arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1502.05112astro-ph.SRphysics.plasm-phphysics.space-ph
收藏

用速度修正的圆柱形无力磁绳模型研究1 AU磁云的等离子体运动

Investigating plasma motion of magnetic clouds at 1 AU through a velocity-modified cylindrical force-free flux rope model

Yuming Wang, Zhenjun Zhou, Chenglong Shen, Rui Liu, S. Wang

摘要:

磁云(MC)是行星际日冕物质抛射(CME)的对应物,通常用通量绳模拟。通过假设磁链的准定常演化和自相似展开,我们在圆柱形无力磁链绳模型中引入了三种类型的整体运动,发展了一种新的磁链的速度修正模型。三种类型的全球运动是远离太阳的线性传播运动,膨胀运动和相对于MC轴的极向运动。将该模型应用于72个由Wind卫星观测到的MCs,研究了MCs的等离子体运动特性。首先,我们发现一些MC有一个显着的传播速度垂直于径向方向,这表明CME的偏转传播和/或在行星际空间旋转的直接证据。其次,我们证实了以前的结果,膨胀速度与径向传播速度相关,大多数MCs在1 AU时没有自相似膨胀。在我们的统计中,大约有62%/17%的MCs在1AU时经历了欠膨胀/过膨胀,平均膨胀率约为0.6。第三,最有趣的是,我们发现,一个显着的极向运动确实存在于一些MC。因此,提出了关于极向运动原因的三种推测。这些发现推进了我们对MC在1 AU处的性质以及CME从太阳到行星际空间的动态演化的理解。

英文摘要:

Magnetic clouds (MCs) are the interplanetary counterparts of coronal mass ejections (CMEs), and usually modeled by a flux rope. By assuming the quasi-steady evolution and self-similar expansion, we introduce three types of global motion into a cylindrical force-free flux rope model, and developed a new velocity-modified model for MCs. The three types of the global motion are the linear propagating motion away from the Sun, the expanding and the poloidal motion with respect to the axis of the MC. The model is applied to 72 MCs observed by Wind spacecraft to investigate the properties of the plasma motion of MCs. First, we find that some MCs had a significant propagation velocity perpendicular to the radial direction, suggesting the direct evidence of the CME's deflected propagation and/or rotation in interplanetary space. Second, we confirm the previous results that the expansion speed is correlated with the radial propagation speed and most MCs did not expand self-similarly at 1 AU. In our statistics, about 62\%/17\% of MCs underwent a under/over-expansion at 1 AU and the expansion rate is about 0.6 on average. Third, most interestingly, we find that a significant poloidal motion did exist in some MCs. Three speculations about the cause of the poloidal motion are therefore proposed. These findings advance our understanding of the MC's properties at 1 AU as well as the dynamic evolution of CMEs from the Sun to interplanetary space.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