Wideband Analysis of Sources and Structure of the Earth-Ionosphere Waveguide

地球-电离层波导的来源和结构的宽带分析

• 批准号: 0337298
• 负责人: Earle Williams
• 金额: $ 61.97万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-11-15 至 2009-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337298&HistoricalAwards=false
• 关键词: Wideband; Analysis; Sources; Structure; Earth

This study is concerned with the electromagnetic waves produced by lightning and propagating worldwide in the natural waveguide formed by the conductive surface of the earth and the conductive ionosphere. Measurements are under way with a new antenna to monitor the height of this waveguide using the energy of individual lightning flashes, with the goal of detecting changes in the height. Such changes can arise from the ionizing effects of lightning flashes, or from changes in ionizing radiation from the sun or outer space. The so-called quality factor of the waveguide is also scrutinized to investigate global variations in ionizing radiation from space. A second major task involves the characterization of electrical current that flows in vertical lightning channels. The mathematical theory for electromagnetic waves in the ELF (Extremely Low Frequency) region of the electromagnetic spectrum is used in conjunction with electric field measurements to infer the history of the lightning current. These currents are then used to understand the behavior of transient luminous phenomena such as sprites, elves, and haloes, which occur over large thunderstorms.Broader scientific impacts arise from the global implications of the observations, which enable access to evidence of global change both within the waveguide (the troposphere) and external to the waveguide (the sun and outer space). The educational impacts involve the international collaboration almost guaranteed by problems of a global nature, and the entrainment of MIT undergraduate students early in their scientific careers.

本研究是关于闪电产生的电磁波在地球导电表面和导电电离层形成的自然波导中传播到世界各地。 目前正在使用一个新的天线进行测量，利用单个闪电的能量监测这一波导的高度，目的是探测高度的变化。 这种变化可能来自闪电的电离效应，或者来自太阳或外层空间电离辐射的变化。 波导的所谓品质因数也被仔细检查，以调查来自空间的电离辐射的全球变化。 第二个主要任务涉及在垂直闪电通道中流动的电流的特性。 电磁频谱的ELF（极低频）区域中电磁波的数学理论与电场测量结合使用，以推断雷电流的历史。 这些电流被用来理解在大雷暴上空出现的瞬时发光现象，如精灵、精灵和光晕。观测结果的全球意义产生了更广泛的科学影响，这使得人们能够获得波导内（对流层）和波导外（太阳和外层空间）的全球变化证据。 教育的影响涉及国际合作，几乎保证了全球性的问题，并夹带麻省理工学院的本科生在他们的科学生涯的早期。