Planetary nurseries: vortices formed at smooth viscosity transition

ABSTRACT Excitation of Rossby wave instability and development a large-scale vortex at the outer dead zone edge protoplanetary discs is one leading theories that explains horseshoe-like brightness distribution in transition discs. Formation such vortices requires relatively sharp viscosity transition. Detailed modelling, however, indicates transitions smooth. In this study, we present 2D global, non-isothermal, gas–dust coupled hydrodynamic simulations to investigate possibility excitation smooth transitions. Our models are based on recently postulated scenario, wherein recombination charged particles surface dust grains results reduced ionization fraction and, turn, turbulence due magnetorotational instability. Thus, α-parameter for disc depends local dust-to-gas mass ratio. We found can become unstable form vortices. A single develops if content well gas; multiple small-scale ensue case less dust. As both type trapped edge, they provide sufficient time growth. The solid collected by exceed several hundred Earth masses, while density ratio within often exceeds unity. function as planetary nurseries disc, providing ideal sites formation planetesimals eventually systems.