Interaction of Fanaroff-Riley class II radio jets with a randomly
  magnetised intra-cluster medium
  A combination of three-dimensional (3D) magnetohydrodynamics (MHD) and
synthetic numerical simulations are presented to follow the evolution of a
randomly magnetised plasma that models the intra-cluster medium (ICM), under
the isolated effects of powerful, light, hypersonic and bipolar Fanaroff-Riley
class II (FR II) jets. We prescribe the cluster magnetic field (CMF) as a
Gaussian random field with a Kolmogorov-like energy spectrum. Both the power of
the jets and the viewing angle that is used for the synthetic Rotation Measure
(RM) observations are investigated. We find the model radio sources introduce
and amplify fluctuations on the RM statistical properties which we analyse as a
function of time as well as the viewing angle. The average RM and the RM
standard deviation are increased by the action of the jets. Energetics, RM
statistics and magnetic power spectral analysis consistently show that the
effects also correlate with the jets' power, and that the lightest, fastest
jets produce the strongest changes in their environment. We see jets distort
and amplify the CMFs especially near the edges of the lobes and the jets'
heads. This process leads to a flattening of the RM structure functions at
scales comparable to the source size. The edge features we find are similar to
ones observed in Hydra A. The results show that jet-produced RM enhancements
are more apparent in quasars than in radio galaxies. Globally, jets tend to
enhance the RM standard deviation which may lead to overestimations of the
CMFs' strength by about 70%. This study means to serve as a pathfinder for the
SKA, EVLA and LOFAR to follow the evolution of cosmic magnetic fields.
