Traditional methods of interpretation of the results of magnetic surveys neglect effects due to permanent magnetization. Recent geomagnetic research on the remanent magnetization of rocks has shown this to be unjustified. Moreover techniques now being employed provide better measurements of magnetic field variations than have ordinarily been available in the past. In order to take advantage of these new developments, equations for the magnetic field over a point dipole, a horizontal line of dipoles, a thin dipping sheet, a thick dipping sheet and a sloping step are derived in the cases when both the directions of measurement and polarization are arbitrary. It is found that these directions combine with other properties of the bodies to form parameters, which determine various features of the magnetic anomalies over the bodies. In terms of these combined parameters, it is possible to give expressions for the higher derivatives of the fields over these bodies, and to develop methods of determining the unknown parameters of the bodies when magnetic profiles over them are given. Further, it is shown that the field over four of these bodies treated can be obtained by successive differentiation of a single function. This fact is used in drawing charts for computing values of the fields and their derivatives at points along profiles over any of these bodies. Tables of the higher derivatives are given, as well as graphs showing the position of special points such as peaks and inflection points on the profiles for any direction of polarization and measurement. It is shown how these more general methods may be applied to the interpretation of aeromagnetic surveys, and examples are given, of their use in the analysis of magnetic survey data over the La-Plonge area, Saskatchewan, and Texada Island, British Columbia. In the latter area, the general question of what geological information may be obtained from magnetic data is considered and a comparison is made of aeromagnetic anomalies with structural data obtained from aerial photographs. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Related investigations of irregular, nighttime, type Pi 2 micropulsations were undertaken with regards to the source and occurrence of these geomagnetic fluctuations. In particular, the local times of Pi 2's recorded by a global network of stations, during 1964, were determined. From this, the Pi 2 daily occurrence maximum was observed near 2230 LMT. For this same year (1964), rapid-run magnetograms from Memambetsu, Japan and Wingst, Germany were analyzed. The initial orientation of the impulsive Pi 2 disturbance vectors was observed to be primarily northeast (north-west) before (after) 2230 LMT. These results suggest that Pi 2 source field lines lie near the 2230 LMT meridian. Further investigations of the globally observed Pi 2's were made regarding variations in morphology with magnetic activity. The daily occurrence maximum of Pi 2 was found earlier (later) at 2030 (2330) LMT during intervals of high (low) magnetic activity. In this manner, the longitudinal shift of the Pi 2 source is revealed. A statistical study of solar wind protons observed by Explorer 34 satellite was made during the intervals of high, and of low, magnetic activity. This study showed that the Pi 2 source shift may be due to a change in the solar wind flow direction and/or processes associated with changes in the solar wind proton pressure. Pi 2’s are a train of pulsations having quasi-periods ranging from 40 to 150 seconds and each series lasts about 10 minutes. The periods of Pi 2 micropulsations recorded at Ralston, Canada during 1967 were correlated with simultaneous, Alouette 2 satellite received, VLF radio signals. Some of these VLF emission phenomena, known as 'whistler cutoff’ and 'lower hybrid resonance noise band breakup', indicated the location of the magnetospheric plasmapause. Other emissions, known as ELF, were believed to indicate the plasma sheet inner boundary. The variation of the period of the Pi 2's with the indicated magnetospheric subregion locations showed that Pi 2 period varies systematically with positions of the plasma sheet inner boundary during intervals of magnetic quiescence. The results imply a latitudinal (radial) movement of the Pi 2 source in a region near the plasma sheet inner boundary. Lastly, the rate of Pi 2 occurrence with magnetic activity, during 1964 and 1967, was found to be maximum when the planetary index of magnetic activity, Kp, was 1+ to 2-. The mean Kp index most closely approaches this optimum level during the years of sunspot minimum. Thus, the rate of occurrence result is consistent with the inverse relationship of Pi 2 yearly occurrence with the solar cycle. In summation, the source studies revealed a ‘dynamic’ Pi 2 source, in the sense that it varies both latitudinally and longitudinally. An association was shown between Pi 2 and nightside magnetospheric processes and subregions. The occurrence study indicated that processes generating Pi 2’s are not clear but approach optimum when the Kp level is between 1+ and 2-. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The electromagnetic induction problem is non-linear, and thus is very difficult to solve for all but the simplest symmetries. Because of this, quantitative modelling of the conductivity structure from geomagnetic depth sounding data is expensive and time consuming, and the possibility that the anomaly is produced by channelling of regionally induced currents may invalidate the results. For this reason traditional methods of analysis are generally qualitative in nature, with quantitative information estimated on the basis of simplified models of the anomaly. The theory and assumptions used in these traditional methods are studied in this thesis, and the range of their applicability is investigated. To avoid the current channelling complication, and to also get a linear relation between the model and the data, the problem is reformulated with the subsurface current density as the model parameter, rather than the conductivity. The disadvantage of this formulation is that models that fit the data are very non-unique. The character of this non-uniqueness has been explored using Backus-Gilbert appraisal, and by the construction of unconstrained models. The results indicate that reasonable resolution of the true model's horizontal features is possible, but that vertical resolution will be lacking. To counter this, the infinite range of possible models is constrained by introducing expected physical features of the true model into the model construction algorithm.' This construction algorithm was tested using data generated from a variety of artificial models, and was successful in resolving both the horizontal and vertical positions of the major features in all of them. The algorithm was then used to determine the subsurface current structure for real data taken across the Cascade anomaly in Washington State. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1931. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed December 7, 2009)

Thesis (M. Phil.)--University of Hong Kong, 1973. / Typewritten.

Thesis (M.Phil.)--University of Hong Kong, 1973. / Also available in print.

Thesis (Ph. D.)--University of Wisconsin, 1996. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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