BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Some instabilities resulting from the existence of the negative en
 ergy modes in a gas-dust disc - Viacheslav Zhuravlev - Sternberg Astronomi
 cal Institute
DTSTART:20210301T140000Z
DTEND:20210301T150000Z
UID:TALK154123@talks.cam.ac.uk
CONTACT:Cleo Loi
DESCRIPTION:The Lagrangian approach can be employed to the dynamics of the
  linear perturbations of gas-dust mixture in protoplanetary disc with the 
 dust streaming through the gas.\nIt shows that gas-dust perturbations may 
 have negative energy provided that there is a bulk settling of dust to the
  disc midplane. The most simple variant of the negative energy gas-dust mo
 de is constructed of the dust density perturbations\ntransported by the bu
 lk stream of dust though the unperturbed gas environment. This mode is ref
 erred to as the streaming dust wave (SDW). SDW coupled with the positive e
 nergy inertial wave (IW) in the gas gives rise to the recently discovered 
 dust settling instability (DSI). Further\, SDW by itself exhibits exponent
 ial growth as gas-dust dynamics becomes dissipative in the presence of tur
 bulence and provided that the effective turbulent viscosity exceeds the ef
 fective turbulent diffusion. This new instability can be referred to as a 
 viscous settling instability (VSI). As compared to DSI\, VSI is produced b
 y modes with larger wavelengths\, while it vanishes in laminar disc and su
 rvives up to the largest value of the effective viscosity in turbulent dis
 c.\n        \n\nAdditionally\, it can be shown that the three-wave resonan
 ce is possible between one negative energy SDW and two positive energy IW'
 s. A particular case of such a resonance is considered in detail in order 
 to show that it gives rise to the non-linear explosive settling instabilit
 y (ESI)\nwith a physically reasonable time of explosion.  DSI\, VSI and ES
 I may serve as early mechanisms for generation of the dust overdensities i
 n the long-standing problem of planetesimal formation.
LOCATION:Online
END:VEVENT
END:VCALENDAR