TY - JOUR

T1 - Suppressed heat conductivity in the intracluster medium

T2 - implications for the magneto-thermal instability

AU - Berlok, Thomas

AU - Quataert, Eliot

AU - Pessah, Martin E.

AU - Pfrommer, Christoph

PY - 2021/7/1

Y1 - 2021/7/1

N2 - In the outskirts of the intracluster medium (ICM) in galaxy clusters, the temperature decreases with radius. Due to the weakly collisional nature of the plasma, these regions are susceptible to the magneto-thermal instability (MTI), which can sustain turbulence and provide turbulent pressure support in the ICM. This instability arises due to heat conduction directed along the magnetic field, with a heat conductivity which is normally assumed to be given by the Spitzer value. Recent numerical studies of the ion mirror and the electron whistler instability using particle-in-cell codes have shown that microscale instabilities can lead to a reduced value for the heat conductivity in the ICM. This could in turn influence the efficiency with which the MTI drives turbulence. In this paper, we investigate the influence of reduced heat transport on the non-linear evolution of the MTI. We study plane-parallel, initially static atmospheres and employ a subgrid model that mimics the influence of the mirror instability on the heat conductivity. We use this subgrid model to assess the effect of microscales on the large-scale dynamics of the ICM. We find that the non-linear saturation of the MTI is surprisingly robust in our simulations. Over a factor of similar to 10(3) in the thermal-to-magnetic pressure ratio and collisionality, we find at most modest changes to the saturation of the MTI with respect to reference simulations where heat transport is unsuppressed.

AB - In the outskirts of the intracluster medium (ICM) in galaxy clusters, the temperature decreases with radius. Due to the weakly collisional nature of the plasma, these regions are susceptible to the magneto-thermal instability (MTI), which can sustain turbulence and provide turbulent pressure support in the ICM. This instability arises due to heat conduction directed along the magnetic field, with a heat conductivity which is normally assumed to be given by the Spitzer value. Recent numerical studies of the ion mirror and the electron whistler instability using particle-in-cell codes have shown that microscale instabilities can lead to a reduced value for the heat conductivity in the ICM. This could in turn influence the efficiency with which the MTI drives turbulence. In this paper, we investigate the influence of reduced heat transport on the non-linear evolution of the MTI. We study plane-parallel, initially static atmospheres and employ a subgrid model that mimics the influence of the mirror instability on the heat conductivity. We use this subgrid model to assess the effect of microscales on the large-scale dynamics of the ICM. We find that the non-linear saturation of the MTI is surprisingly robust in our simulations. Over a factor of similar to 10(3) in the thermal-to-magnetic pressure ratio and collisionality, we find at most modest changes to the saturation of the MTI with respect to reference simulations where heat transport is unsuppressed.

KW - conduction

KW - diffusion

KW - instabilities

KW - magnetic fields

KW - plasmas

KW - galaxies: clusters: intracluster medium

KW - SOUND-PROOF TREATMENTS

KW - BUOYANCY INSTABILITIES

KW - PLASMA INSTABILITIES

KW - ENERGY-CONSERVATION

KW - GALAXY CLUSTERS

KW - GRAVITY-WAVES

KW - SIMULATIONS

KW - STABILITY

KW - EVOLUTION

KW - FIREHOSE

U2 - 10.1093/mnras/stab832

DO - 10.1093/mnras/stab832

M3 - Journal article

VL - 504

SP - 3435

EP - 3454

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 3

ER -