Matter Infall in Collapsing Molecular Cloud Cores with an Axial Magnetic   Field
  The magnetic fields affect collapse of molecular cloud cores. Here, we consider a collapsing core with an axial magnetic field and investigate its effect on infall of matter and formation of accretion disk. For this purpose, the equations of motion of ions and neutral infalling particles are numerically solved to obtain the streamlines of trajectories. The results show that in non-steady state of ionization and ion-neutral coupling, which is not unexpected in the case of infall, the radius of accretion disk will be larger as a consequence of axial magnetic field. 
Mohsen Nejad-Asghar
astro-ph.GA