  In order to better understand the origin and evolution of relic radio bubbles
in clusters of galaxies, we report on an extensive set of 2D MHD simulations of
hot buoyant bubbles evolving in a realistic intracluster medium. Our bubbles
are inflated near the base of the ICM over a finite time interval from a region
whose magnetic field is isolated from the ICM. We confirm both the early
conjecture from linear analysis and the later results based on preformed MHD
bubbles; namely, that very modest ICM magnetic fields can stabilize the rising
bubbles against disruption by Rayleigh-Taylor and Kelvin-Helmholtz
instabilities. We find in addition that amplification of the ambient fields as
they stretch around the bubbles can be sufficient to protect the bubbles or
their initial fragments even if the fields are initially much too weak to play
a significant role early in the evolution of the bubbles. Indeed, even with
initial fields less than a micro-Gauss and values of $\beta = P_g/P_b$
approaching $10^5$, magnetic stresses in our simulations eventually became
large enough to influence the bubble evolution. Magnetic field influence also
depends significantly on the geometry of the ICM field and on the topology of
the field at the bubble/ICM interface. For example, reconnection of
anti-parallel fields across the bubble top greatly reduced the ability of the
magnetic field to inhibit disruptive instabilities. Our results confirm earlier
estimates of $10^8$ yr for relic radio bubble lifetimes and show that magnetic
fields can account for the long term stability of these objects against
disruption by surface instabilities. In addition these calculations show that
lifting and mixing of the ambient ICM may be a critical function of field
geometries in both the ICM and in the bubble interior.
