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arXiv 2408.09609astro-ph.HE
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脉冲星射电辐射中偏振模式跃迁时的位置角和椭率角行为

Behavior of the Position and Ellipticity Angles at Polarization Mode Transitions in Pulsar Radio Emission

M. M. McKinnon

AI总结:

本研究针对射电脉冲星偏振模式跃迁时位置角与椭率角的变化行为,检验四种偏振模型,发现跃迁轨迹均遵循庞加莱球测地线,且模型解释不唯一,偏振度与椭率角偏移受模式强度涨落统计特性调控。

摘要:

射电脉冲星的偏振观测表明,偏振矢量位置角的突变可能伴随矢量椭率角的大幅偏移,这表明该矢量会经过庞加莱球的右圆极点或左圆极点附近。这种角度行为可以通过正交偏振模式的主导权跃迁,或是模式间相位差变化引发的矢量旋转来解释。\n为量化并理解模式跃迁时的角度行为,研究检验了四种偏振模型:相干偏振模式、部分相干模式、带非正交偏振矢量的非相干模式,以及带有椭圆偏振辐射分量的非相干正交模式。在所有四种模型中,模式跃迁在庞加莱球上的轨迹都遵循连接各模式偏振矢量取向的测地线。\n这些模型的结果可能相似,这表明在特定模型框架下对观测到的跃迁的解释不一定唯一。辐射的偏振度和平均椭率角取决于模式强度涨落的统计特性:偏振度随涨落增强而升高;当模式强度准稳定时,椭率角的偏移幅度可能很大,而当强度涨落较大时,这种偏移会受到抑制。

英文摘要:

Polarization observations of radio pulsars show that abrupt transitions in the polarization vector's position angle can be accompanied by large excursions in the vector's ellipticity angle, suggesting the vector passes near the right or left circular pole of the Poincaré sphere. The behavior of the angles can be explained by a transition in dominance of the orthogonal polarization modes or a vector rotation caused by a change in the phase difference between the modes. Four polarization models are examined to quantify and understand the behavior of the angles at a mode transition: coherent polarization modes, partially coherent modes, incoherent modes with nonorthogonal polarization vectors, and incoherent orthogonal modes with an elliptically polarized emission component. In all four models, the trajectory of the mode transition on the Poincaré sphere follows the geodesic that connects the orientations of the mode polarization vectors. The results from the models can be similar, indicating that the interpretation of an observed transition within the context of a particular model is not necessarily unique. The polarization fraction of the emission and the average ellipticity angle depend upon the statistical character of the mode intensity fluctuations. The polarization fraction increases as the fluctuations increase. The excursion in ellipticity angle can be large when the mode intensities are quasi-stable and is suppressed when the intensity fluctuations are large.

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