The reduction of thermal conductivity by magnetic fields in clusters of galaxies

Abstract

Tangled magnetic fields reduce heat fluxes in the intracluster medium by forcing heat to flow along the field lines rather than by more direct routes. The presence of field lines of different temperatures mixed together leads to an inhomogeneous multiphase description of the intracluster medium. A description of the magnetic field as a random walk leads to expressions for the mean temperature, temperature dispersion and heat flux. If regions exist in the cluster which are isolated from the rest of the intracluster medium then these are natural sites for thermal instability leading to optical filamentation.