The development of the main phase of geomagnetic storms and of magnetic and auroral substorms is examined on the basis of analyses of individual geomagnetic storms. Several important aspects of geomagnetic storms revealed in this study are reported and discussed.

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An approximate method for analyzing broad-scale current systems in the ionosphere is outlined which allows calculation of sources and sinks of current from surface observations. Suchs ources and sinks of ionospheric current have been suggested in connection with models for geomagnetic disturbance phenomena. Usual analytic methods yield only divergence-free current systems. The treatment of these current systems by the methods outlined yield the desired divergences of the sheet-current in the ionospher.

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The use of the first and second adiabatic invariants of charged particle motion in calculating the trajectories of particles drifting in combined magnetic and electric fields is discussed. Such calculations become particularly simple for a dipole magnetic field if the magnetic lines of force are electric equipotentials.

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The increase in the temperature and density of the upper atmosphere during geomagnetic storms is discussed. The latitude dependences of various phenomena related to storms are examined in an effort to determine the latitude dependence of the neutral heating, which is not well determined by the drag of satellites. The energy balance in the auroral zone during storms is also discussed.

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Simulated predictions of geomagnetic storms are made, using polar cap absorptions derived from the IGY ionosonde records for two stations on each polar cap, published by Jelly and Collins. The larger storms are “predicted” 70 percent of the time, and the smaller storms 40 percent. This method (using only four stations) is incapable of predicting the size of the storm, although an earlier study using Hill's ionosonde data from 70 stations in the Northern Hemisphere indicated the size of the following storm fairly well. Several other methods of rapidly detecting solar emissions or polar cap absorptions are examined with regard to their utility as predictors of geomagnetic storms.

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The authors demonstrate by analysing data for 1960, 1961 and 1962 that daily planetary index of geomagnetic disturbance K_p≥25 occurs about as often with decreases (dI/dt<0) as with increases (dI/dt>0) of daily mean intensity of galactic cosmic rays measured on the earth.
They have studied the association of these two types of K_p≥25 epochs and of International Quiet Days with the central meridian passage of long lasting zones of activity in the corona at the solar equator.
The authors suggest that high K_p is caused by two distinct types of interplanetary conditions, (a) the passage of a corotating shock front or a radially advancing blast wave, and (b) the emergence of the earth from a cavity as proposed by Sarabhai considering the consequences of nonuniformity of solar wind velocity.
The occurrence of an International Quiet Day is related to c. m. p. of the intermediate point of declining intensity on the trailing edge of a bright coronal zone which should produce a cavity (a region of reduced plasma density and weak magnetic field) where slow plasma does not catch up with fast plasma in front of it.

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The lunar geomagnetic variation field, L, was studied based on all available results of lunar analysis from a total of 37 stations. Taking into consideration the electromagnetic induction effect within the earth, spherical harmonic analyses were made for three seasons, and corresponding equivalent overhead current systems were obtained by the separation of the external and internal origins.
The L current system including the lunar equatorial electrojet derived shows that the total current intensities during equinoxes and particularly winter are larger than those of previously obtained systems. The ratio of the total current intensity in summer and winter is less than two, and the intensity during equinoxes is similar to that in summer.

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The atmospheric dynamo mechanism associated originally with ionospheric winds is extended to include the effect of the solar wind, being now called a generalized dynamo mechanism. The daily geomagnetic variations are summarized and classified on the basis of this generalized dynamo mechanism, and the method of mathematical formulation of the mechanism is briefly discussed by taking into account the electric linkage between geomagnetic conjugate points and also between the ionosphere and the magnetosphere.

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Rubidium-vapor magnetometers were flown to altitudes near 150km over Wallops Island, Virginia in three Nike-Apache Rockets. One flight was made at a time when no ionospheric current was expected and none was encountered. The other two flights measured a current sheet with lower edge at 105m and upper edge at 123km, with the total current being in agreement with that expected from the ground observations.

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Electromagnetic coupling between an ionosphere and an underground cylinder is studied on the basis of a perfect conductor model. It is found that an anomalous field of external origin amounting to about 10 per cent of the field of internal origin is given rise to for a typical arrangement of the conductors.

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Reviewing important classical results of studies on the geomagnetic solar flare effect (s. f. e.), it is confirmed that the geomagnetic s. f. e. is a temporary augmentation of the geomagnetic daily variation field in the sunlit hemisphere. By taking into account the electromagnetic induction within the ionosphere, it is then stressed that the geomagnetic s. f. e. be considered as a transient phenomenon in the ionosphere having about 5×10^-8 emu in integrated conductivity.
Results of analyses of global distribution of 15 typical s. f. e. 's during the IGY have shown that (a) an almost perfectly simultaneous relationship holds among optical and radio solar flares, geomagnetic s. f. e. 's and sudden ionospheric disturbances; (b) a geomagnetic s. f. e. of small amplitude takes place in the dark hemisphere always simultaneously with an s. f. e. in the sunlit hemisphere; and (c) the maximum peak of s. f. e. does not always occur simultaneously at different locations but it is more retarded with increasing solar zenith distance in the sunlit hemisphere for some weak s. f. e. The two new characteristics of s. f. e., (b) and (c), are interpreted as results of transient increase in the electric conductivity of the lower ionosphere in the sunlit hemisphere caused by an X-ray solar flare.

