用排列的晶粒追踪磁场
Tracing Magnetic Fields with Aligned Grains
摘要：
磁场在各种天体物理过程中起着至关重要的作用，包括恒星形成，物质吸积，运输过程（例如，热传输）和宇宙射线。确定磁场方向的最简单方法之一是通过由排列的尘埃颗粒的消光或/和发射产生的辐射的偏振。用磁场解释极化图的可靠性取决于我们对晶粒排列理论的理解程度。目前，颗粒排列理论是一种预测理论，其结果与观测结果很好地吻合。在它的预测中，有一个微妙的辐射力矩现象。在被发现后被遗忘了很多年之后，现在被认为是最强大的对齐方式。在这篇文章中，我将回顾晶粒排列的基本物理过程，以及目前已知的排列机制。我还将讨论不同对齐机制的可能利基。我将详细说明颗粒螺旋度概念对于理解颗粒排列的许多性质的重要性，并将证明，当颗粒与气流和辐射通量相互作用时，形状相当任意的颗粒会表现出螺旋度。
英文摘要：
Magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g., transport of heat), and cosmic rays. One of the easiest ways to determine the magnetic field direction is via polarization of radiation resulting from extinction on or/and emission by aligned dust grains. Reliability of interpretation of the polarization maps in terms of magnetic fields depends on how well we understand the grain-alignment theory. Currently the grain-alignment theory is a predictive one, and its results nicely match observations. Among its predictions is a subtle phenomenon of radiative torques. after having stayed in oblivion for many years after its discovery, is currently viewed as the most powerful means of alignment. In this article, I shall review the basic physical processes involved in grain alignment, and the currently known mechanisms of alignment. I shall also discuss possible niches for different alignment mechanisms. I shall dwell on the importance of the concept of grain helicity for understanding of many properties of grain alignment, and shall demonstrate that rather arbitrarily shaped grains exhibit helicity when they interact with gaseous flows and radiative fluxes.
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