Dust in brown dwarfs

I. Dust formation under turbulent conditions on microscopic scales

¹ Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
² Konrad-Zuse-Zenrum für Informationstechnik Berlin, Takustraße 7, 14195 Berlin, Germany
³ Fachbereich Mathematik und Informatik, Freie Universität Berlin, Takustraße 7, 14195 Berlin, Germany

Corresponding author: Ch. Helling, chris@astro.physik.tu-berlin.de

Received: 3 May 2001
Accepted: 27 June 2001

Abstract

Dust formation in turbulent media is studied adopting the example of brown dwarf atmospheres. By combining asymptotic techniques and time-dependent, multi-dimensional numerical simulations, we show that acoustic waves originating from convective motions provide a mechanism to initiate dust nucleation in otherwise dust-hostile environments. The subsequently growing particles cause a radiative cooling strong enough to re-initiate efficient dust formation resulting in a strongly inhomogeneous distribution of dust in such environments. Recent observations bear indications for such cloudy dust distributions in brown dwarf atmospheres.