Yu-hsuan Liu (National Taiwan Normal University)Yueh-Ning Lee (National Taiwan Normal University)
It is widely accepted that stars form within dense regions of moleculars clouds, under the influence of self-gravity. Due to the conservation of anguler momenentum, the collapse move with the Keplerian rotation (0.1pc~100AU). However, most Prestellar cores are magnetized. If an ideal magnetohydrodynamic (MHD) model is used to describe this collapse, a magnetic field will prevent the formation of disk due to angular momentum transport. However, if non-ideal MHD processes, that is, ambipolar diffusion, Ohmic effect, and hall effect, are taken into account, the magnetic braking will be reduced. We hope to explore the Hall effect model and try to derive the theoretical disc size. We further discuss the bimodel disc size caused by the angular momentum being parallel and anti-parallel to the magnetic field.