  The two types of Fanaroff-Riley radio loud galaxies, FRI and FRII, exhibit
strong jets but with different properties. These differences may be associated
to the central engine and/or the external medium. Aims: The AGN classification
FRI and FRII can be linked to the rate of electromagnetic Poynting flux
extraction from the inner corona of the central engine by the jet. The
collimation results from the distribution of the total electromagnetic energy
across the jet, as compared to the corresponding distribution of the thermal
and gravitational energies. We use exact solutions of the fully relativistic
magnetohydrodynamical (GRMHD) equations obtained by a nonlinear separation of
the variables to study outflows from a Schwarzschild black hole corona. A
strong correlation is found between the jet features and the energetic
distribution of the plasma of the inner corona which may be related to the
efficiency of the magnetic rotator. It is shown that observations of FRI and
FRII jets may be partially constrained by our model for spine jets. The
deceleration observed in FRI jets may be associated with a low magnetic
efficiency of the central magnetic rotator and an important thermal confinement
by the hot surrounding medium. Conversely, the strongly collimated and
accelerated FRII outflows may be self collimated by their own magnetic field
because of the high efficiency of the central magnetic rotator.
