Multipoint Observations of the Dynamics at an ICME Sheath–Ejecta Boundary
Multipoint Observations of the Dynamics at an ICME Sheath–Ejecta Boundary
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DOI：
10.3847/1538-4357/acf99e
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发表时间：
2023-10
期刊：
影响因子：
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通讯作者：
M. Ala‐Lahti;Tuija Pulkkinen;J. Ruohotie;M. Akhavan-Tafti;S. Good;E. Kilpua
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文献类型：
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作者：
M. Ala‐Lahti;Tuija Pulkkinen;J. Ruohotie;M. Akhavan-Tafti;S. Good;E. Kilpua
行星际日冕物质抛射(ICME)的径向演化依赖于它们与周围介质的相互作用，这会导致ICME侵蚀并影响其地球效率。本文对2020年4月20日1Au的ICME进行了多点研究，分析了ICME的前沿边界，该边界将受限喷出物与上游混合的相互作用的鞘喷出等离子体分开。在该边界上观察到了一个分叉的电流片、高度丝状流和一股双侧喷流。首次记录到的磁剪切角为40°的双面喷流暗示了与ICME侵蚀有关的多个(斑块状)重联地点。重联废气具有精细的结构，包括多步磁场旋转和局域结构，只有在航天器间间隔为0.4-1.6RE的单独的星团航天器才能测量到这些结构。边界上游的混合等离子体与0.8Au的前驱物质在1Au缺乏相干性，并在41-237RE(114RE)的径向(横向)距离上表现出向南磁场的显著变化。这种不一致性表明，需要在太阳风的多个地点进行连续(亚)秒分辨率的等离子体和现场测量，以充分处理洲际海洋生态系统的时空结构，并产生准确的空间天气预报。
The radial evolution of interplanetary coronal mass ejections (ICMEs) is dependent on their interaction with the ambient medium, which causes ICME erosion and affects their geoefficiency. Here, an ICME front boundary, which separates the confined ejecta from the mixed, interacted sheath–ejecta plasma upstream, is analyzed in a multipoint study examining the ICME at 1 au on 2020 April 20. A bifurcated current sheet, highly filamented currents, and a two-sided jet were observed at the boundary. The two-sided jet, which was recorded for the first time for a magnetic shear angle <40°, implies multiple (patchy) reconnection sites associated with the ICME erosion. The reconnection exhaust exhibited fine structure, including multistep magnetic field rotation and localized structures that were measured only by separate Cluster spacecraft with the mission inter-spacecraft separation of 0.4–1.6 R E. The mixed plasma upstream of the boundary with a precursor at 0.8 au lacked coherency at 1 au and exhibited substantial variations of southward magnetic fields over radial (transverse) distances of 41–237 R E (114 R E). This incoherence demonstrates the need for continuous (sub)second-resolution plasma and field measurements at multiple locations in the solar wind to adequately address the spatiotemporal structure of ICMEs and to produce accurate space weather predictions.