Three‐dimensional Magnetohydrodynamic Simulations of Cold Fronts in Magnetically Turbulent ICM

Steep gradients of temperature and density, called cold fronts, are observedby Chandra in a leading edge of subclusters moving through the intraclustermedium (ICM). The presence of cold fronts indicates that thermal conductionacross the front is suppressed by magnetic fields. We carried outthree-dimensional magnetohydrodynamic (MHD) simulations including anisotropicthermal conduction of a subcluster moving through a magnetically turbulent ICM.We found that turbulent magnetic fields are stretched and amplified by shearflows along the interface between the subcluster and the ambient ICM. Sincemagnetic fields reduce the efficiency of thermal conduction across the front,the cold front survives at least 1 Gyr. We also found that a moving subclusterworks as an amplifier of magnetic fields. Numerical results indicate thatstretched turbulent magnetic fields accumulate behind the subcluster and arefurther amplified by vortex motions. The moving subcluster creates a long tailof ordered magnetic fields, in which the magnetic field strength attains plasmabeta < 10.