Voltages observed between the ends of various underwater telegraph cables up to 9660 km long are analyzed in terms of planetary electric fields, deep ocean tides, wind driven surface currents, and geomagnetic induction.It is concluded that the average planetary electric field, which may originate from the internal processes generating the geomagnetic field, is not more than 0.038 mv/km ± 20% between Fiji and Vancouver Island. This is almost an order of magnitude less than previously reported.The average resistivity of the sea bed to a scale depth of 130 ± 20 km, treated as a single homogeneous plane layer, is 37 ± 5 ?m off the coast of Vancouver Island. This is similar to what is observed below the adjacent land.No statistically significant model was found relating the voltages on the 9660 km cable to tide heights at the shore, and geomagnetic field changes. However, it was found that the geomagnetically induced voltages between the ends of the 85 and 23 km cables were larger than the tidally induced voltages. A satisfactory model of these cable voltages was developed in terms of tidal heights, measured at the shore, and geomagnetic fields measured at a nearby observatory.All the cables were broken at sea, and the data are therefore of special interest because it is unlikely they will ever be duplicated.
Micropulsation fields measured simultaneously at pairs of stations are compared in order to describe their recognizable geographical extent and the perturbations due to local terrain. Some characteristics of coastal and inland sites are shown. The micropulsation field gradients were too small to be measured over a homogeneous earth but were clearly evident near the seacoast. Estimates are made of the extent of the anomaly at the seacoast, and of the fraction of the signal accounted for by geology of the site. Separations between sites range from 1 km up to 1750 km. The distribution of the micropulsation amplitude in different directions and its dependence on period are shown for each site. Its correlation with Kp is also shown.The data refer only to regular micropulsations of period from about 500 seconds down to 2 seconds, observed simultaneously at pairs of stations situated in mid-latitudes.
New observations are reported of the diurnal variation, direction, frequency spectrum, and geographical distribution of geomagnetic ~nicropulsations (PC and Pt). I t is argued from a conlparison of published data that these phenomena have pri~narily a solar time dependence, and may occur locally. A t our two stations, separated by 60 longitude degrees, related signals are only occasionally observed. The phase characteristics of such related signals, together with differences in directional characteristics reported by other observatories, put serious strain on recent theories of the outer atnlospheric origin of micropulsations.
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