Data from three-axis magnetometers situated at two different locations on a north-south line from Churchill were fed into a PDP-8 computer at Churchill. The altitude, horizontal position and intensity of the polar electrojet were determined in real time to select the optimum launch time for rockets used to study auroral phenomena associated with substorms. During the two substorms studied, the jet was located near 140km altitude and the intensity of each was as high as 0.5 megaamps. In one case, both stations gave results similar to the two station fit, so the jet was well approximated by a line current. In the second case, the data suggest that the current was either a sheet current or a group of filaments.

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The effect on f₀F₂ of daytime sudden commencement and nighttime sudden commencement storms is shown for equatorial, low-, mid- and high-latitude locations. It is seen that it is the mid-latitudes which show the greatest dependence on time of sudden commencement, and larger increases of F-region ionisation are seen in the evening to midnight hours as compared to day following a storm. Such prominent differences are not seen at the other latitudes. The mid-latitude observations are interpreted in terms of neutral thermospheric winds, and magnetospheric electric fields set up during disturbed conditions.

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Several alternative analyses of the steady state solutions of coupled modes have been proposed. In determining which, if any, steady state solution is of physical significance, the manner in which the hydromagnetic system evolves from an initial disturbance would be decisive. The basic initial value problems are those of field line excitation and relaxation. These two cases correspond to the energy being initially in the poloidal or toroidal modes. These difficult problems are investigated by establishing the relevance of a simple mechanical analogue which is studied in detail. This is accomplished in three stages: (a) a rectangular model of the plasmasphere is described and its physical characteristics are compared with those of a dipole field magnetized plasma; (b) a mechanical system is derived consisting of an elastic string with each point of which is associated an oscillator. For the symmetric modes with weak ioncyclotron coupling, the wave equations for the hydromagnetic and mechanical systems are essentially identical; (c) the mechanical system is reduced to an elementary wave-oscillator model representing the coupling between resonant poloidal and toroidal modes. The characteristic motion of the simplified system is independent of the strength of the coupling. The solutions suggest that resonant field lines tend to reflect an incident poloidal wave and transmit only an evanescent wave. The toroidal mode does not become singular but attains a finite amplitude in performing this reflection. In general, it is concluded that the behavior of coupled and uncoupled modes is essentially different. When any coupling is present, steady state solutions, as normally understood, are not possible.

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Characteristics of atmospheric tidal oscillations in viscid atmosphere are discussed. When the effect of thermal conduction is included, the equations of the oscillations remain separable with the Hough function as in the classical theory. The vertical structure of the oscillation is given by a fourth-order differential equation. The equation has two kinds of solutions. The one is modified tidal mode and the other is thermal conductive mode. On the other hand, viscous term does not make the equations separable because of the horizontal dependence of the Coriolis force. Approximately, a constant Coriolis force model is used. The horizontal structure is given by the associated Legendre function. The vertical structure is given by a sixth-order differential equation. Two kinds of viscous modes emerge under the Coriolis effect. If the thermal conductive term is also included, an eighth-order differential equation is obtained. Characteristics of the modified vertically propagating tidal modes are that the vertical wavelengths become long and the damping factors become large with increasing kinematic viscosity. The viscous and thermal conductive effects on the nonpropagating tidal modes are to modify their rate of decay to be slightly smaller. The diurnal viscous and thermal conductive modes with negative equivalent heights become important above the height of 140km because the damping factors decrease with increasing kinematic viscosity, and especially the former mode has similar characteristics to those of the vertically propagating tidal modes. The effect of viscosity on diurnal thermospheric wind is also discussed to investigate the physical meaning of the viscous wave.

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The diurnal variation of phase and amplitude of NWC-22.3kHz signal is investigated. Typical pattern of the phase variation and amplitude fading during sunrise transition, for the case of the summer season in the northern hemisphere, is interpreted in terms of waveguide modes interference. By considering the second mode propagation besides the first in daylight, a good agreement between theoretical and experimental results is obtained.

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Paleointensity studies by the methods of the Thelliers, Wilson, and van Zijl were compared for adjacent specimens from each of five basaltic lava flows. For three of the flows, the actual paleointensity is independently known within ±6%. All specimens had Curie temperatures above 500°C, and those from four of the flows had lower Curie temperatures as well, indicating they probably underwent varying degrees of high-temperature oxidation and disproportionation during initial cooling. These four suffered irreversible changes in their blocking temperature spectra when heated in air above 400 to 500°C. Nonetheless, the paleointensities derived by the Thelliers' method below these temperatures agree with the actual values within the uncertainties. The values obtained by the other methods are not as accurate or reliable. In four out of five lavas, A. F. cleaning of 100 to 200 oe prior to each measurement of remanence in the Thelliers' method degraded the results for determination of paleointensity.

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Results of paleomagnetic studies of twenty-four flows sampled from the area between Jabalpur (23°11′N, 77°58′E) and Dindori (22°57′N, 81°00′E) in the northeast part of the Deccan trap exposure are presented. The elevations of the flows varied from 372m to 670m above mean sea level. The results reveal the presence of a field reversal quite different from the one studied by earlier workers. Presence of this field reversal has been recently indicated by PAL et al. and WENSINK, in the Malwa and Nagpur regions, respectively. A comparison of the paleomagnetic results of the Deccan volcanics from different areas with those of normal polarity from Jabalpur-Dindori region indicates that the land mass of India drifted northward by about 21° during the entire period of the igneous activity represented by the Deccan traps.

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A core 197.2m long was taken from the central region of Lake Biwa. About 10000 serial specimens were prepared from the axis of the core to study palaeomagnetism. They have remanent magnetization stable enough to allow us to decipher the geomagnetic field of the past. The palaeomagnetic results are shown in detail down to 30m from the top of the core. The age of this depth is estimated at about 60000yr B. P. Smoothed curves of magnetic inclination and intensity as functions of depth are obtained by a seven-point moving average, reflecting the variation of the past geomagnetic field.

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