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Streaming instabilities in vortices

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If you have a question about this talk, please contact Callum William Fairbairn.

First year report seminar

Vortices, as non-axisymmetric dust traps, are a popular option to bridge the meter gap of planet formation. In particular, vortices are thought to concentrate dust to the point where the streaming instability (SI) becomes viable. But the SI is a disk instability, and it is not known whether it is active in vortices. In the first half of the talk, I investigate this question from the analytical front, by building a model for dusty vortices and studying its linear stability. I find that dusty vortices are unstable, and that the instability is a resonant drag instability (RDI), similar in some regards to the SI. My new instability offers a way to interpret simulations of dusty vortices, and strengthens the case for vortex-catalysed planet formation.

In the second half of the talk, I build a simple physical picture for RDIs, in particular the SI. I find that RDIs are built on two familiar mechanisms: In the first one, a gas wave concentrates dust. In the second one, a drifting dust clump excites gas waves. These mechanisms are usually transient and independent of each other, but at resonance they both become algebraically unstable, and they start feeding into each other. My model closes a long discussion on the mechanism behind the SI, and provides a solid footing upon which to base future RDI investigations.

This talk is part of the DAMTP Astro Mondays series.

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