  Radio sources of low power are the most common in the universe. Their jets
typically move at nonrelativistic velocity and show plume-like morphologies
that in many instances appear distorted and bent. We investigate the role of
magnetic field on the propagation and evolution of low-power jets and the
connection between the field intensity and the resulting morphology. The
problem is addressed by means of three-dimensional magnetohydrodynamic (MHD)
simulations. We consider supersonic jets that propagate in a stratified medium.
The ambient temperature increases with distance from the jet origin maintaining
constant pressure. Jets with low magnetization show an enhanced collimation at
small distances with respect to hydrodynamic (HD) cases studied in a previous
paper. These jets eventually evolve in a way similar to the HD cases. Jets with
higher magnetization are affected by strong nonaxisymmetric modes that lead to
the sudden jet energy release. From there on, distorted plumes of jet material
move at subsonic velocities. This transition is associated with the formation
of structures reminiscent of the `warm spots' observed in wide-angle-tail (WAT)
sources.
