Effect of the dust grain size-distribution on the nonlinear dispersion relation for parametric instabilities in dusty plasmas

2001 ◽  
Vol 8 (11) ◽  
pp. 5040-5042 ◽  
Author(s):  
M. Ishak Boushaki ◽  
R. Annou ◽  
B. Ferhat
Keyword(s):  
Grain Size ◽  
Dispersion Relation ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Dusty Plasmas ◽  
Nonlinear Dispersion ◽  
Nonlinear Dispersion Relation ◽  
Parametric Instabilities ◽  
Dust Grain

scholarly journals Chemical modelling of dust–gas chemistry within AGB outflows – II. Effect of the dust-grain size distribution

2020 ◽  
Vol 495 (2) ◽  
pp. 1650-1665 ◽  
Author(s):  
M Van de Sande ◽  
C Walsh ◽  
T Danilovich
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Gas Phase ◽  
Surface Area ◽  
Grain Size Distribution ◽  
Agb Stars ◽  
Gas Chemistry ◽  
Starting Point ◽  
Dust Grain ◽  
Grain Surface

ABSTRACT Asymptotic giant branch (AGB) stars are, together with supernovae, the main contributors of stellar dust to the interstellar medium (ISM). Dust grains formed by AGB stars are thought to be large. However, as dust nucleation and growth within their outflows are still not understood, the dust-grain size distribution (GSD) is unknown. This is an important uncertainty regarding our knowledge of the chemical and physical history of interstellar dust, as AGB dust forms ${\sim} 70{{\ \rm per\ cent}}$ of the starting point of its evolution. We expand on our chemical kinetics model, which uniquely includes a comprehensive dust–gas chemistry. The GSD is now allowed to deviate from the commonly assumed canonical Mathis, Rumpl & Nordsieck distribution. We find that the specific GSD can significantly influence the dust–gas chemistry within the outflow. Our results show that the level of depletion of gas-phase species depends on the average grain surface area of the GSD. Gas-phase abundance profiles and their possible depletions can be retrieved from observations of molecular emission lines when using a range of transitions. Because of degeneracies within the prescription of GSD, specific parameters cannot be retrieved, only (a lower limit to) the average grain surface area. None the less, this can discriminate between dust composed of predominantly large or small grains. We show that when combined with other observables such as the spectral energy distribution and polarized light, depletion levels from molecular gas-phase abundance profiles can constrain the elusive GSD of the dust delivered to the ISM by AGB outflows.

Parametric instabilities with well separated frequencies in magnetized plasmas

1981 ◽  
Vol 25 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Yu-Mei Chou ◽  
Shih-Tung Tsai
Keyword(s):  
Dispersion Relation ◽  
Ponderomotive Force ◽  
Dipole Approximation ◽  
Magnetized Plasma ◽  
Nonlinear Dispersion ◽  
Anomalous Absorption ◽  
Force Method ◽  
Nonlinear Dispersion Relation ◽  
Parametric Instabilities ◽  
The Right

A nonlinear dispersion relation is derived for a homogeneous, magnetized plasma by the conventional ‘ponderomotive force’ method. By using this dispersion relation, various parametric instabilities (stimulated anomalous absorptions and scatterings) are discussed. The results are compared in detail with those obtained by other authors. In the validity region of this model the results derived by previous authors can be recovered. In addition to obtaining a few instabilities which have not been published in the literature, we also find that in general (i) the ‘dipole approximation’ can give the right results for the stimulated anomalous absorption problems and (ii) the ambient magnetic field may enhance the plasma stability.

scholarly journals Evolution of grain size distribution in galactic discs

2020 ◽  
Vol 636 ◽  
pp. A18 ◽  
Author(s):  
M. Relaño ◽  
U. Lisenfeld ◽  
K.-C. Hou ◽  
I. De Looze ◽  
J. M. Vílchez ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Radial Distribution ◽  
Molecular Gas ◽  
Evolutionary Stage ◽  
Dust Grains ◽  
Cosmological Simulations ◽  
Dust Grain ◽  
Dust Evolution

Context. Dust is formed out of stellar material and it is constantly affected by different mechanisms occurring in the interstellar medium. Depending on their size, the behaviour of dust grains vary under these mechanisms and, therefore, the dust grain size distribution evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that has only recently become the subject of consideration. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy, together with cosmological simulations, are producing the first predictions of the evolution of dust grain size distribution. Aims. We compare, for the first time, the evolution of the dust grain size distribution as predicted by SPH simulations and results from observations. We are able to validate not only the predictions of the evolution of the small-to-large grain mass ratio (DS/DL) within a galaxy, but we also provide observational constraints for recent cosmological simulations that include the grain size distribution in the dust evolution framework. Methods. We selected a sample of three spiral galaxies with different masses: M 101, NGC 628, and M 33. We fitted the dust spectral energy distribution across the disc of each object and derived the abundance of the different grain types included in the dust model. We analysed how the radial distribution of the relative abundance of the different grain size populations changes over the whole disc within each galaxy. The DS/DL ratio as a function of the galactocentric distance and metallicity is directly compared to what has been predicted by the SPH simulations. Results. We find a good agreement between the observed radial distribution of DS/DL and what was obtained from the SPH simulations of a single galaxy. The comparison agrees with the expected evolutionary stage of each galaxy. We show that the central parts of NGC 628 at a high metallicity and with a high molecular gas fraction are mainly affected not only by accretion, but also by the coagulation of dust grains. The centre of M 33, having a lower metallicity and lower molecular gas fraction, presents an increase in the DS/DL ratio, demonstrating that shattering is very effective for creating a large fraction of small grains. Finally, the observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two-grain size approximation. However, we also present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies.

A Model for the Changing Pore Structure and Dust Grain Size Distribution in a Porous Comet Nucleus

Icarus ◽  
1997 ◽  
Vol 126 (2) ◽  
pp. 342-350 ◽  
Author(s):  
Yossi Shoshani ◽  
Eyal Heifetz ◽  
Dina Prialnik ◽  
Morris Podolak
Keyword(s):  
Grain Size ◽  
Pore Structure ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Comet Nucleus ◽  
Dust Grain
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