太阳附近的一个致密等离子体球
A dense plasma globule in the solar neighborhood
摘要：
射电源J1819+3845在大约1999年至2007年之间经历了一段极端的星际闪烁。导致这种闪烁的等离子体结构被确定为距离太阳系仅为$1$ - $3\,$ pc，密度为$n_e\sim 10^2\,$ cm $^{-3}$，比周围星际密度高三个数量级（de Bruyn & Macquart 2015）。在这里，我们提出了无线电偏振图像的字段对J1819+3845在0.2，0.92和2 $\,$ m的波长。我们检测到一个椭圆形的等离子体球的近似大小$1^\circ \times \gtrsim 2^\circ$（长轴位置角的$\approx -40^\circ$），通过其法拉第旋转印记（$\approx 15\,$ rad $\,$ m $^{-2}$）的弥漫银河同步辐射。J1819+3845的极端闪烁最有可能是在球状体的湍流边界处引起的（J1819+3845目前被球状体遮蔽）。球状体的起源和确切性质仍然未知。我们的观察是第一次直接成像可能导致极端闪烁的等离子体结构。
英文摘要：
The radio source J1819+3845 underwent a period of extreme interstellar scintillation between circa 1999 and 2007. The plasma structure responsible for this scintillation was determined to be just $1$-$3\,$pc from the solar system and to posses a density of $n_e\sim 10^2\,$cm$^{-3}$ that is three orders of magnitude higher than the ambient interstellar density (de Bruyn & Macquart 2015). Here we present radio-polarimetric images of the field towards J1819+3845 at wavelengths of 0.2, 0.92 and 2$\,$m. We detect an elliptical plasma globule of approximate size $1^\circ \times \gtrsim 2^\circ$ (major-axis position angle of $\approx -40^\circ$), via its Faraday-rotation imprint ($\approx 15\,$rad$\,$m$^{-2}$) on the diffuse Galactic synchrotron emission. The extreme scintillation of J1819+3845 was most likely caused at the turbulent boundary of the globule (J1819+3845 is currently occulted by the globule). The origin and precise nature of the globule remain unknown. Our observations are the first time plasma structures that likely cause extreme scintillation have been directly imaged.
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