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  • 1
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    Magnetic charts of Canada derived from MAGSAT data (1982)
    American Geophysical Union
    Details
    Publication Date: 1982-04-01
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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  • 2
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    The magnetic poles of the earth. (1982)
    Society of Geomagnetism and Earth, Planetary and Space Sciences
    Details
    Publication Date: 1982-01-01
    Description: The motions of the Earth's magnetic dip poles and geomagnetic poles over the past 400 years are investigated. In addition, relations are sought between geomagnetic and virtual geomagnetic poles over historic times. Since 1750, the secular motion of the dip poles along their paths has been counterclockwise. During this century this secular motion has been directed in a northwest direction with an average velocity of ~ 11 km per year for the north dip pole and ~ 10 km per year for the south dip pole. In 1980, the north dip pole was located at 77.3°N and 101.8°W in the Canadian Archipelago, and the south dip pole at 65.6°S and 139.4°E just off mainland Antarctica. In addition to its secular motion, each dip pole undergoes a diurnal motion caused by ionospheric current systems. This motion, which is clockwise in the north and anticlockwise in the south, may result in a displacement from the unperturbed position of 65 km and 30 km respectively, on an average disturbed day. The average velocity of the north geomagnetic pole during this century is ~ 1 km per year in a northwest direction. It is about a magnitude less for the virtual geomagnetic pole. Both the geomagnetic and virtual geomagnetic pole paths display a clockwise rotation. There is a great deal of uncertainty in our attempt to use virtual geomagnetic poles to extend the geomagnetic pole path back in time to ~7500 B. C. Much of this uncertainty is due to the sparse distribution of archeomagnetic measurements at a given epoch. © 1982, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.
    Print ISSN: 0022-1392
    Topics: Geosciences
    Published by Society of Geomagnetism and Earth, Planetary and Space Sciences
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  • 3
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    Secular variation in North America during historical times (1984)
    Oxford University Press
    Details
    Publication Date: 1984-07-01
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Royal Astronomical Society.
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  • 4
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    Comparison of IGRF models with North American Magnetic data. (1982)
    Society of Geomagnetism and Earth, Planetary and Space Sciences
    Details
    Publication Date: 1982-01-01
    Description: Comparisons of proposed and adopted geomagnetic reference field models are made against North American test data for the period 1965 to 1985. These test data (X, Y, Z, and F) include Canadian map and aeromagnetic data and USGS land-based data. Model values are also tested against predicted component values for 1982 and 1984 derived from 27 magnetic observatories on or near the North American continent. These tests indicate that all candidate models provide an excellent fit to North American test data at epochs 1965, 1970, and 1975. Only the USGS and NASA models fit these data satisfactorily at 1980. The best secular variation models for 1980-1985 appear to be the IGS and USGS models. Finally, our tests indicate that the recently adopted series of reference field models provides a reasonable and satisfactory fit to North American test data. © 1982, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.
    Print ISSN: 0022-1392
    Topics: Geosciences
    Published by Society of Geomagnetism and Earth, Planetary and Space Sciences
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  • 5
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    The reduction, verification and interpretation of MAGSAT magnetic data over Canada (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Analysis of Investigator B tapes was extended to use a statistical screening of individual data points in each grid cell over the map area. The mean value of data from each cell was computed and all data values more than 4nT from the mean were rejected. The revised mean and standard deviation was computed. The average standard deviation for all map grid cells was 1.4nT for the scalar anomaly map and about 2nT for the vector component anomaly maps. At this stage, the grid cell is larger and spatial resolution lower for the vector maps than for the scalar maps, because the vector components are considerably more disturbed and more data points were rejected. An approach for altitude adjustment is in progress so that corrections can be made and data reduction procede. To evaluate the use of scalar and vector MAGSAT data for the production of regional magnetic charts, charts of the north, east, vertical, and scalar field derived from MAGSAT and from Canadian aeromagnetic data were compared. It appears possible to retrieve crustal signals from the horizontal vector components despite external disturbance fields at high latitude.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E82-10301 , NASA-CR-168876 , NAS 1.26:168876 , PR-4
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    NASA TECHNICAL REPORTS
  • 6
