Bunch Expansion as a Cause for Pulsar Radio Emissions
Bunch Expansion as a Cause for Pulsar Radio Emissions
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束膨胀是脉冲星无线电发射的原因
DOI：
10.3847/1538-4357/ac2c64
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
J. Büchner
中科院分区：
文献类型：
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作者：
J. Benáček;P. Muñoz;J. Büchner
脉冲星磁层中的级联过程产生的电子-正电子云（聚束）产生的电磁波被用来解释脉冲星的射电辐射。为了验证这一假设，我们第一次利用粒子在细胞（PIC）代码模拟研究依赖于电子和正电子的初始相对漂移速度，等离子体温度和束之间的距离的电子-正电子束的非线性演化。为此，我们利用PIC代码ACRONYM与高阶场求解器和粒子加权因子，适当地描述相对论对等离子体。我们发现，束团膨胀主要取决于电子-正电子的相对漂移速度。有限的漂移速度被发现会导致在束团密度梯度达到E <$7.5 × 105 V cm−1（E/（m e c ω p e −1）<$4.4）和强等离子体加热时产生强静电超光速波。其结果是，高达15%的初始动能转化为电场能。假设相同的电子和正电子分布，我们发现，最快的（在束参考系）粒子的连续发射束最终在动量（速度）空间重叠。这种重叠导致双流不稳定性，产生电场振幅高达E <$1.9 × 104 V cm−1（E/（m e c ω p e −1）<$0.11）的静电亚光速波。我们发现，在所有的模拟中，电子-正电子聚束的演化可能会导致静电超光速或亚光速波的产生，原则上，这可能是在无线电波范围内观察到的电磁辐射的背后。
Electromagnetic waves due to electron–positron clouds (bunches), created by cascading processes in pulsar magnetospheres, have been proposed to explain the pulsar radio emission. In order to verify this hypothesis, we utilized for the first time Particle-in-Cell (PIC) code simulations to study the nonlinear evolution of electron–positron bunches dependant on the initial relative drift speeds of electrons and positrons, plasma temperature, and distance between the bunches. For this sake, we utilized the PIC code ACRONYM with a high-order field solver and particle weighting factor, appropriate to describe relativistic pair plasmas. We found that the bunch expansion is mainly determined by the relative electron–positron drift speed. Finite drift speeds were found to cause the generation of strong electrostatic superluminal waves at the bunch density gradients that reach up to E ∼ 7.5 × 105 V cm−1 (E/(m e c ω p e −1) ∼ 4.4) and strong plasma heating. As a result, up to 15% of the initial kinetic energy is transformed into the electric field energy. Assuming the same electron and positron distributions, we found that the fastest (in the bunch reference frame) particles of consecutively emitted bunches eventually overlap in momentum (velocity) space. This overlap causes two-stream instabilities that generate electrostatic subluminal waves with electric field amplitudes reaching up to E ∼ 1.9 × 104 V cm−1 (E/(m e c ω p e −1) ∼ 0.11). We found that in all simulations the evolution of electron–positron bunches may lead to the generation of electrostatic superluminal or subluminal waves, which, in principle, can be behind the observed electromagnetic emissions of pulsars in the radio wave range.
多选通场发射器的研制
DOI：
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发表时间：
2013
期刊：
影响因子：
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作者：
H.Mimura;Y.Neo;T.Aoki;T.Yoshida and M.Nagao
通讯作者：
T.Yoshida and M.Nagao