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Analysis of Magnetotelluric Micropulsations at Widely Separated Stations

出版	Air Force Cambridge Research Laboratories, Office of Aerospace Research, United States Air Force, 1964
URL	http://books.google.com.hk/books?id=fby40MvkoQcC&hl=&source=gbs_api
EBook	FULL_PUBLIC_DOMAIN

註釋An investigation of ultra low frequency electromagnetic signals known as magnetotelluric micropulsations was made. The electric field strength at the earth's surface was measured by means of electrodes placed in the ground. Analog paper chart records of these signals were made at Trinidad, B.W.I., Puerto Rico, and Austin, Texas. These records were later hand-digitized. The power spectra of the signals at each station were computed for a data sample three quarters of an hour long. Certain power spectral peaks in the frequency range from .01 cps to .25 cps were noted. Several previously undiscovered regularities in the spectra of this sample were found. Power spectral peaks occurred at .05, .125, .175, and .225 cps. Also computed were coherencies between signals at all stations. Coherencies above .8 were found between signals recorded at stations more than 2,000 miles apart. The regular features found in the power spectra were also noted in the coherencies. In addition, some spectral line splitting was not obvious in the power spectra appeared in the coherencies. From the evidence presented it is concluded that certain frequency bands of micropulsations are simultaneous over great distances, and probably originate in the outer atmosphere. (Author).