  The propagation of active galactic nucleus jets depends both on the
environment into which they propagate and on their internal structure. To test
the impact that different magnetic topologies have on the observable properties
of radio galaxies on kpc scales, we conducted a series of magneto-hydrodynamic
simulations of jets injected with different magnetic field configurations
propagating into a gaseous atmosphere modeled on the Perseus cluster. The
simulations show that the structure of the field affects the collimation and
propagation of the jets on cluster scales and thus the morphology of the radio
lobes inflated by the jets, due both to magnetic collimation and the
development of dynamical instabilities in jets with different magnetic
topologies. In all cases, the simulations show a distinct reversal of the
sychrotron spectral age gradient in the radio lobes about a dynamical time
after the jets turn off due to large scale circulation inside the radio lobe,
driven primarily by buoyancy, which could provide a way to constrain the age of
radio sources in cluster environments without the need for detailed spectral
modeling and thus constrain the radio mode feedback efficiency. We suggest a
robust diagnostic to search for such age gradients in multi-frequency radio
data.
