In a growing number of clusters radio sources are seen to displace the thermal ICM in X-ray cavities with scales ~10 kpc.
These 'radio bubbles' are sometimes obviously attached to current AGNs in the cluster core, but some
radio bubbles appear to be free `relics'. Some are radio quiet, `radio ghosts'.  These observations infer that
outflows from AGNs can inflate bubbles in the ICM, which may then survive for extended periods on their own. 

Such bubbles should be unstable to instabilities, such as the Rayleigh-Taylor and Kelvin-Helmholtz
instabilities, so their survivability is not clear. One possible way the bubbles may be stabilized is through
magnetic fields within the ICM and the bubbles. The animations below are results of a 2D MHD simulation study
designed to explore the roles of weak magnetic fields in stabilizing bubbles.

The bubbles were inflated in a statified, isothermal ICM atmosphere in hydrostatic equilibrium in a realistic
gravitational field that decreased roughly inversely with height. They were inflated from a cylindrical region
of radius 2 kpc for finite periods of time ranging upwards from 10 Myr. The undisturbed cluster magnetic field was
horizontal to the right with a constant ratio of gas to magnetic pressure, or 'beta'. The magnetic field inside the bubble was circumferential, with either a counterclockwise or a clockwise sense, and isolated from the ICM field at the start
of the simulation. Frame counter measures time in 0.5 Myr units.