We show that the Weibel or current filamentation instability can lead to the emission of circularly polarized radiation. Using particle-in-cell simulations and a radiation post-processing numerical algorithm, we demonstrate that the level of circular polarization increases with the initial plasma magnetization, saturating at ${\sim }13\,\%$ when the magnetization, given by the ratio of magnetic energy density to the electron kinetic energy density, is larger than 0.05. Furthermore, we show that this effect requires an ion–electron mass ratio greater than unity. These findings, which could also be tested in currently available laboratory conditions, show that the recent observation of circular polarization in gamma-ray burst afterglows could be attributed to the presence of magnetized current filaments driven by the Weibel or current filamentation instability.

中文翻译：

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磁化电流灯丝作为圆偏振光源

我们表明 Weibel 或电流丝状不稳定性会导致圆偏振辐射的发射。使用细胞内粒子模拟和辐射后处理数值算法，我们证明圆极化水平随着初始等离子体磁化强度的增加而增加，饱和度为 ${\sim }13\,\%$ 当由磁能密度与电子动能密度之比给出的磁化强度大于 0.05 时。此外，我们表明这种效应需要离子 - 电子质量比大于 1。这些发现也可以在目前可用的实验室条件下进行测试，表明最近在伽马射线爆发余辉中观察到的圆极化可归因于由 Weibel 驱动的磁化电流细丝或电流细丝化不稳定性的存在。