论文标题
基于Helios和Parker太阳能探针观测的内层中鞘间冠状质量弹出的鞘和前缘结构的特征和进化
Characteristics and evolution of sheath and leading edge structures of interplanetary coronal mass ejections in the inner heliosphere based on Helios and Parker Solar Probe observations
论文作者
论文摘要
目的：我们从统计学上研究了星际冠状质量弹出（ICMES）的上游区域的血浆和磁场特征，它们作为内层中距离太阳的距离的函数。我们使用来自Helios 1/2（0.3-1AU）的40个观察到的ICME的样本，来自Parker太阳能探针（0.32-0.75AU）的样本。对于每个事件，我们都会确定四个主要密度结构，即冲击，护套，前缘（LE）和磁性喷射（ME）本身。方法：我们为每个结构平均等离子体和磁场参数值以及持续时间分别得出，并将结果与上游太阳风（SW）进行比较，以研究不同密度结构之间的相互关系。结果：由于冲击后湍流的SW材料，鞘结构可能由压缩等离子体组成。鞘位于压缩环境SW的区域前，LE通常直接在磁驱动器的前面发现，并且似乎与CME的遥感观测值中通常观察到的明亮前沿相匹配。与周围SW相比，鞘在约0.06AU上变得更密集，我们将其解释为实际护套形成的平均起始距离。在0.09-0.28AU之间，鞘结构密度在ME内的密度上开始占主导地位。 ME密度似乎低于0.45-1.07au的环境SW密度。除了众所周知的ME膨胀外，鞘尺的大小还显示出与距离的较弱的正相关，而LE似乎并没有随着距离太阳的距离而扩展。我们进一步发现，ICME冲击上游的鞘密度与局部SW等离子体速度之间的抗相关性中等。经验关系被得出，将环境SW速度与鞘和LE密度连接起来，该速度可用于建模ICME进化。给出了这些结果的限制。
Aims: We statistically investigate the plasma and magnetic field characteristics of the upstream regions of interplanetary coronal mass ejections (ICMEs) and their evolution as function of distance to the Sun in the inner heliosphere. We use a sample of 40 well-observed ICMEs from Helios 1/2 (0.3-1au) and 5 from Parker Solar Probe (0.32-0.75au). For each event we identify four main density structures, namely shock, sheath, leading edge (LE), and magnetic ejecta (ME) itself. Methods: We derive separately for each structure averaged plasma and magnetic field parameter values as well as duration and place the results into comparison with the upstream solar wind (SW) to investigate the interrelation between the different density structures. Results: The sheath structure presumably consists of compressed plasma due to the turbulent SW material following the shock. The sheath lies ahead of a region of compressed ambient SW, the LE, which is typically found directly in front of the magnetic driver and seems to match the bright leading edge commonly observed in remote sensing observations of CMEs. The sheath becomes denser than the ambient SW at about 0.06au, which we interpret as the average starting distance for actual sheath formation. Between 0.09-0.28au the sheath structure density starts to dominate over the density within the ME. The ME density seems to fall below the ambient SW density over 0.45-1.07au. Besides the well-known expansion of the ME, the sheath size shows a weak positive correlation with distance, while the LE seems not to expand with distance from the Sun. We further find a moderate anti-correlation between sheath density and local SW plasma speed upstream of the ICME shock. An empirical relation is derived connecting the ambient SW speed with sheath and LE density that can be used for modeling of ICME evolution. Constraints to those results are given.
