Suppression of AGN-Driven Turbulence by Magnetic Fields in a
  Magnetohydrodynamic Model of the Intracluster Medium
  We investigate the role of AGN feedback in turbulent heating of galaxy
clusters. Specifically, we analyze the production of turbulence by g-modes
generated by the supersonic expansion and buoyant rise of AGN-driven bubbles.
Previous work which neglects magnetic fields has shown that this process is
inefficient, with less than 1% of the injected energy ending up in turbulence.
This inefficiency is primarily due to the fact that the bubbles are shredded
apart by hydrodynamic instabilities before they can excite sufficiently strong
g-modes. Using a plane-parallel model of the ICM and 3D ideal MHD simulations,
we examine the role of a large-scale magnetic field which is able to drape
around these rising bubbles, preserving them from hydrodynamic instabilities.
We find that, while magnetic draping appears better able to preserve AGN-driven
bubbles, the driving of g-modes and the resulting production of turbulence is
still inefficient. The magnetic tension force prevents g-modes from
transitioning into the nonlinear regime, suppressing turbulence in our model
ICM. Our work highlights the ways in which ideal MHD is an insufficient
description for the cluster feedback process, and we discuss future work such
as the inclusion of anisotropic viscosity as a means of simulating high $\beta$
plasma kinetic effects. These results suggest the hypothesis that other
mechanisms of heating the ICM plasma such as sound waves or cosmic rays may be
responsible for observed feedback in galaxy clusters.
