Plasma Turbulence in the Interstellar Medium: Characteristics and Consequences

Steven Spangler博士（爱荷华大学）将探索星际介质中的湍流以及这种湍流在星际过程中所起的作用。研究计划的研究方法包括(1)利用甚大阵列（VLA）对通过HII区域观测的河外射电源进行新的射电天文观测，(2)利用甚大阵列和默奇森宽场阵列对附近脉冲星进行低无线电频率的新观测，以及(3)对附近星际云湍流的广泛光谱测量进行检查和重新分析。在拨款期内将进行的具体研究项目如下：(1)将使用VLA对6个HII区域及其相关气泡中约150个河外射电源样本进行法拉第旋转观测；(2)四颗脉冲星的低频（小于100兆赫）闪烁测量将透过“局部气泡”进行，这些脉冲星是弱散射的，闪烁数据将被检查是否存在“脉冲星弧”，其中包含了沿视线的距离和湍流分布的信息；(3)将分析现有的一组高质量的由附近星际云引起的吸收谱线的测量结果，以获取其中包含的有关这些云的湍流特性的信息；(4)轻电离分子云的湍流特性及其与分子离子的相互作用都将被研究。这项研究将通过对青年科学家在物理科学研究方法、射电天文和放射物理测量能力以及等离子体物理基础方面的个性化培训，使整个社会受益。Spangler博士对爱荷华大学本科生和研究生的指导将在该奖项下继续进行。这个研究项目还有一个外联部分，包括与爱荷华州的业余天文团体的联系，特别是爱荷华州锡达拉皮兹的锡达业余天文学家。

Dr. Steven Spangler (University of Iowa) will explore turbulence in the interstellar medium and the role such turbulence plays in interstellar processes. Methods of inquiry in the research program include (1) new radio-astronomical observations using the Very Large Array (VLA) of extragalactic radio sources viewed through HII regions, (2) new observations at low radio frequencies of nearby pulsars with the VLA and the Murchison Widefield Array, and (3) examination and re-analysis of extensive spectroscopic measurements of turbulence in nearby interstellar clouds. Specific research projects to be undertaken in the grant period are the following: (1) Faraday rotation observations will be made with the VLA of a sample of about 150 extragalactic radio sources viewed through 6 HII regions and their associated bubbles; (2) low frequency (less than 100 MHz) scintillation measurements will be made of four pulsars which are weakly scattered and viewed through the "Local Bubble": the scintillation data will be examined for the presence of "pulsar arcs", which contain information on the distance and distribution of turbulence along the line of sight; (3) an existing, high quality set of measurements of absorption lines due to nearby interstellar clouds will be analysed for the information it contains on the properties of turbulence in these clouds; (4) the properties of turbulence in the lightly ionized molecular clouds, and its interaction with molecular ions, will both be investigated.This research will benefit society as a whole through the individualized training of young scientists in the methods of physical science research, the capabilities of radioastronomical and radiophysical measurements, and in fundamentals of plasma physics. Dr. Spangler's mentorship of University of Iowa undergraduate and graduate students will continue under this award. This research program also has an outreach component, consisting of an association with amateur astronomy groups in Iowa, particularly the Cedar Amateur Astronomers in Cedar Rapids, Iowa.