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A review is presented of some of the more important properties of Pc 1 (0.2-5cps) emissions observed at middle and low latitudes. Special attention is given to fine structured regular oscillations referred to by various workers as Pearls, Type A Oscillations, and Hydromagnetic (Hm) Emissions. The following aspects of these oscillations are discussed.
a) Signal Appearance. The emissions are considered from both their amplitude-time (waveform) appearance observed on chart records and their frequency-time (f-t) characteristics observed on sonagrams. The various types of f-t fine structure are discussed (rising and falling frequency elements, fan shaped elements, etc.).
b) Simultaneity of Occurrence at Widely Separated Locations. A high degree of similarity is often found in the appearance of f-t structural elements of hm emissions recorded simultaneously at widely separated stations. Attention is given to the time-shifts between these elements at stations in the same hemisphere and in opposite hemispheres.
c) Times of Occurrence. Correlations are considered between times of occurrence of hm emissions and other geophysical effects such as charged particle events, magnetic storms, and variations of the ionospheric parameter F₀F₂.
d) Latitude Effects. Various latitude dependent emission characteristics are discussed. These include latitude variations of emission frequency, fine structure repetition period, and signal amplitude.
In addition to the aspects of the Pc 1 emissions outlined above, properties of two other types of emissions are briefly discussed. One of these signals, referred to here as a “continuous emission” also lies in the Pc 1 category. It is often observed continuously throughout the night and is characterized by a slow variation of f-t characteristics. The other signal, which might be placed in a Pc 1-Pi 1 transition category, is observed during magnetically disturbed periods. On sonagrams it is characterized by an irregularly spaced rising frequency fine-structure. When monitored aurally on time-compressed magnetic tape (speed-up factor of 1000-2000), it is characterized by a sound similar to bubbles blown under water.

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Recent experimental and theoretical work suggests the hypothesis that hydromagnetic (hm) emissions are hydromagnetic wave packets guided by field lines as they bounce back and forth between hemispheres of the earth. As such they are analogous to whistlers, and one test of the hypothesis is the quantitative calculation of plasma densities in the outer magnetosphere and their comparison with whistler densities closer to the earth.
Many hm emission exhibit measurable dispersion when displayed in the form of sonagrams (frequency vs time displays). In such cases, the measurement of group bounce times at two different emission frequencies can be combined with an accurate model of the magnetosphere to determine the zero-frequency (Alfvén) bounce period and the equatorial cyclotron frequency above which the wave cannot propagate. These two quantities uniquely define the field line along which the hm emission propagated and the integrated plasma density along that field line.
Analysis of 9 events showed they occurred on field lines crossing the equatorial plane between 4 and 10 earth radii, and showed equatorial plasma densities in agreement with extrapolated whistler “knee” densities.

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As shown in previous paper (Maeda and Watanabe), periodic heating around E-region in the polar upper atmosphere by auroral particles can be regarded as the source of very long acoustic type atmospheric pressure waves observable at the ground. It was shown, however, that these pressure waves attenuate rapidly outside the source in the isothermal atmosphere. On the other hand, in the actual atmosphere, these waves propagate horizontally through the ducting, which consists of two channels, corresponding to the atmospheric temperature minima at the mesopause and the tropopause, respectively. It is shown that for the propagation of 100sec waves, upper channel is effective in summertime, while lower one is effective in winter in the polar upper atmosphere. It is also shown that the traveling pressure waves associated with auroral activity is not necessarily limited in the acoustic mode, but sometimes extended to gravity (thermobaric) mode. This is partly due to the existence of large positive lapes rates layers such as upper part of stratosphere and in the thermosphere. As a consequence, clear sinusoidal oscillations, which appear occasionally with periods of group velocity minima (around 5min), can be ascribed to Airy phase. As an example, the data obtained at the NBS-stations in Washington, D. C. on July 15, 1960 are shown with its preliminary results of power spectrum.

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Recent rocket measurement of the spectrum and altitude distribution of the visible dayglow are reviewed. The current theory of the daygolw is discussed in the light of these data and the results of new laboratory studies on atomic processes of aeronomic interest. The important role played by solar radiation in the excitation of the visible dayglow is illustrated in a detailed discussion of the emission of the (0, 0) negative band of N₂⁺ and the red line (6300A) of atomic oxygen in the dayglow.

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