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arXiv 1208.0849astro-ph.HEphysics.plasm-ph
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三维相对论磁重联中的磁通绳网络和粒子加速

A Flux Rope Network and Particle Acceleration in Three Dimensional Relativistic Magnetic Reconnection

Daniel Kagan, Milos Milosavljevic, Anatoly Spitkovsky

摘要:

利用三维粒子模拟方法研究了相对论对等离子体中的导场磁重联和粒子加速问题。撕裂不稳定性是主导模式在所有的引导场强度的电流片,而线性扭结模式是次要的,即使没有引导场。倾斜模式似乎被完全抑制。在其非线性演化过程中,重联层形成了一个相互连接和相互作用的磁通量绳网络。随着较小的磁通绳合并成较大的磁通绳,重联层朝着三维的无序状态发展,在这种状态下,产生的磁通绳段包含等离子体趋肤深度尺度上的磁性子结构。嵌入在通量绳,我们检测空间和时间上的间歇性网站的耗散反映在平行电场的峰值。磁耗散和粒子加速持续到模拟结束,具有较高磁化和较低引导场强度的模拟表现出更大和更快的能量转换和粒子加速。在我们最大的模拟结束时,粒子能谱达到一个延伸到高洛伦兹因子的尾部,这是最好的模拟与两个额外的热组件的组合。我们确认,主要的超导机制是加速的电场在X线区域。我们讨论了宏观重联网站,我们的结果的影响,我们的结果可能会被期望在系统中具有较高的磁化。

英文摘要:

We investigate guide-field magnetic reconnection and particle acceleration in relativistic pair plasmas with three-dimensional particle-in-cell (PIC) simulations of a kinetic-scale current sheet in a periodic geometry at low magnetizations. The tearing instability is the dominant mode in the current sheet for all guide field strengths, while the linear kink mode is less important even without guide field. Oblique modes seem to be suppressed entirely. In its nonlinear evolution, the reconnection layer develops a network of interconnected and interacting magnetic flux ropes. As smaller flux ropes merge into larger ones, the reconnection layer evolves toward a three-dimensional, disordered state in which the resulting flux rope segments contain magnetic substructure on plasma skin depth scales. Embedded in the flux ropes, we detect spatially and temporally intermittent sites of dissipation reflected in peaks in the parallel electric field. Magnetic dissipation and particle acceleration persist until the end of the simulations, with simulations with higher magnetization and lower guide field strength exhibiting greater and faster energy conversion and particle energization. At the end of our largest simulation, the particle energy spectrum attains a tail extending to high Lorentz factors that is best modeled with a combination of two additional thermal components. We confirm that the primary energization mechanism is acceleration by the electric field in the X-line region. We discuss the implications of our results for macroscopic reconnection sites, and which of our results may be expected to hold in systems with higher magnetizations.

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