Explosive X-point collapse in relativistic magnetically dominated plasma
Explosive X-point collapse in relativistic magnetically dominated plasma
复制标题
相对论性磁控等离子体中的爆炸性 X 点塌缩
DOI：
10.1017/s0022377817000629
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发表时间：
2017
影响因子：
2.5
通讯作者：
O. Porth
中科院分区：
文献类型：
--
作者：
M. Lyutikov;L. Sironi;S. Komissarov;O. Porth
蟹状星云中伽马射线耀斑的极端特性对我们关于相对论天体物理等离子体中粒子加速性质的想法提出了明显的挑战。随机类型的标准机制似乎不太可能在这里起作用，因此理论学家的注意力已转向磁重联事件中的线性加速。在这一系列论文中，我们试图发展一种高磁化相对论等离子体中爆炸性磁重联理论，该理论可以解释蟹状耀斑的极端参数。在第一篇论文中，我们重点关注 X 点塌陷的性质。使用分析和数值方法（流体和细胞内粒子模拟），我们将 Syrovatsky 的这种塌陷的经典模型扩展到相对论状态。我们发现，坍缩可以导致宏观尺度上的重联率接近光速。在塌缩过程中，等离子体粒子被缺乏电荷的电场加速，该电场可以达到（甚至超过）局部磁场的值。重联的爆炸阶段产生非热幂律尾部，其斜率取决于平均磁化强度 $\unicode[STIX]{x1D70E}$ 。对于足够高的磁化强度和消失的引导场，非热粒子谱由两个组成部分组成：具有软谱的低能粒子群，在数量普查中占主导地位；以及具有硬光谱的高能粒子群，具有解释蟹状耀斑所需的所有特性。
The extreme properties of the gamma-ray flares in the Crab nebula present a clear challenge to our ideas on the nature of particle acceleration in relativistic astrophysical plasma. It seems highly unlikely that standard mechanisms of stochastic type are at work here and hence the attention of theorists has switched to linear acceleration in magnetic reconnection events. In this series of papers, we attempt to develop a theory of explosive magnetic reconnection in highly magnetized relativistic plasma which can explain the extreme parameters of the Crab flares. In the first paper, we focus on the properties of the X-point collapse. Using analytical and numerical methods (fluid and particle-in-cell simulations) we extend Syrovatsky’s classical model of such collapse to the relativistic regime. We find that the collapse can lead to the reconnection rate approaching the speed of light on macroscopic scales. During the collapse, the plasma particles are accelerated by charge-starved electric fields, which can reach (and even exceed) values of the local magnetic field. The explosive stage of reconnection produces non-thermal power-law tails with slopes that depend on the average magnetization $\unicode[STIX]{x1D70E}$ . For sufficiently high magnetizations and vanishing guide field, the non-thermal particle spectrum consists of two components: a low-energy population with soft spectrum that dominates the number census; and a high-energy population with hard spectrum that possesses all the properties needed to explain the Crab flares.