GRB冲击中的正负电子对加载和上游磁场的起源
Electron-Positron Pair Loading and the Origin of the Upstream Magnetic Field in GRB Shocks
摘要：
在这里，我们调查的影响等离子体不稳定性驱动的快速电子/正电子对级联，这是由于原始光谱的种子分数的背散射的结果出现在GRB源的环境中。电子/正电子对的注入在周围介质中引起强烈的流运动。因此，我们可以预期，在前向激波之前的电子对富集介质在与辐射锋厚度相当的长度尺度上会受到强烈的剪切。使用三维粒子模拟，我们表明，这些流动的电子/正电子对驱动的等离子体不稳定性负责近均分，湍流磁场的激发。我们的研究结果揭示了在确保电子/正电子对和离子之间的有效耦合的电磁双折射不稳定性的重要性，并可能有助于解释在伽玛暴冲击的大上游领域的起源。
英文摘要：
We investigate here the effects of plasma instabilities driven by rapid electron/positron pair cascades, which arise in the environment of GRB sources as a result of back-scattering of a seed fraction of the original spectrum. The injection of electron/positron pairs induces strong streaming motions in the ambient medium. One therefore expects the pair-enriched medium ahead of the forward shock to be strongly sheared on length scales comparable to the radiation front thickness. Using three-dimensional particle-in-cell simulations, we show that plasma instabilities driven by these streaming electron/positron pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between electron/positron pairs and ions, and may help explain the origin of large upstream fields in GRB shocks.
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