Decaying turbulence and magnetic fields in galaxy clusters

We explore the decay of turbulence and magnetic fields generated by fluctuation dynamo action in the context of galaxy clusters where such a decaying phase can occur in the aftermath of a major merger event. Using idealized numerical simulations that start from a kinetically dominated regime we focus on the decay of the steady state rms velocity and the magnetic field for a wide range of conditions that include varying the compressibility of the flow, the forcing wavenumber, and the magnetic Prandtl number, Irrespective of the compressibility of the flow, both the rins velocity and the rins magnetic field decay as a power law in time, In the subsonic case we find that the exponent of the power law is consistent with the -3/5 scaling reported in previous studies, However, in the transonic regime both the rms velocity and the magnetic acid initially undergo rapid decay with an approximate to t(-1.1) scaling with time. This is followed by a phase of slow decay where the decay of the rms velocity exhibits an approximate to-3/5 scaling in time, while the rms magnetic acid scales as approximate to-5/7. Furthermore, analysis of the Faraday rotation measure (RM) reveals that the Faraday RM also decays as a power law in time approximate to t(-5/7); steeper than the similar to t(-2/5) scaling obtained in previous simulations of magnetic acid decay in subsonic turbulence. Apart from galaxy clusters, our work can have potential implications in the study of magnetic fields in elliptical galaxies.