Atmospheric Dynamics of Brown Dwarfs and Directly Imaged Giant Planets

摘要: A variety of observations provide evidence for vigorous motion in the atmospheres brown dwarfs and directly imaged giant planets. Motivated by these observations, we examine dynamical regime circulation interiors objects. Brown rotate rapidly, plausible wind speeds, flow at large scales will be rotationally dominated. We present three-dimensional, global, numerical simulations convection interior, which demonstrate that scales, aligns direction parallel to rotation axis. Convection occurs more efficiently high latitudes than low latitudes, leading systematic equator-to-pole temperature differences may reach ∼1 K near top zone. The interaction with overlying, stably stratified atmosphere generate a wealth atmospheric waves, arguethat,asinthestratospheresofplanetsinthesolarsystem,theinteractionofthesewaveswiththemeanflowwill causeasignificantatmosphericcirculationatregionaltoglobalscales.Atlargescales,thisshouldconsistofstratified turbulence (possibly organizing into coherent structures such as vortices jets) an accompanying overturning circulation. approximate analytic theory this circulation, predicts characteristic horizontal variations several ∼50 K, speeds ∼10‐300 m s −1 , vertical velocities advect air over scale height ∼10 5 ‐10 6 s. This mixing help explain chemical disequilibrium observed on some dwarfs. Moreover, implied large-scale organization perturbations suggests L/T transition, patchy clouds can form photosphere, helping recent brown-dwarf variability near-IR.