  We present three-dimensional magnetohydrodynamic (MHD) simulations of
superbubbles, to study the importance of MHD effects in the interpretation of
images from recent surveys of the Galactic plane. These simulations focus
mainly on atmospheres defined by an exponential density distribution and the
Dickey & Lockman (1990) density distribution. In each case, the magnetic field
is parallel to the Galactic plane and we investigate cases with either infinite
scale height (constant magnetic field) or a constant ratio of gas pressure to
magnetic pressure. The three-dimensional structure of superbubbles in these
simulations is discussed with emphasis on the axial ratio of the cavity as a
function of magnetic field strength and the age of the bubble. We investigate
systematic errors in the age of the bubble and scale height of the surrounding
medium that may be introduced by modeling the data with purely hydrodynamic
models. Age estimates derived with symmetric hydrodynamic models fitted to an
asymmetric magnetized superbubble can differ by up to a factor of four,
depending on the direction of the line of sight. The scale height of the
surrounding medium based on the Kompaneets model may be up to 50% lower than
the actual scale height. We also present the first ever predictions of Faraday
rotation by a magnetized superbubble based on three-dimensional MHD
simulations. We emphasize the importance of MHD effects in the interpretation
of observations of superbubbles.
