太阳散射偏振性质研究

发布时间：2018-03-22 21:23

本文选题：偏振-太阳　切入点：汉勒效应-太阳　出处：《中国科学院研究生院（云南天文台）》2014年硕士论文　论文类型：学位论文

【摘要】：太阳磁场的诊断对研究太阳物理有着重要的意义。而磁场的诊断通常通过塞曼效应利用斯托克斯参量I，Q，U，和V对磁场进行反演。塞曼效应对通常只能对强磁场的进行诊断，而太阳宁静区存在的大量弱磁场很难被直接诊断。近几十年来大量科学家进行着利用汉勒效应（Hanle efect）诊断弱磁场的研究。而利用汉勒效应诊断弱磁场需要对偏振的产生机制有一个完整的理解。直到近年来，利用对偏振的测量精度达到105ZIMPOL（ZurichImaging Polarimeter）技术获得以斯托克斯Q/I表征的第二太阳光谱（Secondsolar Spectrum）展现丰富的散射偏振特征，促使了对偏振研究的蓬勃发展。通过对第二太阳光谱的研究，可以使我们对偏振产生机制理解的更为透彻，从而使利用汉勒效应诊断弱磁场逐渐成为可能。主要介绍了用量子电动力学为基础的密度矩阵来研究偏振光谱产生的物理过程。我们使用的是由E.LandiDegl’Innocenti在平直光谱近似下得到的公式。我们采用了7个原子能级的Mg原子模型，研究了MgI b线由散射产生的偏振轮廓Q/I和U/I在磁场中的变化。MgI b线非常适合用来研究下能级的汉勒效应，对亚高斯的磁场非常敏感，没有考虑部分频率再分布以及辐射转移所带来的影响。研究的结果显示MgI三线结构的Q/I和U/I轮廓对磁场的敏感范围分为两段，由下能级汉勒效应主导的0.001高斯到0.1高斯，有上能级汉勒效应主导的1高斯到10高斯。在下能级汉勒效应主导的磁场范围内，我们发现b4线的偏振度随着磁场强度的增加而增加，这是由于各个能级的原子能级排列分量（atomic alignment）都通过统计平衡方程耦合在一起，致使下能级的原子的排列分量的变化对上能级的原子的排列分量有一定想。因此虽然b4线的下能级J为零没有原子能级的排列分量，但是由于其他能级的反馈而使得上能级的排列分量发生变化导致偏振度增加，使b4线的偏振度随磁场强度的增加而增加。研究结果表明，由邻边昏暗效应所得到的不对称因子（anisotropy factor）不适合用来处理如Mg I b线等强线的谱线轮廓。连续谱可以十分明显的改变谱线的展宽。为了得到与观测结果相吻合的MgI b谱线轮廓必须要考虑二向色性。MgI b线十分适合用来研究下能级极化的汉勒效应，并且对亚高斯范围的磁场十分敏感非常适合用来诊断色球宁静区的极弱磁场，另外汉勒效应不仅可以退偏振还可以使偏振度增加。
[Abstract]:The diagnosis of the solar magnetic field is of great significance to the study of solar physics, and the diagnosis of the magnetic field usually uses the Stokes parameter I _ (Q) _ (U) and V to invert the magnetic field by Zeeman effect, which is usually only used to diagnose the strong magnetic field. In recent decades, a large number of scientists have studied the use of Hanle effect to diagnose weak magnetic field. The use of Hanle effect to diagnose weak magnetic field requires the polarization of the weak magnetic field. The mechanism of production has a complete understanding. Until recent years, The second solar spectrum (second solar spectrum), characterized by Stokes Q / I, was obtained by using the 105ZIMPOL(ZurichImaging Polarimeter technique, which promoted the development of polarization research. That will give us a better understanding of the mechanism of polarization generation, This makes it possible to diagnose the weak magnetic field by using the Hanler effect. This paper mainly introduces the density matrix based on quantum electrodynamics to study the physical process of polarized light spectrum. We use E.LandiDegl'Innocenti near the flat spectrum. We use seven atomic mg atomic models. The variation of polarization profile Q / I and U / I produced by scattering in magnetic field. MgIb line is very suitable for studying the lower energy level of Hamler effect, which is very sensitive to the magnetic field of sub#china_person0#. The results of the study show that the sensitivity range of Q / I and U / I profiles of MgI three-wire structure to magnetic field is divided into two segments, 0.001 Gao Si and 0.1 Gao Si, which are dominated by the lower energy level Hanler effect. In the magnetic field range dominated by the lower energy level Hansel effect, we find that the polarization degree of the b4 line increases with the increase of the magnetic field intensity. This is because atomic atomic alignment components of each energy level are coupled by statistical equilibrium equations. The change of the permutation components of the atoms of the lower energy level has a certain effect on the permutation components of the atoms of the upper energy level. Therefore, although the lower energy level J of the b4 line is zero, there is no atomic level permutation component. However, due to the feedback from other energy levels, the polarization degree of the upper energy level increases, and the polarization of the b4 line increases with the increase of the magnetic field intensity. The asymmetric factor derived from the adjacent dim effect is not suitable for dealing with the line profiles of strong lines such as the MgIb line. The continuous spectrum can obviously change the broadening of the spectral lines. The outline of MgI b line must consider the dichroism. MgIb line is very suitable for studying the Hansel effect of lower level polarization. Moreover, it is very sensitive to the magnetic field in the range of sub-#china_person0# and is suitable for diagnosing the extremely weak magnetic field in the quiet region of the color sphere. In addition, the Hanler effect can not only depolarization but also increase the degree of polarization.
【学位授予单位】：中国科学院研究生院（云南天文台）
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P182

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