论文标题

无线电脉冲剖面中曲率辐射散射的证据

Evidence for scattering of curvature radiation in radio pulsar profiles

论文作者

Dyks, J.

论文摘要

无线电脉冲星表现出几种无法解释的现象,尤其是具有明显的核心结构和有趣的频率演化的平均脉冲曲线。我表明可以通过反康普顿散射的基本几何特性来解释它们。如果散射发生在偶极磁层中并且平均无路径长,则预期嵌套锥结构的圆锥大小比为三分之二,这与观测值一致。作为一个不连续的过程,散射与从畸变 - 压抑效应得出的发射环的离散高度结构一致。假设向向散射的信号是曲率辐射(CR),则可以将观察到的分叉成分(BC)解释为CR的放大微光:BCS是宽的低频CR微束,这些微束在频率上以宽度散射在散射磁场中散射而宽度降低,并且频率已在频率上进行了缩小。 BCS的较大通量部分是由将完整发射光谱压缩到狭窄的观测带宽中引起的,这解释了频率分辨的BCS为何具有频率集成的形状。宽的低频微束可以包含大型磁层量,从而大大减少了相干性所需的能量要求。因此,BC的特性表明,观察到的调制通量受散射驱动的蓝光和光谱压缩的强烈影响。相对论的光束公式(1/γ)并不总是适用,因为它可能不会直接应用于某些蓝光轮廓特征。

Radio pulsars exhibit several unexplained phenomena, in particular the average pulse profiles with the apparent core-cone structure and interesting frequency evolution. I show that they can be interpreted through essential geometric properties of the inverse Compton scattering. If the scattering occurs in a dipolar magnetosphere and the mean-free-path is long, a nested cone structure is expected with the cone size ratio of two-thirds, which is consistent with observations. Being a discontinuous process, the scattering is consistent with the discrete altitude structure of emission rings as derived from aberration-retardation effects. Assuming that the upscattered signal is the curvature radiation (CR), one can interpret the observed bifurcated components (BCs) as a magnified microbeam of CR: the BCs are wide low-frequency CR microbeams that have been upshifted in frequency with their width preserved by beam-copying scattering in divergent magnetic field. The large flux of BCs is partly caused by compression of the full emitted spectrum into the narrow observed bandwidth, which explains why the frequency-resolved BCs have the frequency-integrated shape. The wide low-frequency microbeams can encompass large magnetospheric volumes, which considerably abates the requirements of the energy needed for coherency. The properties of BCs thus suggest that the observed modulated radio flux is strongly affected by the scattering-driven blueshift and spectral compression. The relativistic beaming formula (1/γ) is not always applicable, in the sense that it may not be directly applied to some blueshifted profile features.

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