This series consists of Scientific reports, Technical reports and Final reports issued by the Geophysical Institute on all contracts and grants.
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Telluric, geomagnetic, and auroral activity on Arctic drifting stations and at Pt. Barrow
V. P. Hessler
This report presents results of scaling and analysis of telluric, magnetic and auroral data taken at Point Barrow, and on Arctic drifting stations Charlie, Arlis I and Arlis III. Scalings of hourly range in telluric current activity for Point Barrow are presented for the epoch August 1961 through December 1965. Similar scalings are presented for the 2 to 4 month data recording periods for each of the three drifting stations. Studies of the diurnal variation of telluric current activity with respect to the auroral oval show relatively good correlation. However, the differences suggest the need for more study in relating the telluric activity to the auroral activity and, perhaps, in the delineation of Akasofu’s “approximate” auroral ovals. The relative amplitude of telluric activity at College, Barrow and Charlie is in the order of 13 to 5 to 1. Normal run magnetograms are presented for about one month at each of stations Charlie and Arlis I. At Arlis I several measurements of declination were made as well as a number of measurements of total field, F. The total field measurements were made with a Rubidium vapor magnetometer. At Arlis III the Askamia variograph was equipped with a 6 in/hr chart recorder for comparison with telluric records. Simultaneous N-S, E-W, H and D traces are presented for several polar substorms. An all sky aurora camera was operated on Arlis III to provide data for the analysis of auroral arc drift and orientation with respect to the electric and magnetic disturbance vectors at the surface of the sea. Analysis of the E and H disturbance vectors generally shows the orthogonality required by the plane wave inducing field theory. However, there are marked discrepancies as predicted by Price when the scale values of the inducing field are taken into account. The telluric current in the sea is generally aligned with “systems” of auroral arcs but major differences occur. A study of the northward surge of auroral arcs in relation to the E and H vector activity was made. The E and H disturbance at the surface of the sea begins when the auroral arc arrives at the zenith, but maximum amplitude does not occur until the auroral arc reaches its most northernmost limit of travel. The arcs analyzed did not disappear over the northern horizon.
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Ionospheric drift measurements in the auroral zone
Jerry L. Kisabeth
An investigation of the apparent horizontal ionospheric drifts in the ’90 km’ region and the E-region is presented. The investigation was made using the spaced-receiver method with a frequency of 3.321 MHz at College, Alaska. The structure and random characteristics of the ionospheric irregularities are described. A comparison between the two different levels shows noticeable differences of these properties. A comparison between the ’90 km’ drift measurements and meteor winds, also obtained at College, is presented. Individual wind and drift measurements were very difficult to compare, because of the lack of meteor events. Instead, average winds and drifts were used for the comparison. The results show that during magnetically quiet periods, the comparison is good, whereas during periods of increased magnetic activity the comparison is poor. Periodic fading events observed at College are also discussed.
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Characteristics of Pc-1 events observed at Kotzebue, Point Barrow and College, Alaska
George L. Mason, Richard R. Heacock, and John O. Annexstad
Induction magnetometer data recorded at three Alaskan sites over several years were studied with special attention given to Pc 1-2 micropulsation events. Amplitudes and occurrences of periodically structured Pc 1 events were found to be significantly greater at Kotzebue and College than at Barrow, the more northerly station. Amplitudes and occurrences of unstructured Pc 1-2 events tend to be greatest at Barrow. Inter-site comparisons are made for a complex, large-amplitude interval of Pc 1-2 activity which occurred on March 22-23, 1967. Comparisons of polarization sense at Barrow and College disclosed no meaningful relationship. Most structured Pc 1 events recorded at Kotzebue were also recorded at College, and vice versa, though some large-amplitude events appeared at only one site. The results of the experiment show the desirability for a still closer spacing between recording sites.
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Characteristics of Pc-1 events observed at Kotzebue, Point Barrow and College, Alaska
George L. Mason, Richard R. Heacock, and John O. Annexstad
Induction magnetometer data recorded at three Alaskan sites over several years were studied with special attention given to Pc 1-2 micropulsation events. Amplitudes and occurrences of periodically structured Pc 1 events were found to be significantly greater at Kotzebue and College than at Barrow, the more northerly station. Amplitudes and occurrences of unstructured Pc 1-2 events tend to be greatest at Barrow. Inter-site comparisons are made for a complex, large-amplitude interval of Pc 1-2 activity which occurred on March 22-23, 1967. Comparisons of polarization sense at Barrow and College disclosed no meaningful relationship. Most structured Pc 1 events recorded at Kotzebue were also recorded at College, and vice versa, though some large-amplitude events appeared at only one site. The results of the experiment show the desirability for a still closer spacing between recording sites.
