Kinetic simulations of imbalanced turbulence in a relativistic plasma: Net flow and particle acceleration
Kinetic simulations of imbalanced turbulence in a relativistic plasma: Net flow and particle acceleration
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相对论等离子体中不平衡湍流的动力学模拟：净流和粒子加速
DOI：
10.1093/mnras/stab3209
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发表时间：
2021
影响因子：
4.8
通讯作者：
Begelman, Mitchell C
中科院分区：
文献类型：
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作者：
Hankla, Amelia M;Zhdankin, Vladimir;Werner, Gregory R;Uzdensky, Dmitri A;Begelman, Mitchell C
湍流高能天体物理系统通常具有不对称能量注入的特征：例如，阿尔文波从吸积盘传播到其日冕。这样的系统是“不平衡的”：与大尺度磁场平行和反平行的能量通量不相等。过去，不平衡湍流的数值研究主要集中在磁流体动力学领域。在这项研究中，我们使用 3D 粒子在细胞 (PIC) 模拟来研究无碰撞、超相对论热、磁化对等离子体中外部驱动的不平衡湍流。我们发现注入的电磁动量有效地转化为等离子体动量，从而导致沿着背景磁场的净运动，速度高达光速的很大一部分。这一发现对于吸积盘风的发射具有重要意义。我们还发现，尽管不平衡湍流中粒子加速的时间尺度比平衡湍流中的要慢，但它最终会产生类似于平衡湍流的幂律能量分布。我们的结果对黑洞吸积盘日冕、风和喷流有影响。
Turbulent high-energy astrophysical systems often feature asymmetric energy injection: for instance, Alfvén waves propagating from an accretion disc into its corona. Such systems are ‘imbalanced’: the energy fluxes parallel and antiparallel to the large-scale magnetic field are unequal. In the past, numerical studies of imbalanced turbulence have focused on the magnetohydrodynamic regime. In this study, we investigate externally driven imbalanced turbulence in a collision-less, ultrarelativistically hot, magnetized pair plasma using 3D particle-in-cell (PIC) simulations. We find that the injected electromagnetic momentum efficiently converts into plasma momentum, resulting in net motion along the background magnetic field with speeds up to a significant fraction of lightspeed. This discovery has important implications for the launching of accretion disc winds. We also find that although particle acceleration in imbalanced turbulence operates on a slower time-scale than in balanced turbulence, it ultimately produces a power-law energy distribution similar to balanced turbulence. Our results have ramifications for black hole accretion disc coronae, winds, and jets.