  We have performed self-consistent 2.5-dimensional nonsteady MHD numerical
simulations of jet formation as long as possible, including the dynamics of
accretion disks. Although the previous nonsteady MHD simulations for
astrophysical jets revealed that the characteristics of nonsteady jets are
similar to those of steady jets, the calculation time of these simulations is
very short compared with the time scale of observed jets. Thus we have
investigated long term evolutions of mass accretion rate, mass outflow rate,
jet velocity, and various energy flux. We found that the ejection of jet is
quasi-periodic. The period of the ejection is related to the time needed for
the initial magnetic filed to be twisted to generate toroidal filed. We compare
our results with both the steady state theory and previous 2.5-dimensional
nonsteady MHD simulations.
