Formation of Unipolar Outflow and Protostellar Rocket Effect in Magnetized Turbulent Molecular Cloud Cores

Abstract

Observed protostellar outflows exhibit a variety of asymmetrical features, including remarkable unipolar outflows and bending outflows. Revealing the formation and early evolution of such asymmetrical protostellar outflows, especially the unipolar outflows, is essential for a better understanding of the star and planet formation because they can dramatically change the mass accretion and angular momentum transport to the protostars and protoplanetary disks. Here we perform three-dimensional nonideal magnetohydrodynamics simulations to investigate the formation and early evolution of the asymmetrical protostellar outflows in magnetized turbulent isolated molecular cloud cores. We find, for the first time to our knowledge, that the unipolar outflow forms even in the single low-mass protostellar system. The results show that the unipolar outflow is driven in the weakly magnetized cloud cores with the dimensionless mass-to-flux ratios of μ = 8 and 16. Furthermore, we find the protostellar rocket effect of the unipolar outflow, which is similar to the launch and propulsion of a rocket. The unipolar outflow ejects the protostellar system from the central dense region to the outer region of the parent cloud core, and the ram pressure caused by its ejection suppresses the driving of additional new outflows. In contrast, the bending bipolar outflow is driven in the moderately magnetized cloud core with μ = 4. The ratio of the magnetic to turbulent energies of a parent cloud core may play a key role in the formation of asymmetrical protostellar outflows.

Multiple Misaligned Outflows and Warped Accretion Flows in the Proto-multiple System Per-emb-8 and 55

“…Monopolar outflows have been observed in a few protostellar sources, although they are not often seen (Wu et al 2004;Stephens et al 2017). As shown in the theoretical calculation, monopolar outflows can form depending on the magnetic field structures of star+disk systems and the energy ratio of the magnetic field to turbulence in protostellar envelopes (Lovelace et al 2010;Takaishi et al 2024). It is also possible that Per-emb-55 A and B both actually launch bipolar outflows, but one of the lobes is obscured by extended ambient clouds if its line-of-sight velocity is coincident with the cloud velocity.…”