RUI: Pulsar Scintillation and the Interstellar Medium

AST0098561恒星脉冲星的闪烁或强度变化可以用来探测大小与太阳系相似的星际介质。由于闪烁是由星际气体电离成分的微小密度变化引起的，对脉冲星闪烁的详细研究可以获得关于星际气体是如何聚集的信息，它是否表现出湍流，以及密度变化是如何启动和维持的。这些问题对于理解我们银河系的动力学以及其他类似我们的螺旋星系的动力学至关重要。动态频谱是射电频谱的连续集合，通常以一分钟的间隔获得几个小时的射电频谱。有时，由于星际介质中的多路径散射，动态光谱显示出组织松散的交叉图案，以及更典型的随机图案。最近的研究表明，当进行调和分析时，这种交错模式在变换空间中具有明显且轮廓清晰的特征。奥伯林学院的丹尼尔·斯泰内布赖恩博士将利用阿雷西博射电望远镜和西弗吉尼亚州绿岸新的全定向射电望远镜的高灵敏度观测来探索这一现象。通过观察谐波信号在频率和时间上是如何弯曲的，可以确定散射材料的位置。从观测的这一细节和其他细节中，可以找到散射体的物理尺寸。这将有助于理解散射物质的物理性质，并将其与其他天体物理现象联系起来，例如超新星遗迹或非常年轻或非常古老的恒星的湍流流出。确定这一现象的发生频率及其随无线电频率的变化将使我们对其物理起源有更多的了解。这个研究项目将让本科生兴奋地探索一种新的现象，并拼凑出一个更大的谜题的部分：星际气体的大规模搅动如何产生小范围的湍流，最终以热量的形式消散？通过与经验丰富的研究人员密切合作，学生将获得广泛的技术技能，并进一步发展他们独立探索问题的能力。使用世界上最大的射电望远镜的最先进的电子和计算机，学生将获得信心，他们有能力解决大型和复杂的问题。有机会与美国和国外的科学家合作，并在会议和出版物上报告他们的工作，将增强学生的研究经验，并为他们接受研究生培训或在技术劳动力中担任其他角色做好准备。该奖项是根据NSF的本科生机构研究计划颁发的。***

AST 0098561StinebringThe scintillation, or intensity variation, of pulsars can be used to probe the interstellar medium on sizes similar to that of the Solar System. Since scintillation is caused by slight density variations in the ionized component of the interstellar gas, a detailed study of pulsar scintillation yields information about how the interstellar gas is clumped, whether or not it exhibits turbulence, and how the density variations are initiated and sustained. These questions are central to an understanding of the dynamics of our galaxy and, hence, of other spiral galaxies like ours.A dynamic spectrum is a sequential collection of radio spectra obtained, typically, at one minute intervals for several hours. Occasionally dynamic spectra exhibit a loosely organized crisscross pattern as well as the more typical random pattern due to multiple path scattering in the interstellar medium. Recently it has been shown that when harmonically analyzed this crisscross pattern has a distinct and well-delineated signature in transform space. Dr. Daniel Stinebring at Oberlin College will explore this phenomenon using high-sensitivity observations from the Arecibo radio telescope and the new fully steerable radio telescope in Green Bank, West Virginia. By seeing how the harmonic signature is curved in frequency and time, the location of the scattering material can be determined. From this and other details of the observations, the physical size of the scattering objects can be found. This will aid in understanding the physical nature of the scattering material and in linking it to other astrophysical phenomena such as supernova remnants or the turbulent outflow from very young or very old stars. Determining the frequency of occurrence of this phenomenon as well as its variation with radio frequency will give additional insights into its physical origin.This research program will involve undergraduate students in the excitement of exploring a new phenomenon and piecing together parts of a bigger puzzle: how does large scale stirring of the interstellar gas create small scale turbulence which is eventually dissipated as heat? By working closely with experienced researchers, the students will gain a broad range of technical skills as well as further develop their ability to independently explore problems. Using state-of-the-art electronics and computers at the largest radio telescopes in the world, the students will gain confidence in their ability to tackle large and complex problems. Opportunities to collaborate with scientists in the U.S. and abroad and to report their work at conferences and in publications will enhance students' research experience and prepare them for graduate training or other roles in the technical workforce. This award is made under the Research in Undergraduate Institutions program at NSF. ***