Turbulence, magnetic fields, and plasma physics in clusters of galaxies

By A. Schekochihin, S. Cowley. 2006

160 citations recorded by the source corpus.

Observations of galaxy clusters show that the intracluster medium (ICM) is likely to be turbulent and is certainly magnetized. The properties of this magnetized turbulence are determined both by fundamental nonlinear magnetohydrodynamic interactions and by the plasma physics of the ICM, which has very low collisionality. Cluster plasma threaded by weak magnetic fields is subject to firehose and mirror instabilities. These saturate and produce fluctuations at the ion gyroscale, which can scatter particles, increasing the effective collision rate and, therefore, the effective Reynolds number of the ICM. A simple way to model this effect is proposed. The model yields a self-accelerating fluctuation dynamo whereby the field grows explosively fast, reaching the observed, dynamically important, field strength in a fraction of the cluster lifetime independent of the exact strength of the seed field. It is suggested that the saturated state of the cluster turbulence is a combination of the conventional isotropic magnetohydrodynamic turbulence, characterized by folded, direction-reversing magnetic fields and an Alfven-wave cascade at collisionless scales. An argument is proposed to constrain the reversal scale of the folded field. The picture that emerges appears to be in qualitative agreement with observations of magnetic fields in clusters.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f9da133ca7f7bb2be52d9ad0ae5e9af221b3b8ed

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In Astronomy and Astrophysics

Citations in the corpus

Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission (2007, background): “Furthermore, shearing motions induced by oblique shocks stretch these field lines which leads to a larger magnetic coherence length of two-dimensional field configurations (Schekochihin & Cowley 2006).”
ASTROPHYSICAL GYROKINETICS: KINETIC AND FLUID TURBULENT CASCADES IN MAGNETIZED WEAKLY COLLISIONAL PLASMAS (2007, background): “It is not currently known what determines the reversal scale.45 Observations, while tentatively confirming the existence of very 45 See Schekochihin & Cowley (2006) for a detailed presentation of our views on the interplay between turbulence, magnetic field anplasma effects in cluster; for further…”
Astrophysical Gyrokinetics: Basic Equations and Linear Theory (2005, methodology): “For a detailed discussion of these results, we refer the reader to Goldreich and Sridhar’s original papers or to a review by Schekochihin & Cowley (2006a).”
Cosmic ray transport in galaxy clusters: implications for radio halos, gamma-ray signatures, and cool core heating (2010, background): “…et al. (1999b); Inogamov & Sunyaev (2003); Schuecker et al. (2004); Faltenbacher et al. (2005); Dolag et al. (2005); Subramanian et al. (2006); Schekochihin & Cowley (2006); Vazza et al. (2006); Iapichino et al. (2008); Iapichino & Niemeyer (2008); Maier et al. (2009); Battaglia et al.…”
Compressible turbulence in galaxy clusters: physics and stochastic particle re-acceleration (2007, background): “These instabilities in the ICM may induce scatterings of thermal ions which reduce the effective mean free path and further increase the value of the Reynolds number (e.g., Schekochihin & Cowley 2006; Lazarian & Beresnyak 2006).”