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SUMMARY:Intermittency in the interstellar medium - Dr. Pierre Lesaffre (LE
 RMA - ENS)
DTSTART:20150602T120000Z
DTEND:20150602T130000Z
UID:TALK58579@talks.cam.ac.uk
CONTACT:Jean Teyssandier
DESCRIPTION:Regardless of the mechanisms which stir the interstellar gas\,
  the damping of its turbulent motions must occur at much smaller scales\, 
 where microscopic dissipative processes such as viscous friction\, Ohmic r
 esistivity or ambipolar diffusion can take place. The resulting heating is
  therefore likely to be extremely localised and intense\, thus highly susc
 eptible to open new chemical routes. The chemical species produced in the 
 wake of such hot spots should therefore help us to study observationnally 
 the turbulent dissipation mechanisms in the interstellar gas.\n\nWe first 
 present 3D magnetohydrodynamic simulations (with ambipolar diffusion) of d
 ecaying turbulence in which we extract the structures of high dissipation.
  We show that these structures are highly coherent and that their geometri
 cal properties obey remarkable statistical scalings. We present attempts a
 t characterizing their location in the plane of the sky through maps of ce
 ntroid line velocities or polarisation angle increments.\n\nWe then examin
 e small scale 2D hydrodynamic simulations (with chemistry) of decaying tur
 bulence. In this 2D set up\, highly dissipative structures are along ridge
 s and we observe a strong molecular enhancement in their wake. We fit stea
 dy-shocks locally to these structures and we examine the statistics of the
 ir entrance parameters. We finally examine how much these shocks can accou
 nt for the average chemical abundances in our simulations\, to estimate wh
 en other forms of dissipation (such as shearing sheets / vortices) are nee
 ded or not.\n\n\n\n\n\nReferences\n\n[1] Momferratos G.\, Lesaffre P.\, Fa
 lgarone E.\, Pineau des Forêts G. (2014)\, MNRAS\, 443\, 86\n[2] Falgaron
 e E.\, Momferratos G.\, Lesaffre P. (2014)\, in "Magnetic Fields in Diffus
 e Media"\, eds. E. de Gouveia Dal Pino\, A. Lazarian\, C. Melioli\, Spring
 er.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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