3D Polarized Imaging of Coronal Mass Ejections: Chirality of a CME
3D Polarized Imaging of Coronal Mass Ejections: Chirality of a CME
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DOI：
10.3847/1538-4357/aa94ca
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发表时间：
2017-11
期刊：
影响因子：
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通讯作者：
Craig E. DeForest;C. A. D. Koning;H. Elliott
中科院分区：
文献类型：
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作者：
Craig E. DeForest;C. A. D. Koning;H. Elliott
我们报告了日冕物质抛射 (CME) 手性的直接偏振测定，利用汤姆逊散射物理原理应用于日地关系天文台/COR2 日冕仪的天气偏振图像。我们使用 ACE 航天器对同一 CME 进行原位磁场测量，证实了这一确定。 CME 手性与日冕喷射的螺旋度以及 CME 中夹带的质量和场有关。它对于预测 CME 磁场中与空间天气相关的 Z 分量也很重要。因此，CME 手性的远程测量是理解 CME 物理和预测单个 CME 地球效应的重要一步。汤姆逊散射的偏振特性众所周知，原则上可用于测量日冕和内日球层中成像物体的 3D 结构。然而，将该原理简化为实践受到背景扣除和日冕仪数据信噪比的双重困难的限制。 3D 结构的有用测量需要在 K 日冕的每个线性偏振分量中进行百分之几精度水平的相对光度测量。这对应于减去 F 日冕和相关信号之前天空直接图像中 10−4 级的相对光度精度。我们的测量得益于信号处理领域的最新发展，能够更好地将光度信号与天气 COR2 数据中的噪声分离。我们讨论了该演示测量与未来仪器要求以及日冕物质抛射和其他太阳风特征中 3D 结构的未来测量的相关性。
We report on a direct polarimetric determination of the chirality of a coronal mass ejection (CME), using the physics of Thomson scattering applied to synoptic polarized images from the Solar Terrestrial Relations Observatories/COR2 coronagraph. We confirmed the determination using in situ magnetic field measurements of the same CME with the ACE spacecraft. CME chirality is related to the helicity ejected from the solar corona along with the mass and field entrained in the CME. It is also important to prediction of the space-weather-relevant Z component of the CME magnetic field. Hence, remote measurement of CME chirality is an important step toward both understanding CME physics and predicting geoeffectiveness of individual CMEs. The polarimetric properties of Thomson scattering are well known and can, in principle, be used to measure the 3D structure of imaged objects in the solar corona and inner heliosphere. However, reduction of that principle to practice has been limited by the twin difficulties of background subtraction and the signal-to-noise ratio in coronagraph data. Useful measurements of the 3D structure require relative photometry at a few percent precision level in each linear polarization component of the K corona. This corresponds to a relative photometric precision of order 10−4 in direct images of the sky before subtraction of the F corona and related signal. Our measurement was enabled by recent developments in signal processing, which enable a better separation of the photometric signal from noise in the synoptic COR2 data. We discuss the relevance of this demonstration measurement to future instrument requirements, and to the future measurements of 3D structures in CMEs and other solar wind features.