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Geophysical Institute Annual Report 1968-69
University of Alaska Fairbanks. Geophysical Institute
The 1968–69 Geophysical Institute Annual Report presents an overview of the year’s scientific research achievements across the Institute’s disciplines, alongside operational summaries covering finances, administrative changes, and other key activities.
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Hourly values of the auroral electrojet activity index AE for July-December 1957
T. Neil Davis, Carol Echols, and Y. S. Wong
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Hourly values of the auroral electrojet activity index AE for 1963
Carol Echols, Y. S. Wong, and T. Neil Davis
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Geophysical Institute Annual Report 1967-68
University of Alaska Fairbanks. Geophysical Institute
The 1967–68 Geophysical Institute Annual Report presents an overview of the year’s scientific research achievements across the Institute’s disciplines, alongside operational summaries covering finances, administrative changes, and other key activities.
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Hourly values of the auroral electrojet activity index AE for 1960
Y. S. Wong, Carol Echols, and T. Neil Davis
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A Reconnaissance Snow Survey of Interior Alaska
Carl S. Benson
The salient feature of the snow cover in the lowlands of interior Alaska is its low density. This results from prolonged exposure to steep snow temperature gradients with negligible wind action. Strong surface inversions occur frequently and last for weeks at a time in interior Alaska and decouple the lowest air layer in valley bottoms from the air aloft. The dense surface air layer is still and cold (-30 to -40°C is common) and the shallow (less than 1 m thick) snow pack underlying it is subjected to steep temperature gradients because the snow-soil interface temperature rarely goes below -6°C. This transforms most of the snow pack into depth hoar before spring breakup. The density of this depth hoar is generally less than 0.20 g cm-3 which is significantly less than that observed on the Greenland and Antarctic ice sheets or in Alpine snow packs. The boundary between air in the valley bottoms and the air aloft is often sharp. Above the inversion winds are frequent and the snow in this environment is harder and had surface density values in the range of 0.35 to 0.40 g cm-3 whereas the density of the entire snow pack in valley bottoms, only 200-300 m below, is about 0.20 g cm-3. Towns in lowland valleys, such as Fairbanks, lie in the stagnant inversion layer and are subject to air pollution in the winter. The snow cover can be utilized to measure this pollution because it acts as a gigantic filter for fallout particles. A simple measure of impurities in snow is obtained by measuring the specific electrical conductance of its melt water. Tests on a network of top-to-bottom samples of the snow pack taken just before breakup during each of three years, in and around Fairbanks, show values which increase sharply from less than 10 µmho cm-1 in outlying areas to greater than 100 µmho cm-1 downtown. Since this is a reconnaissance study a chronological summary of the field work is presented with the results.
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The June 21, 1967 earthquake series at Fairbanks, Alaska : aftershock locations, depths and magnitudes
Eduard Berg, Larry Gedney, Susumu Kubota, Ken Hanson, and Jurgen Kienle
Aftershock recordings have been obtained to determine the extent of the fracture area which using some 50 shocks, was found to be an area of 10 x 15 km with the major axis roughly oriented in a NW-SE direction. Hypocenter depth varies from 6 to 19 km, with most of the shocks being confined to a depth of 10 to 13 km. It was found that the Jeffreys-Bullen velocities, Vp = 5.56 and Vs = 3.37 km/sec, represent a close approximation of the velocities in the area. Presented also are the telemeter network readings from June 21, 1800 GMT to July 14. These readings include the aftershocks of magnitude 2.5 and upward.
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Large aperture seismic telemetering system for central Alaska
Eduard Berg, Norbert Sperlich, and William Feetham
The Geophysical Institute has established and now operates a large aperture seismic telemeter network in Alaska. At present four stations are operated and two more will be added shortly. The system is described in its technical details, including the remote site equipment and the method of recording at the Geophysical Institute. Without the use of methods for improving signal-to-noise ratio (such as velocity and/or frequency filtering) the sensitivity of the seismic stations for detecting distant earthquakes is similar to that of the U.S.C.&G.S. College Observatory. This sensitivity allows recording of earthquakes down to magnitude 4 (U.S.C.&G.S. magnitude) in the 80° distant range. Epicenter maps for three 1-month periods for interior and coastal Alaska are presented.
