Magnetotail Ion Acceleration in 3‐D Global Hybrid Simulations
Magnetotail Ion Acceleration in 3‐D Global Hybrid Simulations
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DOI：
10.1029/2022ja030980
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
F. Shi;Zhifan Guo;Yu Lin;Xueyi Wang;Lei Cheng
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文献类型：
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作者：
F. Shi;Zhifan Guo;Yu Lin;Xueyi Wang;Lei Cheng
磁尾重联注入粒子在磁层物理中起着重要的作用，因为这些粒子可以在磁层内部加速形成高能的含能粒子。在本文中，我们用ANGIE3D进行了三维全球混合模拟，从近地重联区到内磁层自洽地追踪了这种离子粒子，并证明了向地球的快速流动在尾部等离子体片中离子加速过程中的重要作用。虽然粒子可以从重联X线区获得数倍于其初始能量的能量，但由于它们与向地球的快速流相遇，离子能量在很短的时间内发生了急剧的增加(从几个keV到几十keV)。在聚焦的重联地点周围，有很大一部分(≳70%)向地面移动的粒子遇到了快速流动，并显著加速。我们的结果表明，快流电场在离子从近尾区到内磁层的加速过程中起主要作用，而不是其他常见的机制，如绝热Betatron过程和费米过程。此外，与磁重联相关的偶极阵面也会影响粒子加速。在全球尺度上，粒子可以先遇到重联区域，然后多次返回快流，因此加速是通过多次局部加速过程，导致粒子通过重联/尾部快速流获得能量∼50keV。全局模拟表明，粒子在注入环电流的过程中，加速过程涉及多个区域。
Particle injection by magnetotail reconnection plays an important role in the magnetospheric physics, since these particles may be accelerated to high energy and constituent energetic particles in the inner magnetosphere. In this paper, we trace such ion particles from a near‐Earth reconnection region to the inner magnetosphere self‐consistently in a 3‐D global hybrid simulation using ANGIE3D, and demonstrate the important roles of the earthward fast flows in the ion acceleration process in the tail plasma sheet. Although the particles can gain several times of their initial energy from the reconnection X‐line region, a dramatic increase of the ion energy (from a few keV up to a few tens of keV) occurs in a very short period of time due to their encounter with the earthward fast flows. A large portion (≳70%) of the earthward moving particles around the focused reconnection site encounter fast flows and are significantly accelerated. Our results indicate that fast flow electric fields play major roles, as opposed to other common mechanisms such as the adiabatic Betatron and Fermi processes, in ion acceleration from the near‐tail region to the inner magnetosphere. In addition, dipolarization fronts associated with magnetic reconnection also affect the particle acceleration. On the global scale, it is found that particles can encounter the reconnection region first and then return to the fast flows multiple times, and thus the acceleration is through multiple local acceleration processes, leading to particle energy ∼50 keV by reconnection/fast flows in the tail. The global simulation shows that particle acceleration involves multiple regions during their injection into the ring current.