标题： 分层周围介质中三维模拟的原恒星喷流可能机制 显示英文标题

标题： A Possible Mechanism for Wiggling Protostellar Jets from 3D Simulations in a Stratified Ambient Medium

摘要： 大多数聚束状的超音速原恒星喷流显示出聚束振荡和结状结构（例如，Haro 6-5B喷流），并且经常在该结构与终端弓激波之间揭示出一个长长的间隙。在少数情况下，没有这种终端特征的证据。我们提出了三维光滑粒子流体动力学模拟，这表明这种形态可能是传播冷却喷流与非均匀周围介质相互作用的结果。在周围气体密度（和压力）梯度增加的区域，我们发现它倾向于压缩围绕光束的冷低压冲击物质低密度包层，破坏头部类似弓激波的结构，并增强光束聚焦、摆动以及内部行进激波。在周围密度（和压力）降低的区域，流体变宽并放松，变得非常微弱。这可以解释像Haro 6-5B喷流这样的系统中的“不可见”段。在这种情况下，弓激波可能是一个较早流出阶段的遗迹，正如先前所建议的那样，或者是喷流在撞击周围介质的更密部分后重新出现的地方。 显示英文摘要

摘要： Most collimated supersonic protostellar jets show a collimated wiggling, and knotty structure (e.g., the Haro 6-5B jet) and frequently reveal a long gap between this structure and the terminal bow shock. In a few cases, there is no evidence of such a terminal feature. We present three-dimensional smoothed particle hydrodynamical simulations which suggest that this morphology may be due to the interaction of the propagating cooling jet with a non-homogeneous ambient medium. In regions where the ambient gas has an increasing density (and pressure) gradient, we find that it tends to compress the cold, low-pressure cocoon of shocked material that surrounds the beam, destroy the bow shock-like structure at the head, and enhance beam focusing, wiggling, and internal traveling shocks. In ambient regions of decreasing density (and pressure), the flow widens and relaxes, becoming very faint. This could explain ``invisible'' segments in systems like the Haro 6-5B jet. The bow shock in these cases could be a relic of an earlier outflow episode, as previously suggested, or the place where the jet reappears after striking a denser portion of the ambient medium.