Tracking Nonradial Outflows in Extreme Ultraviolet and White Light Solar Images
Tracking Nonradial Outflows in Extreme Ultraviolet and White Light Solar Images
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DOI：
10.3847/1538-4357/acba08
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
N. Alzate;H. Morgan;S. Di Matteo
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文献类型：
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作者：
N. Alzate;H. Morgan;S. Di Matteo
了解日冕需要了解其各个层的动态以及随后与日光层的连接性。这需要理解流出的性质和通过中间日冕（1.5-6.0 R s）的物理转变。虽然这一区域仍然无法进行现场测量，但遥感观测是可用的，但由于视线效应和靠近太阳（≤3.0 R s）的流出结构的非径向运动，它们的解释可能存在争议。在这项工作中，我们描述了一种方法，以减轻这些挑战，通过使用先进的图像处理技术生成非径向高度-时间曲线的流出。在2008年太阳活动极小期期间，在STEREO/SECCHI太阳图像中确定了一个大型赤道流光的北方和南方边界，使用基于亮度阈值和分段多项式函数拟合的两种不同方法。为了解决视线问题，我们使用了基于SECCHI/COR 2图像的日冕电子密度3D分布的断层重建。的流光边界的位置角的时间序列的谱分析显示其振荡性质在某些高度在36-48和10.5-14.6小时。划分之间的距离北方和南方流光边界在每个高度的相等部分，我们得到的非径向高度-时间路径，我们产生的非径向轮廓的日冕/太阳风等离子体流出。我们跟踪了从EUVI的太阳不间断地流出，通过COR 1进入COR 2。最后，我们讨论了日冕物质抛射和两个小尺度特征的非径向天平面速度的初步结果。
Understanding the solar corona requires knowledge of its dynamics through its various layers and subsequent connectivity to the heliosphere. This requires understanding the nature of the outflows and the physical transitions through the middle corona (∼1.5–6.0 R s ). While this region is still inaccessible to in situ measurements, remote sensing observations are available, but their interpretation can be controversial due to line-of-sight effects and the nonradial motion of outflowing structures close to the Sun (≤3.0 R s ). In this work, we describe a method to mitigate these challenges by generating nonradial height–time profiles of outflows by using advanced image processing techniques. The northern and southern boundaries of a large equatorial streamer during the 2008 solar minimum were identified in STEREO/SECCHI solar images, using two different methodologies based on thresholds of brightness and piecewise polynomial function fitting. To address line-of-sight issues, we used tomographic reconstruction of the 3D distribution of the coronal electron density based on SECCHI/COR2 images. Spectral analysis of the time series of the position angle of the streamer boundary revealed its oscillatory nature at some heights at 36–48 and 10.5–14.6 hr. Dividing the distance between the northern and southern streamer boundaries in equal parts at each height, we obtained nonradial height–time paths from which we generated nonradial profiles of corona/solar wind plasma outflow. We tracked outflows as they moved uninterruptedly from the Sun in EUVI, through COR1 and into COR2. Finally, we discuss the preliminary results of nonradial plane-of-sky velocities for a coronal mass ejection and two small-scale features.