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The telluric current data of Macquarie Island show complete polarization of the induced electric field. This phenomenon can be explained by assuming that Macquarie Island is an insulator imbedded in the highly conducting sea with a uniform electric field over the dimensions of the island. The theory and data show the electric field to be perpendicular to the long axis of the island. The magnetic component perpendicular to the electric field correlates with the electric field very well, suggesting that the small island does not affect the frequency response between the magnetic and electric fields.

Much of Alaska lies in or near the auroral zone, where magnetic and telluric current disturbances are large compared to those at lower geomagnetic latitudes. Pronounced and different diurnal variations of disturbance are evident from analysis of K indices from Barrow, College, and Sitka magnetic observatories. The quietest period for magnetic or electrical surveying is the late morning and afternoon hours locally. Recordings of telluric current disturbances can be used as a sensitive indicator of ionospheric activity. The large amplitude and rich frequency spectrum of the telluric currents suggests their use as a prospecting tool in Alaska.

The conjugacy of bay-type magnetic variations at midlatitude was investigated using data from the Cold Bay, Alaska, and Oamaru, New Zealand, pair (L = 2.6). Of twenty-four intervals representing positive bay activity which were examined, the majority showed substantial agreement. Eleven intervals could be considered anomalous in all or some features. At midlatitude positive bays seem to result from the return current part of auroral zone electrojets. Intervals showing noncorrelation indicate departures of the primary electrojet from a conjugate pattern. Short period magnetic pulsations were also observed as a conjugate phenomenon. They could not be studied in detail owing to the insensitivity of the magnetometers.

Electrically neutral, luminous clouds are a by-product of chemical releases conducted to create barium ion clouds for the measurement of electric fields. Wind measurements provided by the motions of these clouds are particularly valuable in that the motions can be directly compared with convective ion drift motions to test the importance of ion drag forces. Motion from multiple releases between 200 and 300 km from 15 rockets launched from four high-latitude locations is analyzed in this paper. The observations in the evening and midnight hours at magnetic latitudes above 65 deg strongly suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. In the morning sector, it is evident that neutral wind observations cannot be directly interpreted in terms of ion drag; other factors must be considered.

The electric field vectors associated with telluric currents are known to vary in relative magnitude and principal direction at different locations. A number of temporary recording sites were occupied in the College, Alaska, region, where telluric currents have been recorded routinely since 1955. The results of this study show that the relative magnitude may change by a factor of 5 and that the principal direction may range over 33° and in one extreme case 70°, in the area of radius 10 miles from the Geophysical Institute. Model studies using a two-dimensional resistor network were made to determine the effects of some simple topographic and conductivity configurations on the telluric field.

The largest change in apparent resistivity observed across a 3.3 km galvanic resistivity array during the first year of operation was 6%. This 6% decrease is strongly correlated with several months of continuous rain. Fluctuations in apparent resistivity appear to be larger after than before the rain. This is believed to be the result of a newly formed surface layer of high conductivity. No correlation is observed between local seismicity and resistivity.

Data from the L = 1.4 conjugate pair San Juan, Puerto Rico, and Trelew, Argentina, were used to study the conjugacy of low latitude magnetic variations. The majority of low latitude variations have essentially a worldwide distribution. Positive bays, however, are more limited in areal extent, and are thus of interest to a study of conjugacy. All bays examined showed similar and simultaneous variations at the conjugate stations.

The magnetic variations at a pair of geomagnetically conjugate stations, Kotzebue, Alaska, and Macquarie Island, have been studied during two days in March 1958 when auroras were observed to occur simultaneously, and in similar forms, in conjugate areas. The correlation of the variations in H and D at the conjugate stations during the periods of auroras, and also during the rest of the time studied, is very good. This evidence supports the theory that, at least during certain periods, ionospheric events in the northern and southern hemispheres are closely linked by the magnetic field lines.

High latitude magnetic disturbances and accompanying auroral displays are obvious evidence of the release of large amounts of energy, presumably from the magnetosphere and magnetotail regions. Until recently experimental efforts towards understanding these phenomena were directed toward measurement of magnetic fields, energetic particles, optical emissions, and the morphology of the observables. The importance of ionospheric and magnetospheric electric fields was recognized in theoretical studies, but actual measurements were not available due to the lack of suitable techniques. In the past several years valid electric field measurements have been made from sounding rockets and satellites with long antennas (Aggson, 1969; Maynard and Heppner, 1970). Another method more suited for making E field observations simultaneously at several points and for extended times at a given location was developed at the Max Planck Institut (Foppl et al., 1967). Barium vapor released from a sounding rocket above about 150 km partially ionizes and produces a visible ion cloud during twilight which can be tracked photographically. The ion cloud drifts under the influence of the electric and magnetic fields, and it can be shown that the velocity of a small cloud above 200 km altitude is given essentially by v = E x B/B 2. Inverting this equation to E= - v x B, the measurement of v in a known magnetic field B gives E. The GSFC-NASA Ba release experiments have produced high latitude observations of 23 ion clouds in the auroral zone and 12 in the polar cap region. From these observations we can draw conclusions about the nature of the ionospheric electric fields and the tensor conductivity elements that are most effective in producing ionospheric currents. The measurements also test the usual assumption that the surface magnetic disturbance is explained by ionospheric currents. From ground based magnetometers a typical equivalent ionospheric current pattern for the polar cap and auroral zone disturbance can be inferred. Figure 1 shows a diagram illustrating the essential features. Our E field investigations have sampled four regions of interest: (a) in the westward electrojet or negative magnetic bay region, (b) in the eastward electrojet region, (c) in the transition region where the westward electrojet passes polewards of the eastward jet, and (d) in the polar cap region. Visible auroral displays were observed in the Ba release region or close by, in all flights except those in the polar cap where auroras were seen only near the southern horizon.

