AMBIPOLAR DIFFUSION IN ACTION: TRANSIENT C SHOCK STRUCTURE AND PRESTELLAR CORE FORMATION
AMBIPOLAR DIFFUSION IN ACTION: TRANSIENT C SHOCK STRUCTURE AND PRESTELLAR CORE FORMATION
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双极扩散的实际应用：瞬态 C 震结构和星前核形成
DOI：
10.1088/0004-637x/744/2/124
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
E. Ostriker
中科院分区：
文献类型：
--
作者：
Che;E. Ostriker
我们分析了在巨大分子云中普遍存在的条件下稳定和随时间变化的C激波的性质。对于稳定的C激波，我们证明了电离平衡是成立的，并使用数值积分得到了由双极性扩散调解的激波厚度的拟合公式：Lshock∝n0−3/4v01/ 2b01 /2χ 0−1。我们的公式也符合基于离子中性动量交换的分析估计。使用与时间相关的数值模拟，我们表明，当中性点被压缩得比磁场强得多时，C冲击有一个瞬态阶段。瞬态阶段的持续时间由中性离子碰撞时间设定，tAD ~ Lshock/vdrift ~ 0.1 - 1myr。这种瞬态产生了质量与磁通比的强烈增强。在有利条件下，由于C激波瞬态阶段的磁通量损失，超临界星前核可能迅速形成和坍缩。
We analyze the properties of steady and time-dependent C shocks under conditions prevailing in giant molecular clouds. For steady C shocks, we show that ionization equilibrium holds and uses numerical integration to obtain a fitting formula for the shock thickness mediated by ambipolar diffusion, Lshock∝n0−3/4v01/2B01/2χi0−1. Our formula also agrees with an analytic estimate based on ion–neutral momentum exchange. Using time-dependent numerical simulations, we show that C shocks have a transient stage when the neutrals are compressed much more strongly than the magnetic field. The transient stage has a duration set by the neutral–ion collision time, tAD ∼ Lshock/vdrift ∼ 0.1–1 Myr. This transient creates a strong enhancement in the mass-to-magnetic flux ratio. Under favorable conditions, supercritical prestellar cores may form and collapse promptly as a result of magnetic flux loss during the transient stage of C shocks.
影响因子：
6.5
作者：
Ashmore I
通讯作者：
Ashmore I