  Low cooling plasmas associated with large kinetic energies are likely to be
the origin of the kpc-extended and well collimated extra-galactic jets. It is
proposed that jets are launched from a layer, governed by a highly diffusive,
super-Keplerian rotating and thermally dominated by virial-hot and magnetized
ion-plasma. The launching layer is located between the accretion disk and the
corona surrounding the nucleus. The matter in the layer is causally connected
to both the disk and to the central engine. Moreover we find that coronae, in
the absence of heating from below, are dynamically unstable to thermal
ion-conduction, and that accretion disks become intrinsically
advection-dominated. We confirm the capability of this multi-layer model to
form jets by carrying out 3D axisymmetric quasi-stationary MHD calculations
with high spatial resolution, and taking into account turbulent and magnetic
diffusion. The new multi-layer topology accommodates several previously
proposed elements for jet-initiation, in particular the ion-torus, the
magneto-centrifugal and the truncated disk - advective tori models.
