…”

Section: The Porositymentioning

confidence: 99%

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The influence of the monomer shape in the first stage of dust growth in the protoplanetary disk

Bertini

Gutiérrez

Sabolo

2009

A&A

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Context. Laboratory experiments have shown that the initial stage of the dust growth in the protoplanetary disk starts with low-velocity hit-and-stick collisions between sub-micron grains, before the relative impact energy becomes large enough to cause the morphological restructuring of the forming aggregates. The results of these collisions are loose aggregates characterized by fractal dimensions ≤2. Numerical studies generally model this early stage with colliding clusters made of monodisperse spherical monomers. Aims. In this paper we aimed to investigate how a more complex representation of the monodisperse monomers structure influences the morphology of the final aggregate particles in terms of fractal dimension, porosity, cross-section, and friction time. This study had also the purpose of testing the validity of the current fractal models in representing irregular particles. Methods. We used three kinds of hit-and-stick aggregation methods: two particle-cluster aggregations producing compact and extremely loose aggregates, respectively, and simplified cluster-cluster aggregation as intermediate class in terms of fluffyness and porosity. In our measures, we used two kinds of monomer shapes: spheres and elongated prolate ellipsoids with axis ratio 3:1 resembling the ones used to model interstellar dust grains. Results. We found that the monomer shape has little influence ( 2%) on the fractal dimension of the final aggregate, once large particles are taken into account, independently on the morphological class. Elongated monomers produce structures with larger fractal dimension in the limit of small particles. For loose objects the influence on the porosity is even smaller, whereas elongated monomers give particles with ∼5% higher porosity in the case of large compact fractals. Regardless the ellipsoidal monomer used has, by construction, a cross-section ∼26% larger than the one of the volume-equivalent sphere, the difference in cross-section per unit mass is decreasing when aggregates are considered. Clusters made by elliptical monomers result much coupled to the surrounding gas than objects made by spherical monomers belonging to the same morphological class. Differences in the friction time are estimated to be below 15%. We conclude that the monomer shape influence on the morphology of the final particles during the hit-and-stick aggregation step is much lower than the differences due to considering different morphological classes in modeling and the uncertainties produced in a realistic accretion scenario, where a wide distribution of morphologies is expected. Present models of irregular particles as fractals made by spherical monomers can therefore also represent well more complex shapes, before the restructuring phase is taken into account.

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Section: The Porositymentioning

confidence: 99%

Section: The Porositymentioning

confidence: 99%

The influence of the monomer shape in the first stage of dust growth in the protoplanetary disk

Bertini

Gutiérrez

Sabolo

2009

A&A

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“…The results of in situ measurements carried out on the Giotto spacecraft at Comet Halley (Fulle et al 2000) and the analysis of the infrared spectra of Comet Hale-Bopp (Moreno et al 2003) also agree with the model of aggregates. It is clear from recent modeling of optical (Xing & Hanner 1997;Kimura 2001;Kimura et al 2006;Petrova et al 2004;Tishkovets et al 2004;Lasue et al 2006;Kolokolova et al 2007;Bertini et al 2007;Levasseur-Regourd et al 2007, 2008Das et al 2008a;2008b etc. ), thermal-infrared observations (Lisse et al 1998;Harker et al 2002), laboratory studies (Wurm & Blum 1998;Gustafson & Kolokolova 1999;Hadamcik et al 2002 etc.…”

Section: Introductionmentioning

confidence: 99%

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

Das

Suklabaidya

Majumder

et al. 2010

Res. Astron. Astrophys.

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In our present study, the observed linear polarization data of comet Hyakutake are studied at wavelengths λ = 0.365µm, λ = 0.485µm and 0.684µm through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate aggregates of 128 spherical monomers. We first investigated that the size parameter of the monomer, x ∼ 1.56 -1.70, turned out to be most suitable which provides the best fits to the observed dust scattering properties at three wavelengths λ = 0.365µm, 0.485µm and 0.684µm. Thus the effective radius of the aggregate (r) lies in the range 0.45µm ≤ r ≤ 0.49µm at λ = 0.365µm; 0.60µm ≤ r ≤ 0.66µm at λ = 0.485µm and 0.88µm ≤ r ≤ 0.94µm at λ = 0.684µm. 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 which can best fit 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 coming out from the present analysis correspond to mixture of both silicates and organics, which are in good agreement with the in situ measurement of comets by different spacecraft.

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“…al [49], using JaSTA. We have studied the influence of monomer size on the linear polarization of amorphous olivine by varying the monomer size a m from 0.11 to 0.13 with an interval of 0.01.…”

Section: Variation In Monomer Sizementioning

confidence: 99%

“…Each particle is assumed to consist of a single material, such as silicates or carbon, as formed in the various separate sources of cosmic dust. To study natural aggregates, several investigators [35], [36], [22], [21], [49], [50], [41], [42], [39] etc. built aggregates using ballistic aggregation procedure [51], [52].…”

Section: Aggregate Dust Modelmentioning

confidence: 99%

Java application for the superposition T-matrix code to study the optical properties of cosmic dust aggregates

Halder¹,

Chakraborty²,

Roy³

et al. 2014

Computer Physics Communications

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In this paper, we report the development of a java application for the Superposition T-matrix code, JaSTA (Java Superposition Tmatrix App), to study the light scattering properties of aggregate structures. It has been developed using Netbeans 7.1.2, which is a java integrated development environment (IDE). The JaSTA uses double precession superposition codes for multi-sphere clusters in random orientation developed by Mackowski & Mischenko (1996). It consists of a graphical user interface (GUI) in the front hand and a database of related data in the back hand. Both the interactive GUI and database package directly enable a user to model by self-monitoring respective input parameters (namely, wavelength, complex refractive indices, grain size, etc.) to study the related optical properties of cosmic dust (namely, extinction, polarization, etc.) instantly, i.e., with zero computational time. This increases the efficiency of the user. The database of JaSTA is now created for a few sets of input parameters with a plan to create a large database in future. This application also has an option where users can compile and run the scattering code directly for aggregates in GUI environment. The JaSTA aims to provide convenient and quicker data analysis of the optical properties which can be used in different fields like planetary science, atmospheric science, nano science, etc. The current version of this software is developed for the Linux and Windows platform to study the light scattering properties of small aggregates which will be extended for larger aggregates using parallel codes in future. Program Summary:Program title: JaSTA: Java Superposition T-matrix App. Catalogue identifier: AETB v1 0 Program summary URL:

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Aggregate model of cometary dust: an application to comet Levy 1990XX

Cited by 21 publications

References 39 publications

The influence of the monomer shape in the first stage of dust growth in the protoplanetary disk

The influence of the monomer shape in the first stage of dust growth in the protoplanetary disk

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

Java application for the superposition T-matrix code to study the optical properties of cosmic dust aggregates

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