Measurement of Fluctuating Magnetic Gradients Originating from Oceanic Internal Waves

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Science  28 Sep 1979:
Vol. 205, Issue 4413, pp. 1381-1382
DOI: 10.1126/science.205.4413.1381


Fluctuating magnetic gradients over oceans come from electric currents flowing in seawater arising from its motions across the earth's magnetic field. Gradients of 0.3 to 0.6 picoteslas per meter for each meter of internal wave displacement have been measured at frequencies of 2 to 5 millihertz with a superconductive magnetic gradiometer supported 7 meters above the surface of water 18 meters deep about 1.5 kilometers offshore from San Diego, California.