The Mechanism of Electron Injection and Acceleration in Transrelativistic Reconnection
The Mechanism of Electron Injection and Acceleration in Transrelativistic Reconnection
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DOI：
10.3847/1538-4357/ab3f2e
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发表时间：
2019-08
期刊：
影响因子：
--
通讯作者：
D. Ball;L. Sironi;F. Özel
中科院分区：
文献类型：
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作者：
D. Ball;L. Sironi;F. Özel
磁重联过程中的电子加速被认为在天体物理系统的时变高能发射中发挥着关键作用。通过跨相对论重联的细胞内粒子模拟，我们研究了低β电子质子等离子体中的电子注入和加速机制。我们通过改变引导场强度并选择是否触发重连接或让它自发演化来建立多种密度和场结构（例如，X点和等离子体）。我们表明，X 点和等离子体团的数量控制着电子加速的效率，X 点越多，效率越高。通过使用动态加速诊断，我们还表明与 X 点相关的非理想电场在电子加速的第一阶段发挥着关键作用。作为进一步的诊断，我们包括两组测试粒子，它们选择性地仅经历电场的某些组成部分。我们发现平行电场的面外分量决定了电子能量分布高能尾部的硬度。这些结果进一步加深了我们对这种磁重联状态下电子加速的理解，并对黑洞吸积流的现实模型具有影响。
Electron acceleration during magnetic reconnection is thought to play a key role in time-variable high-energy emission from astrophysical systems. By means of particle-in-cell simulations of transrelativistic reconnection, we investigate electron injection and acceleration mechanisms in low-β electron–proton plasmas. We set up a diversity of density and field structures (e.g., X-points and plasmoids) by varying the guide field strength and choosing whether to trigger reconnection or let it spontaneously evolve. We show that the number of X-points and plasmoids controls the efficiency of electron acceleration, with more X-points leading to a higher efficiency. Using on-the-fly acceleration diagnostics, we also show that the nonideal electric fields associated with X-points play a critical role in the first stages of electron acceleration. As a further diagnostic, we include two populations of test particles that selectively experience only certain components of electric fields. We find that the out-of-plane component of the parallel electric field determines the hardness of the high-energy tail of the electron energy distribution. These results further our understanding of electron acceleration in this regime of magnetic reconnection and have implications for realistic models of black hole accretion flows.