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The Coupling of Atmospheric Electromagnetic Fields

FIGURE 3.5 Electromagnetic processes of natural origin in the ELF range. (From König et al., 1981.)

As shown in Figure 3.5, in nature, there are mainly three types of naturally occurring ELF electric

felds. Type I shows the SR waveform at 8 Hz. Type II is the wave form of naturally occurred local varia­

tion of electric felds at 3–6 Hz, and type III shows local variation at about 0.5–2 Hz. Type IV is feld fuc­

tuation as a result of thunderstorm activity. a is the feld, thunderstorm not yet visible on the horizon, b

is thunderstorm on the horizon. Type V is the signals of sunrise.

Te earth frequency was frst mentioned by Fitzgerald in 1893 (Fitzgerald, 1893). Tesla also mentioned

this frequency in 1905 (Tesla, 1905, 2015; Jackson, 1998). He presented the idea of the earth as resonat­

ing circuit as the lowest resonant frequency as 6 Hz. He described generation and detection of these low

frequency waves. He was quoted as follows: