了解太阳大气的物理状态、化学组成和运动情况等信息，现在主要通过太阳光谱来得到。谱线是电子在原子内部结构体系的分立能级之间的跃迁形成的。太阳对外辐射，辐射与物质发生吸收，发射与散射相互作用，从而形成各种类型的谱线。在太阳的连续光谱中，叠加了大量的吸收线和发射线。这些吸收线和发射线形成于太阳大气的不同高度。它们有着不同的轮廓形状和强度。连续谱一般在较深处产生。吸收线和发射线主要形成于较外层大气。谱线从产生到我们观测到，在整个过程中会发生加宽。通过这些致宽效应的机制分析，我们可以得到谱线在产生和传递过程中的很多物理信息。这个过程是辐射转移，辐射在介质中的传播受到吸收、发射和散射过程的影响。辐射转移方程用数学方法描述了这些相互作用。我们分析这些过程来诊断太阳大气的谱线参数。本文给出了通过分析光纤阵列太阳光学望远镜(FASOT)原理样机在2013年加蓬日全食观测取得的Mg I b2闪耀光谱资料，发现谱线参数空间分布的不规则性。这些影响谱线轮廓的参数分别为：谱线源函数与连续谱源函数的比值β，线发射系数与连续谱发射系数比值ζ，连续吸收系数与线吸收系数的比值r0，线心不透明度τ0，多普勒展宽ΔλD，视线方向速度vlos。相比于这些谱线参量的空间分布，由观测得到的谱线积分强度和连续谱强度的空间分布呈现出近似球对称性。谱线参量的空间不规则分布源于谱线轮廓特征空间分布。这些谱线轮廓特征为最大谱线发射强度，谱线线宽和线心波长。此外，通过光谱分析，我们还发现线心不透明度τ0在中色球层也拥有大于1的值，这一点表明在这些层次是吸收仍然是不可忽略的。最后，我们证明了正确的温度不能从在这些层形成的谱线多普勒宽度导出，这是因为非局部热动平衡中粒子的随机运动速率分布偏离热运动的麦克斯韦速率分布理论。同时也是观测区域多个不可分辨的源合成的结果。本文主要科学意义在于得到了太阳中色球层的谱线参数分布。发现这些谱线参数呈现的不规则分布。我们对谱线的异常加宽的原因提出了解释。这可能有助于防止对太阳高层大气温度的错误诊断。
其他摘要
In order to understand the physical state, chemical composition and movement of the solar atmosphere information, now mainly through the solar spectrum. Lines are formed by transitions between discrete energy levels of electrons in the internal structural system of an atom. Solar external radiation, radiation and matter absorption, emission and scattering interaction, thus forming various types of spectral lines. In the continuous spectrum of the sun, a large number of absorption and emission lines are superimposed. These absorption and emission lines form at different altitudes in the solar atmosphere. They come in different contour shapes and strengths. Continuous spectra generally occur at deeper depths. Absorption and emission lines are mainly formed in the upper atmosphere. The line gets widened the whole time it's created until we observe it. Through the mechanism analysis of these broadening effects, we can get a lot of physical information during the generation and transmission of spectral lines. This process is radiation transfer, in which the propagation of radiation through a medium is affected by absorption, emission and scattering processes. Radiative transfer equations describe these interactions mathematically. We analyze these processes to diagnose spectral line parameters of the solar atmosphere.This paper presents the analytical results of solar Mg I b2 flash spectra, obtained by the prototype Fiber Arrayed Solar Optic Telescope (FASOT) in process of the 2013 Gabon total solar eclipse. The analysis reveals irregular distributions of the spectral line parameters like ratio of line source function to continuum one β, ratio of line emission to continuum emission ζ, ratio of the continuum absorption to the line absorption r0, line center opacity τ0, the line width ΔλD, and the line-of-sight velocity vlos, while the approximately spherical symmetry can be found in the maps of integrated line intensity and continuum intensity. These irregular distributions originate from those of line profile features like the maximum intensity, the line width and line center wavelength. It is also found from the recovered line center opacity τ0 that in the middle chromosphere, the opacity is not small due to non-ignorable absorption and the long light path along the line-of-sight. Finally, we demonstrate that the proper temperature cannot be derived from the Doppler width in these layers departed from thermodynamical equilibrium since the distribution of random motion speed of particles cannot be described by Maxwellian one. And we show that the excessive broadening of spectral lines can be due to co-existence of multiple radiative sources with different line-of-sight velocities unresolved in one detector pixel.The main scientific significance of this paper is to obtain the spectral line parameter distribution of the chromosphere in the sun. The irregular distribution of these spectral line parameters was found. We propose an explanation for the abnormal broadening of spectral lines. This could help prevent false diagnoses of the temperature of the sun's upper atmosphere.
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