Very-Low-Frequency Propagation Below The Bottom Of The Sea

Very-Low-Frequency Propagation Below The Bottom Of The Sea...

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1963 Mott and Biggs: VLF Propagation Below Bottom of Sea 393 After the nth iteration, we get For case of small losses, (gl>>E1, g2<<e), we have I F’I isless thanunity,andthe process will converge. However, F‘ will be close to - 1, and consecutive values of {2 will oscillate around the correct value (20. By modifying procedure so that after two first steps computer calculates and then follows the same cycle, we can apply same reasoning on (1 + F’) F’/2 as previously on F’. small loses, we get It is obvious that this modification will bring about a faster convergence, at least for small losses, and it turned out to be adequate for all values param- eters used in computations. ACKNOWLEDGMENT The author is grateful for the assistance given by group at TRG under direction of J. Nihen, and for many helpful suggestions given by F. J. Zucker of AFCRL Dr. A. F. Kay of TRG. Very-Low-Frequency Propagation Below Bottom of the Sea* H. AJOTTt, SENIOR 1\IIEMBEB, IEEE, Ah?) A. iv. BIGGSS, MEXBER, IEEE Summary-Radio-wave propagation at very low frequencies (VLF) in the stratified rock below the bottom of the sea is studied. A reasonable assumption of extremely low electrical conductivity in the stratified rock is based upon available geological data. The sur- face wave traveling along the interface between this region of low conductivity andthe highly conducting sea is compared with the vertically polarized ground wave found in VLF radio-wave propa- gation at the surface of the earth. When extremely low frequencies (ELF) are transmitted, the highly conducting layer found at greater depths below the bottom of the sea forms the lower surface of a spherical waveguide. This waveguide at ELF supports a propagation mode similar to mode existing at between the surface of e6 the lower boundary of the ionosphere. The similarity in propagation mechanisms leads name “inverted ionosphere” (described by Wheeler 111) for the underground region. sea or relatively highly conducting soil at the surface of the earth is an almost impregnable shield against atmospheric noise effects from sudden ionospheric disturbances or solar flares. In addi- tion to providing a noise-free medium, the sea has advantage that construction costs are much less than those of a transmitter the earth’s surface. * Received Kovember 15, 1962; revised manuscript received January 12, 1963. Tuscaloosa; formerly of the Aero-Space Division, Boeing Company. f Electrical Engineering Department, University of Alabama, Seattle, IVash. - . -. 1 Aero-Space Division, The Boeing Company, Seattle, \‘ash. Presumably communication between shore installations and sub- marines on the floor of the ocean could be achieved with the inverse ionosphere. The power requirement for such communication with existing transmitters the earth’s surface renders such trans- mission unattainable.
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This note was uploaded on 05/11/2011 for the course ELECTRONIC 005 taught by Professor Haghbin during the Spring '10 term at Sharif University of Technology.

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Very-Low-Frequency Propagation Below The Bottom Of The Sea...

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