Spectro-Imaging Polarimetry of the Local Corona During Solar Eclipse

Abstract

Results are presented from spectro-imaging polarimetry of radiation from the local solar corona during the 2013 total solar eclipse in Gabon. This polarimetric observation was performed from 516.3 nm to 532.6 nm using a prototype Fiber Arrayed Solar Optical Telescope (FASOT). A polarimetric noise level on the order of 10 −3 results from a reduced polarimetric optical switching demodulation (RPOSD) procedure for data reduction. It is revealed that the modality of fractional linear polarization profiles of the green coronal line shows a diversity, which may indicate complex mechanisms. The polarization degree can approach 3.2 % above the continuum polarization level on a scale of 1500 km, and the nonuniform spatial distribution in amplitude and polarization direction is found even within a small field of view of 7500 km. All of this implies that the coronal polarization is highly structured and complex even on a small scale.

Observations of the solar corona during the total solar eclipse on 21 August 2017

“…It has also been demonstrated that the Hanle effect, a process involving modification of polarization by magnetic fields, could be powerful to diagnose the weak magnetic fields in the upper solar atmosphere (e.g., Trujillo Bueno et al, 2002; Li H et al, 2017). All these techniques require a precise measurement of polarization of coronal emission lines (e.g., Qu ZQ et al, 2009, 2017). Thanks to the greatly reduced level of scattered light, the 2017 total solar eclipse provided an excellent opportunity for such a measurement.…”

COronal Magnetism and Plasma ASsembled Scopes(COMPASS)

“…(3) 观测目标对仪器参数设计和谱线选择的约束. 这两束光同时测量构成偏振光学开光 [32,33] 操作的基 础. 对波片起始位置以及围绕主光轴转动角度进行优 化, 可以获得合理的偏振测量效率的分配 [56] .…”

“…对波片起始位置以及围绕主光轴转动角度进行优 化, 可以获得合理的偏振测量效率的分配 [56] . 为了提 高偏振测量灵敏度同时又要考虑不降低时间分辨率, 我们需要进行简化偏振光学开关操作 [33] . 特点可能对望远镜弯程产生的影响, 初步采用Serrur-ier桁架结构 [57] .…”

“…这是因为如果粒子带有净电荷或具有一定的磁 矩, 处于磁场中产生的辐射就会受其影响. 宏观上, 自 由带电粒子会产生回旋辐射, 可以通过射电观测提取 磁场信息 [30] ; 而微观上, 磁场可以使原子或离子的能 [32,33] 来降低大气视宁度变化以及仪器制造非完美 性产生的噪声. 为了获得足够的偏振测量精度, 还需要 定时输入标准的偏振信号作为校正源对测量进行偏振 校正.…”

A Novel Scanning Method Applied to New-Style Solar Telescope Based on Autoguiding System

“…Due to the compact and symmetrical optics configuration of FASOT up to the polarization modulator, the additional polarization from instrument is minimized. On the other hand, a novel polarization demodulation technique named reduced optical switching demodulation [4] is adopted by FASOT to improve the polarimetric sensitivity and reduce the integration time. These technologies mentioned above will make FASOT obtain a polarimetric noise level on the order of 8.0 × 10 −4 .…”