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Three-dimensional FDTD modeling of impulsive electromagnetic propagation in the global Earth-ionosphere waveguide below 30 kHz.

机译：低于30 kHz的全球地球电离层波导中的脉冲电磁传播的三维FDTD建模。

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摘要

Wave propagation at the bottom of the electromagnetic spectrum (below 300 kHz) in the Earth-ionosphere system is a problem having a rich history of theoretical investigation extending over many decades. Propagation within this system involves complex interactions of electromagnetic waves with the lithosphere, oceans, and ionosphere, leading to resonances that involve literally the entire planet Earth. Currently, electromagnetic phenomena below 300 kHz form the physics basis of remote-sensing investigations of lightning and sprites, global temperature change, subsurface structures, submarine communications, and potential earthquake precursors.; This dissertation addresses the application of the finite-difference time-domain (FDTD) algorithm to model impulsive electromagnetic wave propagation within the global Earth-ionosphere cavity at frequencies below 30 kHz. Two generations of numerical models are presented: a latitude-longitude grid-cell arrangement, and a geodesic grid-cell arrangement. Both types of models extend from 100 km below sea level to an altitude of 100 km, and enable a direct, full-vector, 3-D time-domain Maxwell's equations calculation of electromagnetic wave propagation due to an arbitrary excitation. Furthermore, they can account for arbitrary horizontal as well as vertical geometrical and electrical inhomogeneities and anisotropies of the ionosphere, lithosphere, oceans, and Earth's magnetic field. First, the models are verified by comparing the FDTD-calculated daytime ELF propagation attenuation with data reported in the literature. Next, four example applications are provided: (1) an investigation of hypothesized preseismic electromagnetic phenomena; (2) the development of a novel subsurface radar designed to sense the presence of major oil deposits; (3) the development of a novel radar for locating and characterizing localized ionospheric anomalies within 100 km of the Earth's surface; and (4) the development of a gyrotropic ionosphere plasma model for studying electromagnetic radiation from lightning and sprites.
机译：在地球电离层系统中，电磁波频谱底部（低于300 kHz）的波传播是一个具有数十年丰富理论研究历史的问题。该系统内的传播涉及电磁波与岩石圈，海洋和电离层之间的复杂相互作用，从而导致涉及整个地球的共振。目前，低于300 kHz的电磁现象构成了对闪电和小精灵，全球温度变化，地下结构，海底通信和潜在地震前兆进行遥感研究的物理基础。本文研究了时域有限差分法（FDTD）在模拟脉冲电磁波在地球电离层空腔内以低于30 kHz的频率传播过程中的应用。提出了两代数值模型：纬度-经度网格单元布置和测地网格单元布置。两种类型的模型都从海平面以下100 km延伸到100 km高度，并且可以进行直接，全矢量，3D时域的Maxwell方程计算，该计算由任意激发引起的电磁波传播。此外，它们可以解释电离层，岩石圈，海洋和地球磁场的任意水平和垂直几何和电气不均匀性和各向异性。首先，通过将FDTD计算的白天ELF传播衰减与文献中报道的数据进行比较，来验证模型。接下来，提供了四个示例应用程序：（1）对假设的地震前电磁现象的研究； （2）开发一种新颖的地下雷达，旨在感知主要油藏的存在； （3）开发一种新型雷达，用于定位和表征距地球表面100公里以内的局部电离层异常； （4）开发用于研究雷电和子画面电磁辐射的回旋电离层等离子体模型。

著录项

  • 作者

    Simpson, Jamesina Jean.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Geophysics.; Engineering Electronics and Electrical.; Atmospheric Sciences.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 148 p.
  • 总页数 148
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;无线电电子学、电信技术;
  • 关键词

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