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    The reduction, verification and interpretation of MAGSAT magnetic data over Canada (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Correlations between the MAGSAT scalar anomaly map produced at the Earth Physics ranch and other geophysical and geological data reveal relationships between high magnetic field and some metamorphic grade shields, as well as between low magnetic field and shield regions of lower metamorphic grade. An intriguing contrast exists between the broad low anomaly field over the Nasen-Gakkel Ridge (a spreading plate margin) and the high anomaly field over Iceland (part of a spreading margin). Both regions have high heat flow, and presumably thin magnetic crust. This indicates that Iceland is quite anomalous in its magnetic character, and possible similarities with the Alpha Ridge are suggested. Interesting correlations exist between MAGSAT anomalies around the North Atlantic, after reconstructing the fit of continents into a prerifting configuration. These correlations suggest that several orogenies in that region have not completely destroyed an ancient magnetization formed in high grade Precambrian rocks.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E82-10302 , NASA-CR-168877 , NAS 1.26:168877 , PR-5
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    NASA TECHNICAL REPORTS
  • 7
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    The reduction, verification and interpretation of MAGSAT magnetic data over Canada (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Procedures were established to select quiet, least-disturbed MAGSAT data in an effort to study the magnetic field originating in the solid Earth. A preliminary map of scalar field anomalies over Canada and adjacent regions was produced. Data from Fort Churchill magnetic observatory (an auroral zone station) were used in classifying MAGSAT passes as quiet, unsettled, or disturbed. Determinations of long-term quiet levels at Canadian magnetic observatories are being made. For the time interval of each MAGSAT pass, the deviations of the mean hourly values of the magnetic field components are determined from these quiet levels, in particular for Fort Churchill. Primary processing all CHRONINT tapes received to date, involved decoding orbit records, decimating data records, selecting time intervals and latitude intervals, and producing output tapes carrying records with data point time, position and magnetic information. Subsequent processing converts the coordinate system from geocentric to geodetic and removes a reference field.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E82-10130 , NASA-CR-168514 , NAS 1.26:168514 , PR-2
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    NASA TECHNICAL REPORTS
  • 8
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    The reduction, verification and interpretation of Magsat magnetic data over Canada (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Magnetic anomalies of lithospheric origin are weak at Magsat altitudes (20 to 30 nT at most), and are easily masked by much larger effects caused by field-aligned and other currents at high latitudes. Most of Canada lies under the influence of ionospheric currents in the auroral zone and polar cap. A more refined selection of quiet Magsat data allowed a revised scalar magnetic anomaly map of the whole region north of about 40 deg N latitude. Very preliminary vector anomaly maps and absolute vector component maps were derived. The scalar magnitudes show great promise for mapping the total force and anomaly fields. The Z vector data also appear to be good. The horizontal X and Y vector data are seriously contaminated with external fields and maybe other effects.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E82-10006 , NASA-CR-164904 , PR-3
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    NASA TECHNICAL REPORTS
  • 9
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    The reduction, verification and interpretation of MAGSAT magnetic data over Canada (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Consideration is being given to representing the magnetic field in the area 40 deg N to 83 deg N by means of functions in spherical coordinates. A solution to Laplace's equation for the magnetic potential over a restricted area was found, and programming and testing are currently being carried out. Magnetic anomaly modelling is proceeding. The program SPHERE, which was adapted to function correctly on the Cyber computer, is now operational, for deriving gravity and magnetic models in a spherical coordinate system.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E83-10101 , NASA-CR-169677 , NAS 1.26:169677 , PR-7
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  • 10
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    The reduction, verification and interpretation of MAGSAT magnetic data over Canada (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Research into an approach for altitude adjustments for MAGSAT or similar data acquired over a range of altitudes is progressing. The technique shows promise not only in the production of refined anomaly maps but also in the derivation of regional charts of the magnetic elements from satellite and ground data. Correlations between MAGSAT anomalies and other geophysical and geological data are being explored further and quantitative modelling of some features has begun. The form of some anomalies may change as the maps are refined by the technique being developed. Emphasis is being given to the Canadian regions, although analogous features elsewhere are being considered.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E83-10091 , NASA-CR-169601 , NAS 1.26:169601 , PR-6
    Format: application/pdf
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