Large Scale Lower Ionosphere Remote Sensing

在国家科学基金会以前的资助下，国际电离层协会开发并成功地展示了一种遥感工具，它能够测量广大地理区域内较低的电离层电子密度，只需最少的地面仪器，即可利用闪电极低频率辐射的无线电探测。作为这项工作的一部分，过去五年来，杜克大学的一个站点一直在记录宽带VLF/ELF数据。此外，该小组还设计和建造了两个便携式甚低频/极低频辐射传感器和数据采集系统，最近在科罗拉多州(2005年)以及巴西北部和南部(2005年和2006年)的一些试验活动中使用了这些系统。这一新研究项目的主旨是利用这些现有数据集以及来自新的有针对性的测量活动的数据，对广泛的地理位置和时间尺度上的较低电离层电子密度变异性提供定量估计。该方案将追求一些具体的研究目标：1)测量中纬度的变率和结构，并尽可能确定产生这种变率的过程；2)测量高、低纬度D和E区的剖面，特别侧重于预计高能粒子降水影响将特别显著的南大西洋磁异常区域的测量；3)测量不同类别闪电产生的电离层扰动的高度分布，以回答有关负责机制的长期存在的问题；4)测量E区层的变异性和空间结构，以及5)将这项技术发展成适合分布式仪器阵列概念的自主分布式仪器系统。这项研究主要致力于了解大范围大气变异性及其影响，因此其本质上与全球气候变化等重要社会问题密切相关。研究生和本科生都将参与这项研究计划。

Under previous NSF funding the PI has developed and successfully demonstrated a remote sensing tool capable of measuring lower ionospheric electron densities over wide geographic regions with a minimum of ground based instrumentation based on radio sounding of very low frequency radiation from lightning strokes. As part of this effort, broadband VLF/ELF data has been recorded at a Duke University site for the last five years. In addition, the group has designed and constructed two portable VLF/ELF sensor and data acquisition systems that have been used in some recent experimental campaigns in Colorado (2005), and Northern and Southern Brazil (2005 and 2006). The thrust of this new research project is to use these existing data sets together with data from new targeted measurement campaigns to provide quantitative estimates of the lower ionosphere electron density variability over a wide range of geographic locations and time scales. The program will pursue a number of specific research goals: 1) measure mid-latitude variability and structure and determine to the degree possible the processes that drive this variability; 2) measure high and low latitude D and E region profiles, with particular emphasis on measurements in the South Atlantic magnetic anomaly region where high energy particle precipitation effects are expected to be especially significant, 3) measure the altitude profiles of different classes of lightning-produced ionospheric perturbations to answer long-standing questions about the mechanisms responsible, 4) measure E region layer variability and spatial structure, and 5) develop the technique into an autonomous distributed instrumentation system that would fit into a distributed instrument array concept. The research is devoted largely to understanding large scale atmospheric variability and its effects, and thus is by its nature closely tied to important societal issues such as global climate change. Graduate as well as undergraduate students will be involved in the research program.