Magneto-Thermal Instability In Galaxy Clusters I: Theory and Two-Dimensional Simulations
arXiv:2110.13918 · doi:10.1093/mnras/stac974
Abstract
Determining the origin of turbulence in galaxy clusters, and quantifying its transport of heat, is an outstanding problem, with implications for our understanding of their thermodynamic history and structure. As the dilute plasma of the intracluster medium (ICM) is magnetized, heat and momentum travel preferentially along magnetic field lines. This anisotropy triggers a class of buoyancy instabilities that destabilize the ICM, and whose turbulent motions can augment or impede heat transport. We focus on the magneto-thermal instability (MTI), which may be active in the periphery of galaxy clusters. We aim to take a fresh look at the problem and construct a general theory that explains the MTI saturation mechanism and provides scalings and estimates for the turbulent kinetic energy, magnetic energy, and heat flux. We simulate MTI turbulence with a Boussinesq code, SNOOPY, which, in contrast to previous work, allows us to perform an extensive sampling of the parameter space. In two dimensions the saturation mechanism involves an inverse cascade carrying kinetic energy from the short MTI injection scales to larger scales, where it is arrested by the stable entropy stratification; at a characteristic "buoyancy scale", the energy is dumped into large-scale g-modes, which subsequently dissipate. Consequently, the entropy stratification sets an upper limit on the size and strength of turbulent eddies. Meanwhile, the MTI conveys a substantial fraction of heat, despite the tangled geometry of the magnetic field. In a companion paper, these results are extended to three-dimensional flows, and compared to real cluster observations.
20 pages, 19 figures, submitted to MNRAS
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Cited by in corpus (7)
- Investigating the turbulent hot gas in X-COP galaxy clusters
- Magneto-Thermal Instability In Galaxy Clusters II: Three-Dimensional Simulations
- Thermal conductivity with bells and whistlers: suppression of the magnetothermal instability in galaxy clusters
- Does the magneto-thermal instability survive whistler-suppression of thermal conductivity in galaxy clusters?
- Dynamical properties and detectability of the magneto-thermal instability in the intracluster medium
- Non-linear saturation and energy transport in global simulations of magneto-thermal turbulence in the stratified intracluster medium
- Simulating cosmic ray electron spectra and radio emission from an AGN jet outburst in a cool-core cluster