The HBI in a quasi-global model of the intracluster medium

Abstract

In this paper we investigate how convective instabilities influence heat conduction in the intracluster medium (ICM) of cool-core galaxy clusters. The ICM is a high-beta, weakly collisional plasma in which the transport of momentum and heat is aligned with the magnetic field. The anisotropy of heat conduction, in particular, gives rise to instabilities that can access energy stored in a temperature gradient of either sign. We focus on the heat-flux buoyancy-driven instability (HBI), which feeds on the outwardly increasing temperature profile of cluster cool cores. Our aim is to elucidate how the global structure of a cluster impacts on the growth and morphology of the linear HBI modes when in the presence of Braginskii viscosity, and ultimately on the ability of the HBI to thermally insulate cores. We employ an idealised quasi-global model, the plane-parallel atmosphere, which captures the essential physics -- e.g. the global radial profile of the cluster -- while letting the problem remain analytically tractable. Our main result is that the dominant HBI modes are localised to the the innermost (~<20%) regions of cool cores. It is then probable that, in the nonlinear regime, appreciable field-line insulation will be similarly localised. Thus, while radio-mode feedback appears necessary in the central few tens of kpc, heat conduction may be capable of offsetting radiative losses throughout most of a cool core over a significant fraction of the Hubble time. Finally, our linear solutions provide a convenient numerical test for the nonlinear codes that tackle the saturation of such convective instabilities in the presence of anisotropic transport.

MNRAS, in press; minor modifications from v1

References in corpus (8)

• Athena: A New Code for Astrophysical MHD
• Intracluster Medium Entropy Profiles for a Chandra Archival Sample of Galaxy Clusters
• Buoyancy Instabilities in Weakly Magnetized Low Collisionality Plasmas
• Anisotropic Thermal Conduction and the Cooling Flow Problem in Galaxy Clusters
• Nonlinear Simulations of the Heat Flux Driven Buoyancy Instability and its Implications for Galaxy Clusters
• Simulations of MHD Instabilities in Intracluster Medium Including Anisotropic Thermal Conduction
• The Effects of Anisotropic Viscosity on Turbulence and Heat Transport in the Intracluster Medium
• Regulation of thermal conductivity in hot galaxy clusters by MHD turbulence

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• Plasma Instabilities in the Context of Current Helium Sedimentation Models: Dynamical Implications for the ICM in Galaxy Clusters
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• Stability Analysis of Convection in the Intracluster Medium
• On the Helium fingers in the intracluster medium
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