论文标题
ICME护套中的小型通量绳
Small-scale flux ropes in ICME sheaths
论文作者
论文摘要
当由于ICME的传播和膨胀而偏转和压缩时，会形成星际冠状质量弹出（ICME）的鞘区域。因此，在太阳风中发现的小规模通量绳索可以扫入ICME驱动的护套区域。它们也可以通过一系列过程在鞘内本地生成。这项工作应用了小波分析，以获得归一化的磁性螺旋，归一化的交叉螺旋和归一化剩余能量，并利用它们在55个ICME驱动的鞘内区域中识别小规模的通量绳索和Alfvén波，在近油气太阳能风中风速器上观察到的。它们的出现分别研究了$ 10^{ - 2} -10^{ - 4} $ Hz之间的三个不同频率范围。我们发现，小规模通量绳在ICME鞘中比上游风更常见，这意味着它们至少在某种程度上是在鞘中积极产生的，而不仅仅是从上游风中压缩。在上游的风和鞘中，Alfvén波更均匀地发生。这项研究还表明，虽然最高的频率（最小）通量绳在整个护套上相对均匀地发生，但较低的频率（最大尺度）通量绳峰附近的ICME前缘峰。这表明它们可能具有不同的物理起源，而在ICME领先优势附近的过程对于产生较大规模的人群很重要。
Sheath regions of interplanetary coronal mass ejections (ICMEs) are formed when the upstream solar wind is deflected and compressed due to the propagation and expansion of the ICME. Small-scale flux ropes found in the solar wind can thus be swept into ICME-driven sheath regions. They may also be generated locally within the sheaths through a range of processes. This work applies wavelet analysis to obtain the normalized reduced magnetic helicity, normalized cross helicity, and normalized residual energy, and uses them to identify small-scale flux ropes and Alfvén waves in 55 ICME-driven sheath regions observed by the Wind spacecraft in the near-Earth solar wind. Their occurrence is investigated separately for three different frequency ranges between $10^{-2} - 10^{-4}$ Hz. We find that small scale flux ropes are more common in ICME sheaths than in the upstream wind, implying that they are at least to some extent actively generated in the sheath and not just compressed from the upstream wind. Alfvén waves occur more evenly in the upstream wind and in the sheath. This study also reveals that while the highest frequency (smallest scale) flux ropes occur relatively evenly across the sheath, the lower frequency (largest scale) flux ropes peak near the ICME leading edge. This suggests that they could have different physical origins, and that processes near the ICME leading edge are important for generating the larger scale population.
