Considering Magneto-hydrodynamic oscillations of an infinitely long cylinder of electrically conducting liquid medium rotating in a uniform magnetic field, we see that the periods of oscillations are much different from that of non-rotating cylinder, when Coriolis force is much larger than the electro-magnetic force.
We obtain two periods T₁, T₂ for one mode of oscillation
T₁>T₀>T₂
where T₀ is the period of non-rotating cylinder.

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Magnetic interaction between different constituents in each grains of ferromagnetic minerals in rocks is studied with the aid of X-ray, microscopic and chemical analyses as well as magnetic measurements. Since by means of suitable heat-treatments the degree of intergrowth of a constituent into others in mineral grains is changed markedly, the resultant magnetic interaction between these constituents is also changed appreciably. It is proved as the result of general study that the anomalous increase in thermo-remanent magnetization of ferromagnetic minerals is due to magnetic coupling of a constituent having a higher Curie-point with other one having a lower Curie-point.

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Horizontal wind systems in the ionospheric E-region are obtained from the dynamo theory of the solar daily magnetic variation on quiet days, for the case of a non-rotating earth. It is found that the main harmonicterm of ionospheric wind velocities necessary to produce the quiet-day magnetic variations is not semi-diurnal, but diurnal. The diurnal amplitude is about 30m/sec and the semi-diurnal one is about 10m/sec at low latitudes. The semi-diurnal component is nearly in phase with that of winds on the ground derived from the barometric pressure variation, and its tidal amplification is estimated as about 50. On the basis of these ionospheric winds, the vertical drift velocities of electrons in the F-region are estimated.

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