Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

Stark, C.R. and Diver, D.A. (2018) Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering. Astronomy and Astrophysics, 611, A91. (doi: 10.1051/0004-6361/201731253)

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Abstract

Context. In contemporary sub-stellar model atmospheres, dust growth occurs through neutral gas-phase surface chemistry. Recently, there has been a growing body of theoretical and observational evidence suggesting that ionisation processes can also occur. As a result, atmospheres are populated by regions composed of plasma, gas and dust, and the consequent influence of plasma processes on dust evolution is enhanced. Aim. This paper aims to introduce a new model of dust growth and destruction in sub-stellar atmospheres via plasma deposition and plasma sputtering. Methods. Using example sub-stellar atmospheres from DRIFT-PHOENIX, we have compared plasma deposition and sputtering timescales to those from neutral gas-phase surface chemistry to ascertain their regimes of influence. We calculated the plasma sputtering yield and discuss the circumstances where plasma sputtering dominates over deposition. Results. Within the highest dust density cloud regions, plasma deposition and sputtering dominates over neutral gas-phase surface chemistry if the degree of ionisation is ≳10−4. Loosely bound grains with surface binding energies of the order of 0.1–1 eV are susceptible to destruction through plasma sputtering for feasible degrees of ionisation and electron temperatures; whereas, strong crystalline grains with binding energies of the order 10 eV are resistant to sputtering. Conclusions. The mathematical framework outlined sets the foundation for the inclusion of plasma deposition and plasma sputtering in global dust cloud formation models of sub-stellar atmospheres.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Stark, Mr Craig and Diver, Professor Declan
Authors: Stark, C.R., and Diver, D.A.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN:0004-6361
ISSN (Online):1432-0746
Published Online:06 April 2018
Copyright Holders:Copyright © 2018 ESO
First Published:First published in Astronomy and Astrophysics 611: A91
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172170Evolution and dynamics of pellets and dust in dynamic gas-plasma systemsDeclan DiverEngineering and Physical Sciences Research Council (EPSRC)EP/N018117/1P&S - Physics & Astronomy