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arXiv 2006.15243astro-ph.HEhep-ph
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脉冲星射电发射机制:一个评论

Pulsar radio emission mechanisms: a critique

D. B. Melrose, M. Z. Rafat, A. Mastrano

摘要:

我们严格考虑了三种最受欢迎的脉冲星射电发射机制:相干曲率发射(CCE),光束驱动的相对论等离子体发射(RPE)和反常多普勒发射(ADE)。我们假设脉冲星等离子体是一维的,以体洛伦兹因子$γ_{\rm s} \gg \langle γ\rangle -1 \gtrsim 1$向外流动,其中$\langle γ\rangle $是等离子体在静止坐标系中的本征扩散。我们认为,在多云模型中形成的光束是无效的,在本质上相对论的情况下,合理的参数,因为超车需要太长的时间。我们认为,在静止帧的粒子分布的默认选择是一个J{ü}ttner分布和相对论流应包括通过应用洛伦兹变换的静止帧分布,而不是广泛假设的相对论流高斯分布。我们发现,束流驱动波的增长受到以下因素的严重限制:(a)脉冲星等离子体中的波动特性,(b)束流与背景之间的分离条件,以及(c)脉冲星坐标系中等离子体的不均匀性。动力学不稳定性的增长率是小得多,增长波的带宽是大得多的J{ü}ttner分布比相对论流高斯分布。对于J{ü}ttner分布,根本没有反应不稳定性发生。我们的结论是,没有CCE,RPE和ADE是站得住脚的一般脉冲星射电发射机制的“可接受的”假设的脉冲星等离子体。

英文摘要:

We consider critically the three most widely favored pulsar radio emission mechanisms: coherent curvature emission (CCE), beam-driven relativistic plasma emission (RPE) and anomalous Doppler emission (ADE). We assume that the pulsar plasma is one dimensional (1D), streaming outward with a bulk Lorentz factor $γ_{\rm s} \gg \langle γ\rangle -1 \gtrsim 1$, where $\langle γ\rangle $ is the intrinsic spread in the rest frame of the plasma. We argue that the formation of beams in a multi-cloud model is ineffective in the intrinsically relativistic case for plausible parameters, because the overtaking takes too long. We argue that the default choice for the particle distribution in the rest frame is a J{ü}ttner distribution and that relativistic streaming should be included by applying a Lorentz transformation to the rest-frame distribution, rather than the widely assumed relativistically streaming Gaussian distribution. We find that beam-driven wave growth is severely restricted by (a) the wave properties in pulsar plasma, (b) a separation condition between beam and background, and (c) the inhomogeneity of the plasma in the pulsar frame. The growth rate for the kinetic instability is much smaller and the bandwidth of the growing waves is much larger for a J{ü}ttner distribution than for a relativistically streaming Gaussian distribution. No reactive instability occurs at all for a J{ü}ttner distribution. We conclude that none of CCE, RPE and ADE in tenable as the generic pulsar radio emission mechanism for ``plausible'' assumptions about the pulsar plasma.

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