Long Term Evolution of Magnetized Bubbles in Galaxy Clusters

We have performed nonlinear ideal magnetohydrodynamic simulations of the long term evolution of a magnetized low-density “bubble” plasma formed by a radio galaxy in a stratified cluster medium. It is found that about 3.5% of the initial magnetic energy remains in the bubble after ∼ 8 × 10 years, and the initial magnetic bubble expansion is adiabatic. The bubble can survive for at least 8 × 10 years due to the stabilizing effect of the bubble magnetic field on Rayleigh-Taylor and Kelvin-Holmholtz instabilities, possibly accounting for “ghost cavities” as observed in Perseus-A. A filament structure spanning about 500 kpc is formed along the path of bubble motion. The mean value of the magnetic field inside this structure is ∼ 0.88 μG at ∼ 8× 10 years. Finally, the initial bubble momentum and rotation have limited influence on the long term evolution of the bubble. Subject headings: galaxies: jets —magnetic fields —MHD —methods: numerical