Solitary Magnetic Structures at Quasi-Parallel Collisionless Shocks: Formation
Solitary Magnetic Structures at Quasi-Parallel Collisionless Shocks: Formation
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DOI：
10.1029/2020gl090800
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发表时间：
2021-01-16
影响因子：
5.2
通讯作者：
Burch, James
中科院分区：
文献类型：
--
作者：
Chen, Li-Jen;Wang, Shan;Burch, James
孤立磁结构被称为SLAMS（短大振幅磁结构）被认为是准平行几何无碰撞激波的基本元素。然而，它们形成的物理基础仍然是一个悬而未决的问题。在本文中，我们使用磁层多尺度使命的测量结合完全动力学模拟研究SLAMS的形成。我们发现太阳风离子与右旋圆极化电磁波之间的回旋共振导致磁场放大。由不断增长的磁场引起的回旋捕获增加了等离子体密度，从而进一步增强了电流和场。SLAMS的孤立性质源于一个类似拍频的磁场包络，其中最大值设置了非线性增长的初始位置。我们的研究结果提出了一个概念上的SLAMS的进步，并可能揭示新的光在天体物理冲击磁场放大的开放性问题。
Solitary magnetic structures known as SLAMS (short large-amplitude magnetic structures) have been considered as essential elements of collisionless shocks with quasi-parallel geometries. Yet the physics underlying their formation remains an open question. In this paper, we use measurements from the magnetospheric multiscale mission combined with fully kinetic simulations to study the formation of SLAMS. We find that gyro-resonance between solar wind ions and right-hand circularly polarized electromagnetic waves results in magnetic field amplification. Gyro-trapping by the growing magnetic field buildup the plasma density that further enhances the current and field. The solitary nature of SLAMS stems from a beat-like magnetic field envelope where the maximum sets the initial location for nonlinear growth. Our results present a conceptual advance on SLAMS, and may shed new light on the open question of magnetic field amplification at astrophysical shocks.