The need for small-scale turbulence in atmospheres of substellar objects

Original · EN

Brown dwarfs and giant gas planets are substellar objects whose spectral appearance is determined by the chemical composition of the gas and the solids/liquids in the atmosphere. Atmospheres of substellar objects possess two major scale regimes: large-scale convective motions + gravitational settling and small-scale turbulence + dust formation. Turbulence initiates dust formation spot-like on small scale, while the dust feeds back into the turbulent fluid field by its strong radiative cooling. Small, imploding dust containing areas result which eventually become isothermal. Multi-dimensional simulations show that these small-scale dust structures gather into large-scale structures, suggesting the formation of clouds made of dirty dust grains. The chemical composition of the grains, and thereby the chemical evolution of the gas phase, is a function of temperature and depends on the grain's history.