In order to investigate the effect of non-uniform ionospheric conductivity distributions on high-latitude magnetic pulsations, a general method based on the Fourier expansion is developed. The method is applied to the incidence of Alfvén waves with a horizontal wave length of the order of the characteristic width of the non-uniform region. It is found that if at least one of the height-integrated Pedersen and Hall conductivities has a non-uniform horizontal distribution, a new component of the ground magnetic field due to non-uniformity is built up and becomes comparable to the ordinary component free from non-uniformity in a large conductivity gradient. The phase of the new component of the ground magnetic field shifts about 90° from that of the ordinary component. It is also found that the non-uniformity does not affect the distribution of the field-aligned current so much as that of the ground magnetic field.

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Measurements of sferics background noise on long-life balloon receivers at middle to very high latitudes show interesting effects explicable in terms of earth-ionosphere waveguide propagation from low latitude sferic sources. For propagation over thick (>2km) ice in day-time the measured attenuation was (22±6) dB/km.

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Signals at tidal frequencies are observed in magnetic fluctuations recorded along a line of sites spanning the region from inland Australia to the floor of the central Tasman Sea. Assuming the site furthest inland to be free from oceanic tidal effects, the M₂ signal at 1.93cycle·day^-1 at each other site along the line is separated into a part due to a tidally-driven ionospheric dynamo, and a part due to a tidally-driven oceanic dynamo. Two factors are crucial to the separation method: the recognition that the ionospheric dynamo produces frequencies (known as the partial tides, and the phase-law tides), not associated with the oceanic dynamo; and the construction and use of an ionospheric induction transfer function, taken to be constant from continent to ocean.
The separations thus carried out show that for the deep-ocean sites in the Tasman Sea, the ionospheric dynamo and the oceanic dynamo make comparable contributions to the horizontal fluctuations observed at the frequency of the M₂ tide. The vertical fluctuation component at this frequency is almost entirely due to the oceanic dynamo. There is agreement with some features predicted by theoretical models.

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A paleomagnetic study was performed on sedimentary rocks in the Ogcheon zone. The area is unique in the southern part of the Korean Peninsula for the existence of a sequence of sedimentary rocks from the Cambrian through the Jurassic periods. Although the rocks were strongly overprinted with a secondary magnetization, detailed thermal demagnetization was effective in isolating a component with a very high blocking temperature in a few sites. This component is thought to be the primary magnetization. The paleomagnetic directions from these sites, which are Carboniferous, Permian and Triassic in age, suggest that the Ogcheon zone had belonged to the South China Block rather than the North China Block.

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Sea-bottom topography, magnetic and gravity anomaly maps were compiled for two seamounts, Smt-948 (23.7°N, 151.9°E) and Smt-1100 (22.8°N, 153.4°E) in the vicinity of Minami-Tori Sima (Marcus) Island based on survey data observed by the S/V Takuyo of the Hydrographic Department of Japan from July to August, 1985. These flat-topped seamounts are located in the Jurassic magnetic quiet zone on crust older than 150Ma. On Smt-1100, sea bottom photographs were taken with a deep-sea camera and three dredge hauls were made. Three-dimensional magnetic analyses of Smt-948 gave a paleomagnetic pole position of 57.5°N, 329.5°E with the goodness-of-fit ratio 2.83. The pole position lies in the Pacific apparent polar wander path between the Late Jurassic (150Ma) and the Late Cretaceous (65-94Ma). This result implies that Smt-948 was generated in the middle Cretaceous, a significant period after the formation of the Jurassic sea-floor. Two-dimensional modeling of magnetic and gravity anomalies across these seamounts reveal a caldera-like basement structure, suggesting a constructional origin of the flat top of the guyot. A sequence of normal and reversed magnetic polarity layers is estimated from magnetic modeling on Smt-1100.

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An improved method for measuring the anomalous magnetic moment produced by mineral alteration during heating of archaeomagnetic samples is described. After subtraction of the anomalous moment the ancient geomagnetic field deduced from the data becomes reproducible to about ±5%.

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