Combining white light and UV Lyman-alpha coronagraphic images to determine the solar wind speed. The quick inversion method
Combining white light and UV Lyman-alpha coronagraphic images to determine the solar wind speed. The quick inversion method
复制标题
结合白光和紫外线莱曼阿尔法日冕图像来确定太阳风速。
DOI：
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发表时间：
2021
影响因子：
6.5
通讯作者：
F. Frassati
中科院分区：
文献类型：
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作者：
A. Bemporad;S. Giordano;L. Zangrilli;F. Frassati
上下文。从空间获取的不同波长间隔的多通道日冕图像的可用性将为我们提供一个新的视角，使我们能够研究许多等离子体物理参数的二维分布和时间演化，如等离子体密度、温度和出射ff低速。目标。这项工作的重点是结合白光(WL)和紫外线(Lyα)日冕图像来演示直接利用这两幅图像的比率来测量内日冕太阳风速的能力(一种称为快速反演法的技术)，从而避免了在数据反演中必须考虑视线(LOS)积分等因素。方法：研究方法。在推导了快速反演法的理论基础和主要假设的基础上，首先用一维径向解析程序检验了数据反演技术，然后用三维数值磁流体力学模拟方法对其进行了检验，以显示与太阳活动周期不同阶段有关的变化以及等离子体参数的复杂的fi分布。同样的技术也适用于从SOHO UVCS和LASCO仪器在太阳活动周期的最小和最大值附近获得的真实数据获得的平均WL和UV图像。结果。输入和输出速度之间的比较显示出总体上很好的一致性，表明这种方法可以用WL-UV图像比率来推断太阳风速，可以补充需要完全LOS积分的更复杂的技术。这里描述的分析还使我们能够量化Outflow速度中可能的误差，并确定快速反演法执行得最好的日冕区域。对真实的UVCS和LASCO数据进行的快速反演也使我们能够重建太阳极小期快风和慢风的典型双峰分布，并得出太阳极大值附近更复杂的图像。结论。本文所述技术的应用将对未来用多通道WL和UV(Lyα)日冕仪获取的数据进行分析非常重要，例如太阳轨道器上的METIS、ASO-S上的LST以及任何其他未来的WL和UV(Lyα)多通道日冕仪。
Context. The availability of multi-channel coronagraphic images in di ff erent wavelength intervals acquired from the space will provide a new view of the solar corona, allowing us to investigate the 2D distribution and time evolution of many plasma physical parameters, such as plasma density, temperature, and outflow speed. Aims. This work focuses on the combination of white light (WL) and UV (Ly α ) coronagraphic images to demonstrate the capability of measuring the solar wind speed in the inner corona directly with the ratio of these two images (a technique called the quick inversion method), thus avoiding having to account for the line-of-sight (LOS) integration e ff ects in the inversion of data. Methods. After a derivation of the theoretical basis and illustration of the main hypotheses in the quick inversion method, the data inversion technique is tested first with 1D radial analytic profiles and then with 3D numerical MHD simulations in order to show the e ff ects of variabilities related to di ff erent phases of the solar activity cycle and the complex LOS distribution of plasma parameters. The same technique is also applied to average WL and UV images obtained from real data acquired by the SOHO UVCS and LASCO instruments around the minimum and maximum of the solar activity cycle. Results. Comparisons between input and output velocities show a good agreement overall, demonstrating that this method, which allowed us to infer the solar wind speed with the WL-to-UV image ratio, can be complementary to more complex techniques requiring the full LOS integration. The analysis described here also allowed us to quantify the possible errors in the outflow speed, and to identify the coronal regions where the quick inversion method performs at the best. The quick inversion applied to real UVCS and LASCO data also allowed us to reconstruct the typical bimodal distribution of fast and slow wind at solar minimum, and to derive a more complex picture around the solar maximum. Conclusions. The application of the technique shown here will be very important for the future analyses of data acquired with multi- channel WL and UV (Ly α ) coronagraphs, such as Metis on board the Solar Orbiter, LST on board ASO-S, and any other future WL and UV Ly α multi-channel coronagraphs.