Monday, 15 April 2019
Dr Jonathan Squire
Department of Physics
"Resonant Drag Instabilities and the fluid dynamics of planet formation"
Astrophysical dust is thought to govern a wide variety of processes, from planet and star formation, to winds from massive stars and galaxies. In all such processes, dust and the ambient gas interact through drag and/or Lorentz forces, presenting an interesting problem in fluid dynamics that will be the focus of my talk. Bulk movement between the two phases – for instance, due to thermal pressure gradients or radiation – can drive the fast-growing "Resonant Drag Instability" (RDI), which is unstable whenever the relative dust-gas streaming velocity matches the phase speed of a fluid wave. As it grows nonlinearly, the RDI drives turbulence in the gas, strongly clumping the dust. This physics is of particular interest for the problem of planetesimal formation: how dust coagulates in protoplanetary disks to form self-gravitating planetesimals. In addition to elucidating the physics of the well-studied "streaming instability" – thought to be key for coagulating cm-sized grains – the RDI formalism reveals a number of other related instabilities. Most interestingly, the "settling instability" is a promising mechanism for coagulating smaller grains at lower densities than the streaming instability, providing a possible path for dust to grow from the micron scale up to kilometre-sized bodies where gravity can take over.
WHEN: Monday 15 April 2019
WHERE: Room 314, Science 3 Building
TIME: 3.00 pm–4.00 pm
All interested are welcome to attend
Light refreshments to follow in Common Room