  Transverse stratification is a common intrinsic feature of astrophysical
jets. There is growing evidence that jets in radio galaxies consist of a fast
low density outflow at the jet axis, surrounded by a slower, denser, extended
jet. The inner and outer jet components then have a different origin and
launching mechanism, making their effective inertia, magnetization, associated
energy flux and angular momentum content different as well. Their interface
will develop differential rotation, where disruptions may occur. We here
investigate the stability of rotating, two-component relativistic outflows
typical for jets in radio galaxies. For this purpose, we parametrically explore
the long term evolution of a transverse cross-section of radially stratified
jets numerically With grid-adaptive relativistic MHD simulations, augmented
with approximate linear stability analysis. We study the influence of
dynamically important poloidal magnetic fields, with varying contributions of
the inner component jet to the total kinetic energy flux of the jet, on their
non-linear azimuthal stability. We demonstrate that two-component jets with
high kinetic energy flux, and an inner jet effective inertia which is higher
than the outer jet effective inertia are subject to the development of a
relativistically enhanced, rotation-induced Rayleigh-Taylor type instability.
This instability plays a major role in decelerating the inner jet and the
overall jet decollimation. This novel deceleration scenario can partly explain
the radio source dichotomy, relating it directly to the efficiency of the
central engine in launching the inner jet component. The FRII/FRI transition
could then occur when the relative kinetic energy flux of the inner to the
outer jet grows beyond a certain treshold.
