Analysis of the Properties of Primary Protostellar Disks Depending on the Initial Magnetic Field of Parent Protostellar Clouds

We analyze the magnetohydrodynamic (MHD) simulations of the isothermal collapse of protostellar clouds with masses of 1 and 10 1pt {M } and various initial dimensionless ratios of magnetic to gravitational energy, { ₌}. Based on the simulations, we study how the mass, size, and angular momentum of primary protostellar disks—magnetostatic structures formed in the early collapse stages and flattened along the cloud’s magnetic field lines—change during the evolution. The analysis shows that the radii of the primary disks increase linearly with { ₌} from 400 to 7000 AU for a moderate magnetic field, corresponding to the mean observed values { ₌} = 0. 1- 0. 2. In this case, the masses of the primary disks range from 0. 1 to 0. 5 of the cloud’s mass, and their angular momenta lie in the range from 0. 05 to 0. 2 of the cloud’s initial angular momentum. The growth of the primary disk’s mass and angular momentum with { ₌} indicates that these quantities are determined primarily by the mass inflow from the envelope. The mass inflow rate is of {10^{ - 4}} 1pt {M } /year. The magnetic braking of the primary disk dominates over the angular momentum inflow from the envelope in the clouds with a strong magnetic field only, { ₌} > 0. 4. In this case, a cloud as a whole evolves into a state of magnetostatic equilibrium, and its angular momentum decreases with increasing { ₌}. Our results indicate that the observed scatter in the magnetic field strengths of protostellar clouds should manifest itself in a diversity of the properties of primary protostellar disks and, consequently, result in different star formation scenarios.