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SUMMARY:Instabilities and the remarkable survivability of AGN jets. - Serg
 uei Komissarov (Leeds)
DTSTART:20250224T140000Z
DTEND:20250224T150000Z
UID:TALK227659@talks.cam.ac.uk
CONTACT:Thomas Jannaud
DESCRIPTION:Jets powered by active galactic nuclei (AGN) appear impressive
 ly stable in comparison to their terrestrial and laboratory counterparts -
  they can be traced from their origin to distances exceeding their injecti
 on radius by up to a billion times.  However some of them\, the Fanaroff-R
 iley class I (FR-I) jets in particular\, get disrupted and lose their cohe
 rence on the scale of host galaxy.  It has been suggested that the surviva
 bility of AGN jets is related to their rapid expansion\, and that the inst
 abilities develop only when they eventually become confined/recollimated b
 y the surrounding plasma.  \n \nMotivated by this hypothesis\, we carried 
 out 3D computer simulations of jets propagating through plasma with rapidl
 y declining pressure and jets recollimated by galactic coronas with flat p
 ressure distribution. The results support the stabilising role of jet expa
 nsion and show that the recollimation of unmagnetized jets by external pre
 ssure is indeed accompanied by a rapid development of instability and tran
 sition to a turbulent state.  This instability is driven by the inertial f
 orce associated with the curved streamlines of recollimated jets and hence
  relates to the well-known centrifugal instability. Simulations of magneti
 sed jets show that even relatively weak azimuthal magnetic field can suppr
 ess the recollimation instability\, with the critical relativistic magneti
 sation parameter sigma about 0.01. These results are consistent with our h
 euristic analysis of the relativistic centrifugal instability (CFI) and th
 e computer simulations of relativistic rotating fluids. 
LOCATION:MR14 DAMTP and online
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