摘要：Context. Large-scale vortices could play a key role in the evolution of
protoplanetary disks, particularly in the dead-zone where no turbulence associated with
magnetic field is expected. Their possible formation by the subcritical baroclinic
instability is a complex issue because of the vertical structure of the disk and the
elliptical instability.
Aims. In 2D disks the baroclinic instability is studied as a function of
the thermal transfer efficiency. In 3D disks we explore the importance of radial and
vertical stratification on the processes of vortex formation and amplification.
Methods. Numerical simulations are performed using a fully compressible
hydrodynamical code based on a second-order finite volume method. We assume a perfect gas
law in inviscid disk models in which heat transfer is due to either relaxation or
diffusion.
Results. In 2D, the baroclinic instability with thermal relaxation leads
to the formation of large-scale vortices, which are unstable with respect to the elliptic
instability. In the presence of heat diffusion, hollow vortices are formed which evolve
into vortical structures with a turbulent core. In 3D, the disk stratification is found to
be unstable in a finite layer which can include the mid-plane or not. When the unstable
layer contains the mid-plane, the 3D baroclinic instability with thermal relaxation is
found to develop first in the unstable layer as in 2D, producing large-scale vortices.
These vortices are then stretched out in the stable layer, creating long-lived columnar
vortical structures extending through the width of the disk. They are also found to be the
source of internal vortex layers that develop across the whole disk along baroclinic
critical layer surfaces, and form new vortices in the upper region of the disk.
Conclusions. In 3D disks, vortices can survive for a very long time if
the production of vorticity by the baroclinic amplification balances the destruction of
vorticity by the elliptical instability. However, this possibility is strongly dependent
on the disk properties. Such baroclinic vortices could play a significant role in the
global disk evolution and in participating to the decoupling of solids from the gas
component. They could also contribute to the formation of new out-of-plane vortices by a
critical layer excitation mechanism.
