YSO喷流中的速度不对称性：内在和外在机制
Velocity asymmetries in YSO jets: Intrinsic and extrinsic mechanisms
摘要：
一个公认的事实是，一些YSO喷流（例如RW Aur）在其蓝移和红移部分之间显示出不同的传播速度，这一特征可能与中央发动机或喷流传播的环境有关。为了了解不对称的YSO射流速度的起源，我们调查了两个候选机制的效率，一个是基于系统的固有特性，另一个是基于外部介质的作用。特别是，平行或反平行配置之间的原恒星磁层和磁盘磁场被认为是和由此产生的动力学检查在一个理想的和一个电阻磁流体动力学（MHD）制度。此外，我们还探索了分子云密度分布不均匀所导致的环境压力中的电势差的影响。理想和电阻轴对称的数值模拟进行了各种模型，所有这些都是基于两个解析解的组合，一个磁盘风和恒星外流。我们发现，喷流速度不对称确实可以发生时，多极磁矩存在于星盘系统，以及当被认为是不均匀的环境。后一种情况是一种外部机制，可以很容易地解释这种现象的大时间尺度，而前一种情况则自然地将其与YSO的内在性质联系起来。[删节]
英文摘要：
It is a well established fact that some YSO jets (e.g. RW Aur) display different propagation speeds between their blue and red shifted parts, a feature possibly associated with the central engine or the environment in which the jet propagates. In order to understand the origin of asymmetric YSO jet velocities, we investigate the efficiency of two candidate mechanisms, one based on the intrinsic properties of the system and one based on the role of the external medium. In particular, a parallel or anti-parallel configuration between the protostellar magnetosphere and the disk magnetic field is considered and the resulting dynamics are examined both in an ideal and a resistive magneto-hydrodynamical (MHD) regime. Moreover, we explore the effects of a potential difference in the pressure of the environment, as a consequence of the non-uniform density distribution of molecular clouds. Ideal and resistive axisymmetric numerical simulations are carried out for a variety of models, all of which are based on a combination of two analytical solutions, a disk wind and a stellar outflow. We find that jet velocity asymmetries can indeed occur both when multipolar magnetic moments are present in the star-disk system as well as when non-uniform environments are considered. The latter case is an external mechanism that can easily explain the large time scale of the phenomenon, whereas the former one naturally relates it to the YSO intrinsic properties. [abridged]
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