用最长的空-地干涉仪基线研究近区湍流星际等离子体的RadioAstron
RadioAstron Studies of the Nearby, Turbulent Interstellar Plasma With the Longest Space-Ground Interferometer Baseline
摘要：
10米空间射电望远镜与阿雷西博300米望远镜和韦斯特博克综合射电望远镜以324兆赫的频率联合对脉冲星B 0950 +08进行了射电天文学空间-地面VLBI观测，对观测结果进行了分析，以研究这颗附近脉冲星方向上的等离子体不均匀性。观测是在330，000公里的航天器距离上进行的，因此预测基线为220，000公里，提供了在米波长上所达到的最高角分辨率。我们的分析是基于结构和相干函数的基本行为。我们发现脉冲星在两个频率尺度上都表现出闪烁，都远小于观测频率，但调制小于100%。我们推断，散射是弱的，但折射楔分散的闪烁图案。这个“宇宙棱镜”的折射角被测量为θ_0 =1.1 - 4.4质量，折射方向近似垂直于观察者的速度。我们发现，所观察到的闪烁效应的参数表明，两个等离子体层位于沿视线的脉冲星，在4.4 - 16.4秒差距和26 - 170秒差距的距离，并在不同的方向相对于视线。两层的湍流谱发现遵循指数为gamma_1 = gamma_2 = 3.00 +/- 0.08的幂律，显著不同于湍流的Kolmogorov谱的预期指数，gamma=11/3。
英文摘要：
RadioAstron space-ground VLBI observations of the pulsar B0950+08, conducted with the 10-m space radio telescope in conjunction with the Arecibo 300-m telescope and Westerbork Synthesis Radio Telescope at a frequency of 324 MHz, were analyzed in order to investigate plasma inhomogeneities in the direction of this nearby pulsar. The observations were conducted at a spacecraft distance of 330,000 km, resulting in a projected baseline of 220,000 km, providing the greatest angular resolution ever achieved at meter wavelengths. Our analysis is based on fundamental behavior of structure and coherence functions. We find that the pulsar shows scintillation on two frequency scales, both much less than the observing frequency; but modulation is less than 100%. We infer that the scattering is weak, but a refracting wedge disperses the scintillation pattern. The refraction angle of this "cosmic prism" is measured as theta_0=1.1 - 4.4 mas, with the refraction direction being approximately perpendicular to the observer velocity. We show that the observed parameters of scintillation effects indicate that two plasma layers lie along the line of sight to the pulsar, at distances of 4.4 - 16.4 pc and 26 - 170 pc, and traveling in different directions relative to the line of sight. Spectra of turbulence for the two layers are found to follow a power law with the indices gamma_1 = gamma_2 = 3.00 +/- 0.08, significantly different from the index expected for a Kolmogorov spectrum of turbulence, gamma=11/3.
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