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Dust in Brown Dwarfs IV. Dust formation and driven turbulence on mesoscopic scales

Please always quote using this URN: urn:nbn:de:0297-zib-7555
  • Dust formation {in brown dwarf atmospheres} is studied by utilizing a model for driven turbulence in the mesoscopic scale regime. We apply a pseudo-spectral method where waves are created and superimposed {within} a {limited} wavenumber interval. The turbulent kinetic energy distribution follows the Kolmogoroff spectrum which is assumed to be the most likely value. Such superimposed, stochastic waves may occur in a convectively active environment. They cause nucleation fronts and nucleation events and thereby initiate the dust formation process which { continues until} all condensible material is consumed. Small disturbances {are found to} have a large impact on the dust forming system. An initially dust-hostile region, which may originally be optically thin, becomes optically thick in a patchy way showing considerable variations in the dust properties during the formation process. The dust appears in lanes and curls as a result of the interaction with waves, i.e. turbulence, which form larger and larger structures with time. Aiming on a physical understanding of the variability of brown dwarfs, related to structure formation in substellar atmospheres, we work out first necessary criteria for small-scale closure models to be applied in macroscopic simulations of dust forming astrophysical systems.

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Metadaten
Author:Christiane Helling, Rupert Klein, Peter Woitke, Ulrich Nowak, Erwin Sedlmayr
Document Type:ZIB-Report
Tag:dust formation; substellar atmospheres; turbulence
MSC-Classification:76-XX FLUID MECHANICS (For general continuum mechanics, see 74Axx, or other parts of 74-XX) / 76Fxx Turbulence [See also 37-XX, 60Gxx, 60Jxx] / 76F65 Direct numerical and large eddy simulation of turbulence
76-XX FLUID MECHANICS (For general continuum mechanics, see 74Axx, or other parts of 74-XX) / 76Pxx Rarefied gas flows, Boltzmann equation [See also 82B40, 82C40, 82D05] / 76P05 Rarefied gas flows, Boltzmann equation [See also 82B40, 82C40, 82D05]
85-XX ASTRONOMY AND ASTROPHYSICS (For celestial mechanics, see 70F15) / 85-08 Computational methods
85-XX ASTRONOMY AND ASTROPHYSICS (For celestial mechanics, see 70F15) / 85Axx Astronomy and astrophysics (For celestial mechanics, see 70F15) / 85A20 Planetary atmospheres
85-XX ASTRONOMY AND ASTROPHYSICS (For celestial mechanics, see 70F15) / 85Axx Astronomy and astrophysics (For celestial mechanics, see 70F15) / 85A30 Hydrodynamic and hydromagnetic problems [See also 76Y05]
CCS-Classification:J. Computer Applications / J.2 PHYSICAL SCIENCES AND ENGINEERING
PACS-Classification:90.00.00 GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS (for more detailed headings, see the Geophysics Appendix) / 95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations / 95.30.-k Fundamental aspects of astrophysics (see also section 26 Nuclear astrophysics) / 95.30.Lz Hydrodynamics
90.00.00 GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS (for more detailed headings, see the Geophysics Appendix) / 95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations / 95.30.-k Fundamental aspects of astrophysics (see also section 26 Nuclear astrophysics) / 95.30.Tg Thermodynamic processes, conduction, convection, equations of state
90.00.00 GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS (for more detailed headings, see the Geophysics Appendix) / 95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations / 95.30.-k Fundamental aspects of astrophysics (see also section 26 Nuclear astrophysics) / 95.30.Wi Dust processes (condensation, evaporation, sputtering, mantle growth, etc.)
90.00.00 GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS (for more detailed headings, see the Geophysics Appendix) / 97.00.00 Stars (for relativistic stars, see 04.40.Dg in general relativity and gravitation) / 97.82.-j Extrasolar planetary systems / 97.82.Jw Infrared excess; debris disks; protoplanetary disks; exo-zodiacal dust
Date of first Publication:2003/10/30
Series (Serial Number):ZIB-Report (03-33)
ZIB-Reportnumber:03-33
Published in:Appeared in: Astronomy & Astrophysics 423 (2004) 657-675
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