  We show three-dimensional magnetohydrodynamical simulations of core collapse
supernova in which the progenitor has magnetic fields inclined to the rotation
axis. The simulations employed a simple empirical equation of state in which
the pressure of degenerate gas is approximated by piecewise polytropes for
simplicity. Neither energy loss due to neutrino is taken into account for
simplicity. The simulations start from the stage of dynamical collapse of an
iron core. The dynamical collapse halts at $ t $ = 189 ms by the pressure of
high density gas and a proto-neutron star (PNS) forms. The evolution of PNS was
followed about 40 milli-seconds in typical models. When the initial rotation is
mildly fast and the initial magnetic fields are mildly strong, bipolar jets are
launched from an upper atmosphere ($ r \sim 60 {\rm km} $) of the PNS. The jets
are accelerated to $ \sim 3 \times 10 ^4 $ km s$^{-1}$, which is comparable to
the escape velocity at the foot point. The jets are parallel to the initial
rotation axis. Before the launch of the jets, magnetic fields are twisted by
rotation of the PNS. The twisted magnetic fields form torus-shape multi-layers
in which the azimuthal component changes alternately. The formation of magnetic
multi-layers is due to the initial condition in which the magnetic fields are
inclined with respect to the rotation axis. The energy of the jet depends only
weakly on the initial magnetic field assumed. When the initial magnetic fields
are weaker, the time lag is longer between the PNS formation and jet ejection.
It is also shown that the time lag is related to the Alfv\'en transit time.
Although the nearly spherical prompt shock propagates outward in our
simulations, it is ...
