A classical theory of coronal emission line polarization
A classical theory of coronal emission line polarization
复制标题
DOI：
10.1086/309499
复制
发表时间：
2000-10-10
影响因子：
4.9
通讯作者：
Casini, R
中科院分区：
文献类型：
--
作者：
Lin, HS;Casini, R
我们提出了磁化日冕中极化磁偶极发射线形成的经典理论。由于禁戒线的爱因斯坦A系数较小，以及日冕中的预期磁场强度，不同磁子态之间的相干可以忽略不计，因此这些禁戒线的观测到的斯托克斯矢量是跃迁上能级各个磁子态去激发时发射的斯托克斯矢量非相干叠加的结果。利用经典电动力学和弱场展开形式，我们可以推导出无碰撞区J=1到J=0跃迁的主要极化性质。特别地，我们推导了由光球的各向异性、非偏振照明以及斯托克斯Q和U线偏振对天空平面内磁场方向的依赖所引起的原子在上能级中的正确排列量。原子排列对V分布的影响也得到了正确的再现。这项工作对辐射离子中产生原子取向的物理过程以及共振-散射线极化中相关的Van Vleck效应和取向对塞曼效应圆极化的贡献提供了经典的解释。
We present a classical theory of formation for polarized, magnetic dipole emission lines in the magnetized solar corona. Because of the small Einstein A-coefficients of forbidden lines and the expected magnetic field strengths in the corona, coherences between different magnetic substates can be neglected, so the observed Stokes vector for these lines is the result of the incoherent superposition of the Stokes vectors emitted in the de-excitation of the individual magnetic substates of the transition's upper level. Using classical electrodynamics and a weak-field expansion formalism, we could derive the main polarization properties of the transition J = 1 to J = 0, in the collisionless regime. In particular, we derived the correct amount of atomic alignment in the upper level, induced by the anisotropic, unpolarized illumination from the photosphere, and the dependence of Stokes Q and U linear polarization on the magnetic field direction in the plane of the sky. The influence of atomic alignment on the V profile is also correctly reproduced. This work provides a classical interpretation of the physical process that generates atomic alignment in the radiating ion and how the associated Van Vleck effect in resonance-scattering linear polarization and the alignment contribution to Zeeman effect circular polarization come about.