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arXiv 2402.04282physics.space-ph
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行星际磁场 $B_y$ 控制在日冕物质抛射遭遇期间地球的阿尔芬翼

Interplanetary magnetic field $B_y$ controlled Alfvén wings at Earth during encounter of a coronal mass ejection

Yuxi Chen, Chuanfei Dong, Li-Jen Chen, Menelaos Sarantos, Brandon L. Burkholder

AI总结:

本研究通过全球MHD模拟,发现2023年4月ICME事件使太阳风转为亚阿尔芬状态,形成受IMF By控制的阿尔芬翼,并揭示了其磁场、流场及电流结构,深化了对磁化体与亚阿尔芬风相互作用的理解。

摘要:

在地球轨道附近,典型的太阳风阿尔芬马赫数超过5,超阿尔芬太阳风驱动着传统的磁层结构。然而,在行星际日冕物质抛射(ICME)事件的抛射物阶段,由于行星际磁场(IMF)强度增强和密度降低,阿尔芬马赫数可能显著减小。2023年4月24日,一次ICME到达地球轨道。太阳风密度降至低至0.3 amu/cc,而IMF强度约为25 nT。因此,太阳风流转变为亚阿尔芬状态,阿尔芬马赫数为0.4,为研究行星磁层与低马赫数太阳风的相互作用提供了机会。我们进行了全球模拟,以研究地球磁层对亚阿尔芬ICME抛射物的响应。全球磁流体动力学(MHD)模拟结果显示,随着太阳风变为亚阿尔芬,阿尔芬翼形成。此外,亚阿尔芬时期以IMF By分量占主导为特征,导致阿尔芬翼向晨侧和昏侧延伸。在本文中,我们展示了阿尔芬翼周围的磁场、等离子体流和电流系统的结构。深入讨论了亚阿尔芬太阳风条件下的全球磁层对流。我们的结果达到了对磁化天体与亚阿尔芬上游条件相互作用的新理解水平,并为未来的观测提供了指导。

英文摘要:

In the vicinity of Earth's orbit, the typical solar wind Alfvén Mach number exceeds 5, and the super-Alfvénic solar wind drives a conventional magnetosphere configuration. However, at the ejecta phase of an interplanetary coronal mass ejection (ICME) event, the Alfvén Mach number may experience a significant reduction due to the intensified interplanetary magnetic field (IMF) strength and decreased density. On 24 April 2023, an ICME reached Earth's orbit. The solar wind density dropped to as low as 0.3 amu/cc while the IMF strength is about 25 nT. As a result, the solar wind flow transitions to a sub-Alfvénic state with an Alfvén Mach number of 0.4, providing opportunities to investigate the interaction of planetary magnetospheres with low Mach number solar wind. We carry out global simulations to investigate the responses of Earth's magnetosphere to the sub-Alfvénic ICME ejecta. The global magnetohydrodynamic (MHD) simulation results show the formation of Alfvén wings as the solar wind becomes sub-Alfvénic. Furthermore, the sub-Alfvénic period was characterized by the dominance of IMF By component, causing the Alfvén wings to extend towards the dawn and dusk sides. In this paper, we present the structures of the magnetic field, plasma flow, and current system around the Alfvén wings. The global magnetospheric convection under the sub-Alfvénic solar wind condition is discussed in depth. Our results achieve a new level of understanding about the interaction between a magnetized body and sub-Alfvénic upstream conditions, and provide guidance for future observations.

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。

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