Turbulence in the ICM from mergers, cool-core sloshing and jets: results
  from a new multi-scale filtering approach
  We have designed a simple multi-scale method that identifies turbulent
motions in hydrodynamical grid simulations. The method does not assmume ant
a-priori coherence scale to distinguish laminar and turbulent flows. Instead,
the local mean velocity field around each cell is reconstructed with a
multi-scale filtering technique, yielding the maximum scale of turbulent eddies
by means of iterations. The method is robust, fast and easily applicable to any
grid simulation. We present here the application of this technique to the study
of spatial and spectral properties of turbulence in the intra cluster medium,
measuring turbulent diffusion and anisotropy of the turbulent velocity field
for a variety of driving mechanisms: a) accretion of matter in galaxy clusters
(simulated with ENZO); b) sloshing motions around cool-cores (simulated with
FLASH); c) jet outflows from active galactic nuclei, AGN (simulated with
FLASH). The turbulent velocities driven by matter accretion in galaxy clusters
are mostly tangential in the inner regions (inside the cluster virial radius)
and isotropic in regions close to the virial radius. The same is found for
turbulence excited by cool core sloshing, while the jet outflowing from AGN
drives mostly radial turbulence motions near its sonic point and beyond.
Turbulence leads to a diffusivity in the range =10^29-10^30 cm^2/s in the intra
cluster medium. On average, the energetically dominant mechanism of turbulence
driving in the intra cluster medium is represented by accretion of matter and
major mergers during clusters evolution.
