  The stellar core formation and high speed jets driven by the formed core are
studied by using three-dimensional resistive MHD nested grid simulations.
Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic
field, we calculate the cloud evolution from the molecular cloud core (n = 10^6
cm^-3, r_c = 4.6 times 10^4 AU) to the stellar core (n \simeq 10^23 cm^-3, r_c
\simeq 1 solar radius). We resolve cloud structure over 7 orders of magnitude
in spatial extent and over 17 orders of magnitude in density contrast. For
comparison, we calculate two models: resistive and ideal MHD models. Both
models have the same initial condition, but the former includes dissipation
process of magnetic field while the latter does not. The magnetic fluxes in
resistive MHD model are extracted from the first core during 10^12 cm^-3 < n <
10^16 cm^-3 by Ohmic dissipation. Magnetic flux density of the formed stellar
core (n \simeq 10^20 cm^-3) in resistive MHD model is two orders of magnitude
smaller than that in ideal MHD model. Since magnetic braking is less effective
in resistive MHD model, rapidly rotating stellar core (the second core) is
formed. After stellar core formation, the magnetic field of the core is largely
amplified both by magneto-rotational instability and the shearing motion
between the stellar core and ambient medium. As a consequence, high speed
(simeq 45 km,s^-1) jets are driven by the second core, which results in strong
mass ejection. A cocoon-like structure around the second core also forms with
clear bow shocks.
