  Recent observations by Chandra and XMM-Newton indicate there are complex
structures at the cores of galaxy clusters, such as cavities and filaments. One
plausible model for the formation of such structures is the interaction of
radio jets with the intracluster medium (ICM). To investigate this idea, we use
three-dimensional magnetohydrodynamic simulations including anisotropic
(Braginskii) viscosity to study the effect of magnetic fields on the evolution
and morphology of buoyant bubbles in the ICM. We investigate a range of
different initial magnetic field geometries and strengths, and study the
resulting x-ray surface brightness distribution for comparison to observed
clusters. Magnetic tension forces and viscous transport along field lines tend
to suppress instabilities parallel, but not perpendicular, to field lines.
Thus, the evolution of the bubble depends strongly on the initial field
geometry. We find toroidal field loops initially confined to the interior of
the bubble are best able reproduce the observed cavity structures.
