Interstellar Scattering Disks

星际散射盘。格温博士将对星际介质中散射盘的形状及其时间变化进行射电波长观测研究。这些观测包括对脉冲星散射盘大小的甚长基线干涉测量(VLBI)，对羟基脉泽散射盘的灵敏VLBI观测，以及对船帆脉冲星散射盘中的散斑的搜索。星际等离子体中的射电波长散射限制了许多射电源观测的分辨率和位置精度，随着VLBI基线扩展到太空，天文测量VLBI的精度接近微弧秒水平，这一限制将变得更加重要。大尺度等离子体波动作为透镜，可以聚焦和散焦脉冲星和类星体的辐射，产生这些来源的观测到的低频变化。格温博士的研究旨在提高我们对散射等离子体性质的理解。

Interstellar Scattering Disks. Dr. Gwinn will carry out a radio wavelength observational study of the shapes of scattering disks in the interstellar medium and of their temporal variations. The observations include Very Long Baseline Interferometry (VLBI) measurements of the sizes of the scattering disks of pulsars over periods of years; sensitive VLBI observations of the scattering disks of hydroxyl masers; and a search for speckles in the scattering disk of the Vela pulsar. Radio wavelength scattering in the interstellar plasma limits the resolution and positional accuracy of observations of many radio sources and will become more important as a limit as VLBI baselines are extended into space and the accuracy of astrometric VLBI approaches the microarcsecond level. Large scale plasma fluctuations, acting as lenses, can focus and defocus radiation from pulsars and quasars, producing the observed low frequency variability of these sources. Dr. Gwinn's research is directed toward improving our understanding of the properties of the scattering plasma.