Polarization from Aligned Atoms as a Diagnostic of Circumstellar, Active Galactic Nuclei, and Interstellar Magnetic Fields. II. Atoms with Hyperfine Structure
Polarization from Aligned Atoms as a Diagnostic of Circumstellar, Active Galactic Nuclei, and Interstellar Magnetic Fields. II. Atoms with Hyperfine Structure
复制标题
对齐原子的极化作为星周、活动星系核和星际磁场的诊断。
DOI：
10.1086/510847
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
A. Lazarian
中科院分区：
文献类型：
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作者：
Huirong Yan;A. Lazarian
我们证明原子排列提供了一种研究天体物理磁场拓扑的可靠方法。原子排列的影响是由各向异性辐射通量泵浦的原子基态子能级的相对布居数的调制引起的。当这种排列的原子在外部磁场中进动时，这会影响由原子的散射和吸收引起的偏振辐射的特性。因此，发射线和吸收线的偏振取决于磁场的三维 (3D) 几何形状以及入射辐射的方向和各向异性。我们考虑具有超精细结构的天体物理学重要原子的子集。对于发射线，我们获得了线性偏振方向对磁场方向和入射泵浦辐射的依赖性。对于吸收线，我们在极化垂直和平行于磁场时建立。对于发射线和吸收线，我们发现偏振度与磁场 3D 几何形状的相关性。我们声称，原子排列为研究星周区域、活动星系核（AGN）以及行星际和星际介质的磁场提供了独特的工具。该工具允许人们研究磁场的 3D 拓扑并建立其他重要的天体物理参数。我们考虑稳定状态下的原子以及经历光子个体散射的原子所产生的偏振。我们通过考虑彗星尾迹中钠排列的情况来证明原子排列在天体物理磁场研究中的实用性。
We show that atomic alignment presents a reliable way to study the topology of astrophysical magnetic fields. The effect of atomic alignment arises from modulation of the relative population of the sublevels of the atomic ground state pumped by anisotropic radiation flux. As such aligned atoms precess in the external magnetic field, this affects the properties of the polarized radiation arising from both scattering and absorption by the atoms. As a result, the polarizations of emission and absorption lines depend on the three-dimensional (3D) geometry of the magnetic field as well as the direction and anisotropy of incident radiation. We consider a subset of astrophysically important atoms with hyperfine structure. For emission lines, we obtain the dependencies of the direction of linear polarization on the directions of the magnetic field and the incident pumping radiation. For the absorption lines we establish when the polarization is perpendicular and parallel to the magnetic field. For both emission and absorption lines we find the dependence on the degree of polarization on the 3D geometry of the magnetic field. We claim that atomic alignment provides a unique tool for studying magnetic fields in circumstellar regions, active galactic nuclei (AGNs), and the interplanetary and interstellar media. This tool allows one to study the 3D topology of magnetic fields and establish other important astrophysical parameters. We consider polarization arising from both atoms in the steady state and also those undergoing individual scattering of photons. We demonstrate the utility of atomic alignment for studies of astrophysical magnetic fields by considering a case of sodium alignment in a comet wake.