Studies of Plasmashere Boundary Layer with Distributed Arrays of Radio Instruments

该奖项由2009年《美国复苏和再投资法》(公法111-5)资助。等离子体层边界层(PBL)是耦合地球电离层和磁层的中纬度动态过程的关键区域。这个区域分隔了两个不同的等离子体流动体系，一个朝向太阳对流，另一个与地球共同旋转。这一区域动力学的一些后果是电离层、等离子体层和磁层耦合的电场的发展，热等离子体的结构和重新分布，以及不同尺度大小不规则性的形成。了解PBL现象的性质，包括它们的大小和时空特征，对于描述PBL区域及其潜在的地球物理特征至关重要。该项目的主要研究目标是对PBL进行实验研究，以表征其在一系列地磁条件下从微到中尺度(米到1000公里)的电子密度梯度、扰动、流动和电场。该项目的第二个目标是开发和调查用于观测电离层的小型无线电仪器分布式阵列的能力。这些调查将在即将到来的太阳周期上升阶段继续进行。将解决的主要科学问题是：1)在中纬度形成密度不规则导致闪烁的位置和频率？2)在地磁扰动条件下中纬度风暴增强密度(SED)特征的发展是否与季节、经向或太阳周期有关？3)PBL电场的强度和变化是什么，以及它们如何随地磁条件变化？这项研究将在太阳周期的上升阶段利用现有的分布式仪器阵列，以合作活动为导向的方法进行独特的实验观测。数据将从全球定位系统接收器网络和最近部署的电离层科学阵列截获信号中获得。GPS网络提供来自世界各地的总电子含量(TEC)信息。ISIS阵列基于高性能相干软件无线电接收器，可以截获范围很广的信号，并具有极其精确的时间和频率同步。截获的信号可用于传播研究、频谱监测、闪烁观测、无源雷达和多基地有源雷达。其目的是确定分布式科学仪器阵列，如全球定位系统和国际空间信息系统在大气系统科学调查中的作用。分布式阵列能够在大范围内以高空间和时间分辨率显示大气信息。该项目的更广泛影响有几个。其中几项研究活动将纳入麻省理工学院干草堆天文台现有的教育计划，包括本科生研究经验(REU)、教师研究经验(RET)和高中实习。学生学习的一些领域包括高性能计算、实时信号处理和科学数据挖掘。ISIS的节点位于康奈尔大学、锡耶纳学院、达特茅斯学院和华盛顿大学，这项研究将加强这些机构的合作和教育推广活动。这项研究的其他影响包括建立一个大型电离层观测数据库。ISIS阵列和GPS TEC测绘都将提供诊断，帮助了解急剧TEC梯度对空间天气的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The plasmasphere boundary layer (PBL) is a critical region for dynamic processes in the mid-latitudes that couple the Earth's ionosphere and magnetosphere. It is the region which separates two distinct plasma flow regimes, one convecting sunward, the other co-rotating with the Earth. Some of the consequences of the dynamics in this region are the development of electric fields which couple the ionosphere, plasmasphere, and magnetosphere, the structuring and redistribution of thermal plasmas, and the formation of different scale-sizes of irregularities. Understanding the nature of PBL phenomena, including their magnitude and spatial and temporal characteristics, is critical to characterizing the PBL region and its underlying geophysics. The primary research goal of this project is to experimentally investigate the PBL to characterize its electron density gradients, perturbations, flows, and electric fields from micro to meso-scales (meters to 1000 km) under a range of geomagnetic conditions. A secondary goal of the project is to develop and investigate the capabilities of distributed arrays of small radio instruments for observations of the ionosphere. These investigations will continue through the upcoming rising phase of the solar cycle. The primary scientific questions that will be addressed are: 1) where and how often do density irregularities form at mid-latitudes that result in scintillation?, 2) is there a seasonal, longitudinal, or solar cycle dependence in the development of mid-latitude storm enhanced density (SED) features during geomagnetically disturbed conditions?, and 3) what are the strengths and variations of PBL electric fields, and how do they vary with geomagnetic conditions? This research will exploit existing distributed instrument arrays during the rising phase of the solar cycle to make unique experimental observations in a collaborative campaign oriented approach. Data will be obtained both from the Global Positioning System (GPS) receiver network and from the recently deployed Intercepted Signals for Ionospheric Science (ISIS) array. The GPS network provides total electron content (TEC) information available from many locations around the world. The ISIS array is based on high performance coherent software radio receivers which can intercept a wide range of signals with extremely precise time and frequency synchronization. The intercepted signals can be used for propagation studies, spectrum monitoring, scintillation observations, passive radar, and multistatic active radar. The intent is to establish the utility of distributed arrays of scientific instruments, such as GPS and ISIS, in system-science investigations of the atmosphere. Distributed arrays enable the visualization of atmospheric information with high spatial and temporal resolution over large areas. The broader impacts of the project are several. Several of the research activities will be incorporated into existing educational programs at the MIT Haystack Observatory, including the research experience for undergraduates (REU), the research experience for teachers (RET), and high school internships. Some of the areas of student effort include high performance computing, real-time signal processing, and scientific data mining. ISIS nodes are located at Cornell University, Siena College, Dartmouth College, and University of Washington and the research will enhance collaboration and educational outreach activities at these institutions. Additional impacts of this research include the creation of a large database of ionospheric observations. Both the ISIS array and GPS TEC mapping will provide diagnostics which aid understanding of the space weather impact of sharp TEC gradients.