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Anders Johansen. Profile picture.

Anders Johansen


Anders Johansen. Profile picture.

Diffusion and Concentration of Solids in the Dead Zone of a Protoplanetary Disk


  • Chao Chin Yang
  • Mordecai Mark Mac Low
  • Anders Johansen

Summary, in English

The streaming instability is a promising mechanism to drive the formation of planetesimals in protoplanetary disks. To trigger this process, it has been argued that sedimentation of solids onto the mid-plane needs to be efficient, and therefore that a quiescent gaseous environment is required. It is often suggested that dead-zone or disk-wind structure created by non-ideal magnetohydrodynamical (MHD) effects meets this requirement. However, simulations have shown that the mid-plane of a dead zone is not completely quiescent. In order to examine the concentration of solids in such an environment, we use the local-shearing-box approximation to simulate a particlegas system with an Ohmic dead zone including mutual drag force between the gas and the solids. We systematically compare the evolution of the system with ideal or non-ideal MHD, with or without backreaction drag force from particles on gas, and with varying solid abundances. Similar to previous investigations of deadzone dynamics, we find that particles of dimensionless stopping time ts = 0.1 do not sediment appreciably more than those in ideal magnetorotational turbulence, resulting in a vertical scale height an order of magnitude larger than in a laminar disk. Contrary to the expectation that this should curb the formation of planetesimals, we nevertheless find that strong clumping of solids still occurs in the dead zone when solid abundances are similar to the critical value for a laminar environment. This can be explained by the weak radial diffusion of particles near the mid-plane. The results imply that the sedimentation of particles to the mid-plane is not a necessary criterion for the formation of planetesimals by the streaming instability.


  • Lund Observatory
  • eSSENCE: The e-Science Collaboration

Publishing year





Astrophysical Journal





Document type

Journal article


American Astronomical Society


  • Astronomy, Astrophysics and Cosmology


  • instabilities
  • magnetohydrodynamics (MHD)
  • methods: numerical
  • planets and satellites: formation
  • protoplanetary disks
  • turbulence




  • ISSN: 0004-637X