The Magnetothermal Instability in the Intracluster Medium

The electron mean free path in the intracluster medium (ICM) of galaxy clusters is much larger than the gyroradius; thus, heat is transported anisotropically along magnetic field lines. We show that the intracluster medium is unstable to the magnetothermal instability (MTI) using MHD simulations with anisotropic thermal conduction. As a result of the MTI, we find that the temperature profile of the ICM can be substantially modified on timescales of several billion years while the magnetic field is amplified by dynamo action to more than fifty times the original energy. We also show that the instability drives field lines to become preferentially radial leading to conduction that is a highly efficient fraction of the Spitzer conductivity. As such, we present the first self-consistent calculation of the effective thermal conductivity in the ICM. Subject headings: convection—galaxies: clusters: general—instabilities—MHD—plasmas—X-rays: galaxies: clusters