Joint Astrophysics Colloquium

Special Astrophysics Seminar

Turbulence from the Streaming Instability and Planetesimal Formation

Andrew Youdin

CITA

I will first provide a general overview of theories of planetesimal formation and related observations, experiments, and meteoritic clues. Then I will describe recent work with Anders Johansen on the generation of turbulence in protoplanetary disks via the streaming instability. The streaming instability (Youdin & Goodman 2005) arises from the relative drift of aerodynamically coupled particles and gas, with energy ultimately coming from the global radial pressure gradient. Computer simulations confirm the linear growth rates and show that streaming instabilities spontaneously develop into turbulence. In the saturated state most particles reside in clumps with overdensities up to 100 or greater, despite the absence of self-gravity and presence of diffusive turbulent motions. The relevance of these results for planetesimal formation will be emphasized.