Electrostatic two-dimensional numerical simulations of a radially symmetric barium injection experiment demonstrate that ions created by solar UV irradiation are electrostatically bound to the electrons which remain tied to the field lines on which they are created. Two possible instabilities are identified, but neither of them causes the barium plasma cloud to polarize in a way that would permit the plasma to keep up with the neutrals. In a second model, the velocity of the neutrals is allowed to be a function of the azimuthal angle. Here, a portion of the cloud does polarize in a way that allows a portion of the plasma to detach and move outward at the approximate speed of the neutrals. No rapid detachment is found when only the density of the neutrals is given an azimuthal asymmetry.

An accelerator intended to send electron beams upward along an L = 1.24 magnetic field line was flown from a rocket launched from Kauai, Hawaii, on October 15, 1972. Though the intent was to produce several hundred observable auroral streaks in the Southern Hemisphere, imaging instruments operated there aboard jet aircraft detected only a single aurora. Produced by a 0.155-A beam of energy 22.8 keV, the aurora was of expected brightness and had a diameter (210 + or - 50 m) somewhat larger than expected and an altitude (top 116 + or - 2 km; bottom 92 + or - 2 km) higher than expected.

The Alfven critical velocity mechanism for ionization of a neutral gas streaming across the magnetic field has been demonstrated in laboratory experiments. In March 1983, two rocket-borne experiments with Ba and Sr tested the effect in the wall-less laboratory of space from Punto Lobos, Peru, near 430 km altitude. 'Star of Lima' used a conical Ba shaped charge aimed at an instrument payload about 2 km away. Because of rocket overperformance the detonation occurred in partial sunlight, so that less than 21.6 percent of the ionizing UV was present. Particle and field measurements indicate the production of hot electrons and waves in the energy and frequency range that are respectively predicted to produce a cascade of ionization by the Alfven mechanism. However, the ionization fluxes and wave energy density did not reach cascade levels, and optical observations indicate that only 2.5 to 5 x 10 to the 20th Ba ions were produced. A substantial portion and perhaps all of the ionization could have been produced by solar UV. The failure of the Alfven process in this experiment is not well understood.

In January 1975, two barium plasma injection experiments were carried out with rockets launched from Cape Parry, Northwest Territories, Canada, into the upper atmosphere where field lines from the dayside cusp region intersect the ionosphere. One experiment, Tordo 1, took place near the beginning of a worldwide magnetic storm. It became a polar cap experiment almost immediately as convection perpendicular to B moved the fluorescent plasma jet away from the cusp across the polar cap in an antisunward direction. Convection across the polar cap with an average velocity of more than 1 km/s was observed for nearly 40 min until the barium flux tubes encountered large E fields associated with a poleward bulge of the auroral oval near Greenland. Prior to the encounter with the aurora near Greenland there is evidence of upward acceleration of the barium ions while they were in the polar cap. The three-dimensional observations of the plasma orientation and motion give an insight into convection from the cusp region across the polar cap, the orientation of the polar cap magnetic field lines out to several earth radii, the causes of polar cap magnetic perturbations, and parallel acceleration processes.

A barium shaped charge, named Limerick, was released from a rocket launched from Poker Flat Research Range, Alaska, on March 30, 1982, at 1033 UT. The release took place in a small auroral breakup. The jet of ionized barium reached an altitude of 8100 km 14.5 min after release, indicating that there were no parallel electric fields below this altitude. At 8100 km the jet appeared to stop. Analysis shows that the barium at this altitude was effectively removed from the tip. It is concluded that the barium was actually accelerated upward, resulting in a large decrease in the line-of-sight density and hence the optical intensity. The parallel electric potential in the acceleration region must have been greater than 1 kV over an altitude interval of less than 200 km. The acceleration region, although presumably auroral in origin, did not seem to be related to individual auroral structures, but appeared to be a large-scale horizontal structure. The perpendicular electric field below, as deduced from the drift of the barium, was temporally and spatially very uniform and showed no variation related to individual auroral structures passing through.

Magnetograms from Macquarie Island were compared with those from nine Alaskan IGY stations, Fort Churchill, Canada, and Cape Chelyuskin, USSR. The magnetic variations at Macquarie Island were found to correspond remarkably well in universal time with those at several Alaskan stations. On the basis of this study an area lying roughly between Healy and Kotzebue, Alaska, can be defined as the area conjugate magnetically to Macquarie Island.