Linear polarization of radio frequency lines in molecular clouds and circumstellar envelopes
Linear polarization of radio frequency lines in molecular clouds and circumstellar envelopes
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分子云和星周包层中射频线的线性偏振
DOI：
10.1086/159663
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
N. Kylafis
中科院分区：
文献类型：
--
作者：
P. Goldreich;N. Kylafis
我们预测，星际线具有百分之几的线性偏振提供的光学深度在源区域是各向异性的和统一的顺序和辐射率至少是可比的碰撞率。这些条件预期在许多发射无线电和远红外线辐射的源中得到满足。在塞曼分裂
超过辐射率和碰撞率，则线偏振平行于或垂直于磁场在天空平面上的投影。这种“强磁场”极限预计适用于所有的射频线和许多远红外线，这些线形成于磁矩与玻尔磁子相当的能级之间。“弱磁场”极限与大多数远红外线有关，这些线形成于磁矩为核磁子量级的能级之间。在这个极限中，偏振方向由传播方向相对于各向异性光学深度的取向确定。
We predict that interstellar lines possess a few percent linear polarization provided that the optical depth in the source region is both anisotropic and of order unity and the radiative rates are at least comparable to the collision rates. These conditions are expected to be met in many sources which emit radio and far-infrared line radiation. Under circumstances in which the Zeeman splitting
exceeds both the radiative and collisional rates the linear polarization is aligned either parallel or perpendicular to the projection of the magnetic field on the plane of the sky. This "strong magnetic field" limit is expected to apply to all radio frequency lines and to many of those far infrared lines which form between levels whose magnetic moments are comparable to the Bohr magneton. The "weak magnetic field" limit is relevant to most far-infrared lines formed between levels with magnetic moments of order the nuclear magneton. In this limit the polarization direction is determined by the orientation of the propagation direction with respect to the anisotropic optical depth.