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The magnetotelluric coast effect near a dyke or long promontory
J. R. Blake and Daniel W. Swift
The magnetic and telluric fields near a vertical, infinitely deep dyke in an otherwise homogeneous plane medium are calculated. The approximate constancy of the horizontal, surface magnetic field at low frequencies is used as a boundary condition, following Weaver (1963b). Both “polarizations” of the surface electromagnetic field are considered, according to whether the electric or magnetic fields are parallel to the strike. The polarization ellipses of the telluric field and the vertical magnetic field are computed as functions of the conductivity ratio, and dyke thickness, for various observing positions and frequencies, and the fields are compared with similar calculations based on Weaver’s simple fault model. An extension is outlined and the analytical results presented for the case where both ocean and land are underlain by a non-conducting basement. The work of Rankin (1962) is thus extended to cover both polarization orientation of the surface field.
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Variables involved in descriptions of world-wide auroral morphology
T. Neil Davis
Any aspect of auroral morphology is a function of three spatial and one temporal variable and therefore is difficult to describe adequately on a two dimensional sheet of paper. Emphasis is given here to examination of the variables and fixed parameters employed in descriptions of auroral morphology.
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Telluric current micropulsations at the auroral zone
Victor Peter Hessler and Richard R. Heacock
This report presents analysis of individual events and statistical results derived from several years of continuous Pc 1 recording at College, using the telluric current technique. Histograms of occurrence distributions versus Kₚ and versus pulse period, together with sonagrams, justify dividing Pc 1 into two main classes. Class 1 activity has pulse periods mainly shorter than 3 sec, is usually structured, has a pronounced mid-day maximum in occurrence, not much seasonal variation in occurrence, and has little occurrence relationship to Kₚ except for a tendency to be absent when Kₚ is large. Class 2 Pc 1 activity has periods usually longer than 2 sec, is usually unstructured, has a very pronounced afternoon maximum in occurrence at College, a seasonal maximum in summer, and has a positive correlation with Kₚ. Class 1 activity may originate mainly in closed field line regions and Class 2 in open field line regions. Class 1 mid-frequencies tend to rise as Kₚ rises and tend to be higher at night than in the daytime. Average Pc 1 amplitudes maximize in daytime at College as do the occurrences. Thus there is an extreme daytime maximum in summed amplitudes, indicating that the Pc 1 incident energy has a pronounced daytime maximum at College. College sonagrams of Pc 1 events show a great variety of frequency-time forms. Rising frequency periodic structures are most common, but falling frequencies are often seen sometimes superimposed on rising events. At times narrow band “necklaces” are clearly seen. Long duration structured events were observed with durations up to 18 hours. The long events tended to occur only at times of rather low Kₚ.
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Notes on topographic factors affecting the surface wind in Antarctica, with special reference to katabatic winds ; and bibliography
K. B. Mather and G. S. Miller
The topography of the environs of Antarctic stations plays an important part in determining prevailing surface winds. The stations are variously located near the foot of the plateau slope, on offshore islands, on peninsulas, on extensive rock areas, on ice shelves, at sundry latitudes on the plateau and differing distances from the coast. This report is mainly a collection of notes on the topographic factors likely to influence the surface wind. Thirty-four sites are considered, including those of present stations and former expeditions. Particular attention is paid to plateau slope and the exposure of the site to katabatic drainage. Wind roses are shown for most stations, in relation to the plateau contours. Meteorological and sastrugi observations made on traverses are used to supplement the station data. The poor information available on plateau contours was a major handicap throughout the work. Some classifications and systematics of Antarctic data are tabulated, including seasonal variations of wind speed and temperature, the diurnal variation of wind speed, wind frequency versus wind direction, the deviation of the predominant wind direction from the azimuth of plateau slope, the wind direction near the front of ice shelves, and the mean annual wind speed in relation to temperature. The overall flow pattern of the surface winds of Antarctica is shown. Much of the information contained in the report is presented in the form of 7 tables and 75 maps and figures. A comprehensive bibliography (169 entries) lists source material for the notes on station topography and winds, and articles relating particularly to katabatic winds. The report does not deal with upper winds or the general circulation.
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Geophysical Institute Annual Report 1966-67
University of Alaska Fairbanks. Geophysical Institute
The 1966–67 Geophysical Institute Annual Report presents an overview of the year’s scientific research achievements across the Institute’s disciplines, alongside operational summaries covering finances, administrative changes, and other key activities.
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Hourly values of the auroral electrojet activity index AE for 1959
Y. S. Wong, Carol Echols, and T. Neil Davis
