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arXiv 2006.01788astro-ph.HE
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研究脉冲星亚脉冲漂移的内加速区火花运动机制

A Mechanism of Spark Motion in Inner Acceleration Region to Investigate Subpulse Drifting in Pulsars

Rahul Basu, Dipanjan Mitra, George I. Melikidze

摘要:

相干射电辐射是由恒星表面附近的内加速区(IAR)中的火花放电产生的相对论流动的非稳态等离子体流中的不稳定性激发的。大量的详细工作表明,IAR是由非偶极磁场主导的部分屏蔽间隙(PSG),离子从表面连续流出。亚脉冲漂移现象的起源是由于PSG中火花的可变$\mathbf{E}\times\mathbf{B}$漂移,其中火花滞后于脉冲星的共转速度。详细的观察显示了各种各样的子脉冲漂移行为,其中在不同分量的配置文件中的子脉冲有不同的相位轨迹。但是,漂移周期性被认为是恒定的,在测量误差范围内,跨越轮廓的所有分量。利用PSG中火花滞后于共转速度的概念以及表面非偶极磁场的不同取向,我们模拟了在具有代表性的样品中的预期单脉冲行为。我们的研究结果表明,不同类型的漂移相位行为可以使用这些简单的假设,在一个非偶极IAR的火花动力学再现。

英文摘要:

Coherent radio emission in pulsars is excited due to instabilities in a relativistically streaming non-stationary plasma flow, which is generated from sparking discharges in the inner acceleration region (IAR) near the stellar surface. A number of detailed works have shown the IAR to be a partially screened gap (PSG) dominated by non-dipolar magnetic fields with continuous outflow of ions from the surface. The phenomenon of subpulse drifting is expected to originate due to variable $\mathbf{E}\times\mathbf{B}$ drift of the sparks in PSG, where the sparks lag behind corotation velocity of the pulsar. Detailed observations show a wide variety of subpulse drifting behaviour where subpulses in different components of the profile have different phase trajectories. But the drifting periodicity is seen to be constant, within measurement errors, across all components of the profile. Using the concept of sparks lagging behind corotation speed in PSG as well as the different orientations of the surface non-dipolar magnetic fields we have simulated the expected single pulse behaviour in a representative sample of pulsars. Our results show that the different types of drifting phase behaviour can be reproduced using these simple assumptions of spark dynamics in a non-dipolar IAR.

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