Turbulence decay in the density-stratified intracluster medium

Journal Article · 20 May 2019 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stz1392 · OSTI ID:1523665

Shi, Xun  ^[1]; Zhang, Congyao  ^[2]

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1. South-Western Institute for Astronomy Research (SWIFAR), Yunnan University, 650500 Kunming, P. R. China, Max-Planck-Institut für Astrophysik (MPA), Karl-Schwarzschild-Straße 1, D-85740 Garching bei München, Germany
2. Max-Planck-Institut für Astrophysik (MPA), Karl-Schwarzschild-Straße 1, D-85740 Garching bei München, Germany

Abstract Turbulence evolution in a density-stratified medium differs from that of homogeneous isotropic turbulence described by the Kolmogorov picture. We evaluate the degree of this effect in the intracluster medium (ICM) with hydrodynamical simulations. We find that the buoyancy effect induced by ICM density stratification introduces qualitative changes to the turbulence energy evolution, morphology, and the density fluctuation–turbulence Mach number relation, and likely explains the radial dependence of the ICM turbulence amplitude as found previously in cosmological simulations. A new channel of energy flow between the kinetic and the potential energy is opened up by buoyancy. When the gravitational potential is kept constant with time, this energy flow leaves oscillations to the energy evolution, and leads to a balanced state of the two energies where both asymptote to power-law time evolution with slopes shallower than that for the turbulence kinetic energy of homogeneous isotropic turbulence. We discuss that the energy evolution can differ more significantly from that of homogeneous isotropic turbulence when there is a time variation of the gravitational potential. Morphologically, ICM turbulence can show a layered vertical structure and large horizontal vortical eddies in the central regions with the greatest density stratification. In addition, we find that the coefficient in the linear density fluctuation–turbulence Mach number relation caused by density stratification is in general a variable with position and time.

• Sponsoring Organization: USDOE
• OSTI ID: 1523665
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 487; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English