Disk Weather

Baroclinic Instability and Vortex Amplification

¹ Max-Planck Institute für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
² Jet Propulsion Laboratory - California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109, USA

^a e-mail: klahr@mpia.de
^b e-mail: raettig@mpia.de
^c e-mail: Wladimir.Lyra@jpl.nasa.gov

Abstract

Recent years have shown that accretion disks around young stars have extended regions, which are too low ionized to couple to magnetic fields and thus the nature of the underlying turbulence cannot be exclusively magnetic. We also found that disks have in general a baroclinic density and temperature structure which means that a typical disk is radially buoyant and has a vertical velocity gradient also known as thermal wind. Here we show that the expected entropy gradients in observed accretion disks around young stars are in fact steep enough and that the thermal relaxation times are sufficiently short to allow for efficient amplification of vortices.