等离子体湍流中电子剪切流不稳定性产生亚亚尺度磁空穴

IF 4.8 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS
Giuseppe Arrò, Francesco Pucci, Francesco Califano, Maria Elena Innocenti, Giovanni Lapenta
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引用次数: 0

摘要

磁孔是磁化等离子体中与强磁场凹陷相关的相干结构。它们在许多天体物理环境中被广泛地观测到,但它们的起源仍在争论中。在这项工作中,我们研究了亚亚尺度MHs的形成,使用了一个完全动力学的等离子体湍流二维模拟,初始化参数为典型的地球磁鞘。我们的分析表明,湍流能够从大尺度波动中产生亚尺度的高质量,其机制如下:首先,非线性大尺度动力学自发地导致了薄而细长的电子速度剪切的发展;然后这些结构变得不稳定到电子开尔文-亥姆霍兹不稳定,并分裂成小尺度的电子漩涡;这些涡旋所携带的电流在局部减弱磁场,诱发亚尺度磁磁体的形成。由此产生的高质量卫星显示出与卫星观测和以前的数值研究相一致的特征。我们最后讨论了观测到的亚尺度高质量粒子的动力学性质,表明它们具有复杂的非麦克斯韦电子速度分布,具有各向异性和涡旋性特征。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Generation of Subion Scale Magnetic Holes from Electron Shear Flow Instabilities in Plasma Turbulence
Abstract Magnetic holes (MHs) are coherent structures associated with strong magnetic field depressions in magnetized plasmas. They are observed in many astrophysical environments at a wide range of scales, but their origin is still under debate. In this work, we investigate the formation of subion scale MHs using a fully kinetic 2D simulation of plasma turbulence initialized with parameters typical of the Earth’s magnetosheath. Our analysis shows that the turbulence is capable of generating subion scale MHs from large scale fluctuations via the following mechanism: first, the nonlinear large scale dynamics spontaneously leads to the development of thin and elongated electron velocity shears; these structures then become unstable to the electron Kelvin–Helmholtz instability and break up into small scale electron vortices; the electric current carried by these vortices locally reduces the magnetic field, inducing the formation of subion scale MHs. The MHs thus produced exhibit features consistent with satellite observations and with previous numerical studies. We finally discuss the kinetic properties of the observed subion scale MHs, showing that they are characterized by complex non-Maxwellian electron velocity distributions exhibiting anisotropic and agyrotropic features.
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来源期刊
Astrophysical Journal
Astrophysical Journal 地学天文-天文与天体物理
CiteScore
8.40
自引率
30.60%
发文量
2854
审稿时长
1 months
期刊介绍: The Astrophysical Journal is the foremost research journal in the world devoted to recent developments, discoveries, and theories in astronomy and astrophysics.
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