Parkes observations for project P934 semester 2016OCTS_BPSR_04

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，温暖的星际介质(interstellar medium, ISM)中存在着出人意料的复杂结构，包括密度极高的丝状结构与等离子体团块——尽管存在应使其在短短数周内消散的物理过程，这类结构却能保持完整达数月之久。磁化效应有可能在约束此类等离子体的过程中发挥作用。
在以天文单位(Astronomical Unit, AU)为量度的尺度上，观测致密背景射电源（如脉冲星与类星体）的闪烁现象，是探测该区域等离子体的最优手段。近期的观测结果表明，高密度区域仅局限于视线方向上的狭窄区间内。
过去十年间，闪烁现象分析技术的进步使得我们能够对这类结构开展更为精细的表征研究。但此前的相关研究均仅聚焦于太阳系邻近区域与银道面内的星际介质。本次研究计划对高银纬脉冲星开展观测，以拓展视线方向的样本覆盖范围。我们将探明散射区域是仅局限于银道面，还是同样延伸至星系银晕之中。此外，我们还将在这些散射区域与离散结构中搜寻磁场变化，或给出其约束上限。
本次观测还将为快速射电暴(fast radio bursts, FRB)的闪烁现象研究提供重要约束——这类河外天体有可能会被与本研究中所分析的同类结构所放大。