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Astrophysics Colloquium

The Origin of Vortices and Rings in Disks around Young Stars
Presented by Hubert Klahr
Max Planck Institute for Astronomy, Heidelberg

Thursday, November 14, 2019
11:00 A.M. in 169-336

Abstract
"Rings" in disks, which are called "zonal flows" in atmospheric physics, as well as vortices are typical features in any rotating weakly turbulent system - just look at the Earth weather and jet-stream system or the bands and vortices on Jupiter and Saturn.

Yet, our concept of viscously evolving accretion disks around young stars has established the common presumption that disks if left alone should be axis-symmetric and characterized by monotonic falling power-laws in the radial mass distribution. In fact if a viscous process evolves a disk, then all perturbations disappear and a monotonic radial density distribution is established. Therefore, an observed ring or vortex in a disk seems to need continuous forcing by a perturber, for instance a planet. Thus, planets are observers' favorite explanation for rings and vortices, and whereas planets with a certain mass do lead to gaps, the inverse conclusion should be handled with care.

For A: one needs rings and vortices to facilitate important steps in the building of a planet, like planetesimal formation, thus it would be great if rings and vortices can predate planets.

And B: one has to recognize zonal flows and vortices as a common feature in a spinning gas disk, rather characterizing the rotational profile and Mach number of the disk than pinpointing to a specific perturber, distinguishing between planet or weak turbulence.

In this talk I summarize our current understanding how these non-laminar flow features can arise in weakly turbulent disks do to a plethora of magneto and radiation hydro dynamical instabilities.

So not all rings are signs for already present planets, but they show us that planets are in the making.

JPL Contact: Karen Willacy (4-3467)


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