Very low, extremely low and ultra low frequency electromagnetic radiation (VLF/ELF/ULF, i.e. 30 kHz down to some milli-Hz) generated within the earths magnetosphere, ionosphere, atmosphere and lithosphere yields a wealth of information about extraterrestrial and terrestrial phenomena including gamma ray bursts, solar activity and thunderstorms. Furthermore because of its penetrating properties man made very low frequency radiation plays an important role in underwater and underground research and applications including submarine communication and remote sensing mineral contents of the terrestrial subsurface. Elaborate ionosphere heater experiments try to modulate the charged layers of our upper atmosphere with these frequencies. A detailed understanding of the propagation properties of this radiation in and around the earth can be gained using powerful numerical methods, for example FDTD and FEA (Finite Difference Time Domain and Finite Element Analysis) based solutions of the Maxwell equations. The talk gives a survey of the phenomena involved and discusses results of computer model calculations.
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