Diurnal Variation of the Earth's Magnetic Field at Sea

A longitudinal variation of electron drift velocity in the equatorial electrojet

“…The fluctuations occur only when the electron drift velocity relative to the ions is greater than the ion acoustic velocity; therefore their presence on spectral records is evidence that the electron drift velocity in the sampled region is greater than the ion acoustic velocity, Although the eastern spectra in [1964], Weaver [1963], and Panamaray [1960] indicate that the presence of a coastline would produce a measurable effect on standard ground-based magnetic recordings. Anomalously large magnetic variations have been observed near coastlines in midlatitudes [Hill and Mason, 1962;Nagata, 1951], as well as in arctic [Wescart, 1967;Zhigalov, 1960] and antarctic [Mansurov, 1958] $ --1.4ø), 20($ --2.9ø), and 13($ --4.3ø), respectively. The solid curve is assumed to be the most probable in both sets.…”

The Effect of an Ocean on Magnetic Diurnal Variations

“…Various writers have reported the observation of anomalously large diurnal and short-period magnetic variations in the vicinity of the edge of a large body of sea water. At the edge of the continental shelf in the north-east Atlantic, Hill & Mason (1962) observed diurnal variations having amplitudes almost twice as great as those measured by land-based equipment in similar latitudes . Ponomarev (1960) and Mansurov (1958) have noted increases in the amplitude of magnetic variations at the shoreline near the Antarctic base Mirny, and Zhigalov (1960) has reported similar effects in the Arctic Ocean.…”

“…Since this investigation was originally prompted by the observations of Hill & Mason (1962) at the edge of the continental shelf in the western approaches to the English Channel, we have computed solutions on the EDSAC I1 computer of the Cambridge University Mathematics Laboratory using parameters which correspond roughly to the dimensions of the Atlantic Ocean in that neighbourhood. Using the following dimensions : depth of ocean = 5 km width of ocean = 4 ooo km = 55 degrees longitude depth of mantle = 600 km conductivity of sea water = 4 x 10-11 e.m.u., we obtain for the non-dimensional parameters :…”

Effect of an ocean ridge model on geomagnetic variations

“…on, 1971) may have applications to this problem. It is even possible that at some places conditions would be appropriate for observing the variation anomaly by using the method of Hill and Mason [1962] in which a total-field recording magnetometer is floated on the ocean surface in a buoy.…”