Second Core Formation and High Speed Jets: Resistive MHD Nested Grid Simulations

The stellar core formation and high speed jets driven by the formed core are studied by using three-dimensional resistive magnetohydrodynamical (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 (nc = 10 6 cm, rc = 4.6×10 4 AU) to the stellar core (nc ≃ 10 23 cm, rc ≃ 1R⊙), where nc and rc denote the central density and radius of the objects, respectively. 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 cm < nc < 10 16 cm by Ohmic dissipation. Magnetic flux density of the formed stellar core (nc ≃ 10 20 cm) 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 [email protected] [email protected] [email protected]