BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:The physical mechanism of the streaming instability\, and whether 
 it works in vortices - Nathan Magnan (DAMTP)
DTSTART:20240423T120000Z
DTEND:20240423T130000Z
UID:TALK213646@talks.cam.ac.uk
CONTACT:Dr Dolev Bashi
DESCRIPTION:A major hurdle in planet formation theory is that we do not un
 derstand how small pebbles congregate into big planetesimals. A promising 
 way to overcome this metre-scale barrier involves a fluid dynamics phenome
 non called the streaming instability (SI). It concentrates the pebbles int
 o clumps that are dense enough to collapse gravitationally\, thereby formi
 ng planetesimals.\n\nUnfortunately\, the mechanism responsible for the ons
 et of the instability remains mysterious. This makes it hard to evaluate t
 he robustness of the instability\, or to understand how it saturates. It h
 as recently been shown that the SI is a Resonant Drag Instability (RDI) in
 volving inertial waves. In the first part of this talk\, I build on this i
 nsight to produce a clear physical picture of how the SI develops.\n\nAnot
 her problem is that the SI can only devellop in regions containing a high 
 density of similar-sized pebbles. Those conditions are met in large-scale 
 vortices\, but no one knows if the SI can feed on vorticial flows. Indeed\
 , any instability can only devellop in specific flows\, and a priori the S
 I is tailored to Keplerian disc flows\, not vortex flows. I answer this qu
 estion in the second part of the talk. To do so\, I develop a simple pen-a
 nd-paper model of a dust-laden vortex in a protoplanetary disc. I find tha
 t if the vortex is weak and anticyclonic\, dust drifts towards its centre.
  I then build a vortex analog of the shearing box to analyse the local lin
 ear stability of my dusty vortex. I find that the dust’s drift powers an
  instability which closely resembles the SI. This result strengthens the c
 ase for vortex-induced planetesimal formation.
LOCATION:Hoyle Committee Room + ONLINE - Details to be sent by email
END:VEVENT
END:VCALENDAR