Parkes observations for project P934 semester 2016OCTS_BPSR_02

On the smallest scales, the warm interstellar medium contains surprisingly complex structure, including extremely overdense filaments and blobs of plasma that remain intact for months, despite physical processes that should cause them to disperse on short (week) time scales. It is possible that magnetization plays a role in confining this plasma. On these AU length scales the plasma is best probed by observing the scintillations of compact background radio sources such as pulsars and quasars. Recent observations show that overdensities are confined to narrow regions along lines of sight. Over the last decade, improvements in the analysis of scintillation have enabled better characterization of these structures. These studies however have focused on the ISM in the solar-system neighbourhood and the Galactic plane. Here we propose to observe pulsars at high galactic latitudes to extend the sample lines of sight. We will determine if the scattering regions are confined to the Galactic plane or persist into the halo of the galaxy. We will also search for (or place limits on) magnetic field variations within these scattering regions and discrete structures. Our observations will also provide important constraints on the scintillation of fast radio bursts, extragalactic sources which may be magnified by the similar structures to those studied here.

在最小尺度下，暖星际介质（warm interstellar medium）中存在着出人意料的复杂结构，包含密度极高的等离子体丝状体与团块——尽管存在应使其在短至周级时间尺度内弥散的物理过程，这些结构却能保持完整达数月之久。磁化作用可能在约束这类等离子体的过程中发挥了作用。在天文单位（Astronomical Unit, AU）尺度下，探测这类等离子体的最佳方式是观测致密背景射电源的射电闪烁（scintillation）现象，这类射电源包括脉冲星（pulsar）与类星体（quasar）。近期观测结果表明，这类高密度结构仅局限于视线方向上的狭窄区域内。过去十余年间，射电闪烁分析技术的进步使得我们能够对这类结构实现更精准的特性表征。不过此前的相关研究均聚焦于太阳系邻近区域与银河平面（Galactic plane）内的星际介质（Interstellar Medium, ISM）。本研究计划通过观测高银纬脉冲星，以拓展视线方向的样本覆盖范围。我们将以此判定：这类散射区域是仅局限于银河平面，还是能够延伸至星系晕（Galactic halo）之中。此外，我们还将搜寻这类散射区域与离散结构内的磁场变化，或对其设置约束上限。本研究的观测结果还将为快速射电暴（Fast Radio Burst, FRB）的射电闪烁现象提供重要约束——这类河外射电源的辐射可能会被与本研究中所分析的同类结构所放大。